Patch to handle compressed sections

Patch to handle compressed sections

[Craig Silverstein]

This patch adds support for reading compressed debug sections, as are
produced by the new gold linker when it's run with
--compress-debug-sections=zlib.

(I had a bit of trouble creating the patch file from my VCS, so I hope
it applies cleanly.  I got it to apply by running 'patch -p0 < <file>'
from the top-level gdb directory.)

craig

2008-03-24  Craig Silverstein  <csilvers@google.com>

	* configure.ac (AC_SEARCH_LIBS): Add check for zlib.
	* config.in, configure: Regenerate.
	* dwarf2read.c: Include zlib.h if present.
	(uncompressed_section_size): New.
	(section_is_p): New.
	(dwarf2_locate_sections): Use section_is_p instead of strcmp
	to determine whether a given section has a given name.
	(dwarf2_read_section): Read the compressed section if present
	in the binary.

--- gdb/config.in	2008-03-25 15:53:56.000000000 -0700
+++ gdb/config.in	2008-03-24 15:50:21.000000000 -0700
@@ -472,6 +472,9 @@
 /* Define to 1 if you have the `XML_StopParser' function. */
 #undef HAVE_XML_STOPPARSER
 
+/* Define to 1 if you have the <zlib.h> header file. */
+#undef HAVE_ZLIB_H
+
 /* Define to 1 if your system has the _etext variable. */
 #undef HAVE__ETEXT
 
--- gdb/configure	2008-03-25 15:53:56.000000000 -0700
+++ gdb/configure	2008-03-24 15:50:23.000000000 -0700
@@ -6003,6 +6003,283 @@
 fi
 
 
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+echo "$as_me:$LINENO: checking for library containing zlibVersion" >&5
+echo $ECHO_N "checking for library containing zlibVersion... $ECHO_C" >&6
+if test "${ac_cv_search_zlibVersion+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+ac_cv_search_zlibVersion=no
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="none required"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+if test "$ac_cv_search_zlibVersion" = no; then
+  for ac_lib in z; do
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+    cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="-l$ac_lib"
+break
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+  done
+fi
+LIBS=$ac_func_search_save_LIBS
+fi
+echo "$as_me:$LINENO: result: $ac_cv_search_zlibVersion" >&5
+echo "${ECHO_T}$ac_cv_search_zlibVersion" >&6
+if test "$ac_cv_search_zlibVersion" != no; then
+  test "$ac_cv_search_zlibVersion" = "none required" || LIBS="$ac_cv_search_zlibVersion $LIBS"
+
+for ac_header in zlib.h
+do
+as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+else
+  # Is the header compilable?
+echo "$as_me:$LINENO: checking $ac_header usability" >&5
+echo $ECHO_N "checking $ac_header usability... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+$ac_includes_default
+#include <$ac_header>
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_header_compiler=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+ac_header_compiler=no
+fi
+rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_compiler" >&5
+echo "${ECHO_T}$ac_header_compiler" >&6
+
+# Is the header present?
+echo "$as_me:$LINENO: checking $ac_header presence" >&5
+echo $ECHO_N "checking $ac_header presence... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+#include <$ac_header>
+_ACEOF
+if { (eval echo "$as_me:$LINENO: \"$ac_cpp conftest.$ac_ext\"") >&5
+  (eval $ac_cpp conftest.$ac_ext) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } >/dev/null; then
+  if test -s conftest.err; then
+    ac_cpp_err=$ac_c_preproc_warn_flag
+    ac_cpp_err=$ac_cpp_err$ac_c_werror_flag
+  else
+    ac_cpp_err=
+  fi
+else
+  ac_cpp_err=yes
+fi
+if test -z "$ac_cpp_err"; then
+  ac_header_preproc=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+  ac_header_preproc=no
+fi
+rm -f conftest.err conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_preproc" >&5
+echo "${ECHO_T}$ac_header_preproc" >&6
+
+# So?  What about this header?
+case $ac_header_compiler:$ac_header_preproc:$ac_c_preproc_warn_flag in
+  yes:no: )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&5
+echo "$as_me: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the compiler's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the compiler's result" >&2;}
+    ac_header_preproc=yes
+    ;;
+  no:yes:* )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: present but cannot be compiled" >&5
+echo "$as_me: WARNING: $ac_header: present but cannot be compiled" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     check for missing prerequisite headers?" >&5
+echo "$as_me: WARNING: $ac_header:     check for missing prerequisite headers?" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: see the Autoconf documentation" >&5
+echo "$as_me: WARNING: $ac_header: see the Autoconf documentation" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&5
+echo "$as_me: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the preprocessor's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the preprocessor's result" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: in the future, the compiler will take precedence" >&5
+echo "$as_me: WARNING: $ac_header: in the future, the compiler will take precedence" >&2;}
+    (
+      cat <<\_ASBOX
+## ------------------------------------------ ##
+## Report this to the AC_PACKAGE_NAME lists.  ##
+## ------------------------------------------ ##
+_ASBOX
+    ) |
+      sed "s/^/$as_me: WARNING:     /" >&2
+    ;;
+esac
+echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  eval "$as_ac_Header=\$ac_header_preproc"
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+
+fi
+if test `eval echo '${'$as_ac_Header'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_header" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+
+done
+
+fi
+
+
 # For the TUI, we need enhanced curses functionality.
 #
 # FIXME: kettenis/20040905: We prefer ncurses over the vendor-supplied
--- gdb/configure.ac	2008-03-25 15:53:56.000000000 -0700
+++ gdb/configure.ac	2008-03-24 15:50:25.000000000 -0700
@@ -394,6 +394,9 @@
 # Some systems (e.g. Solaris) have `socketpair' in libsocket.
 AC_SEARCH_LIBS(socketpair, socket)
 
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+AC_SEARCH_LIBS(zlibVersion, z, [AC_CHECK_HEADERS(zlib.h)])
+
 # For the TUI, we need enhanced curses functionality.
 #
 # FIXME: kettenis/20040905: We prefer ncurses over the vendor-supplied
--- gdb/dwarf2read.c	2008-03-25 15:53:56.000000000 -0700
+++ gdb/dwarf2read.c	2008-03-24 17:28:44.000000000 -0700
@@ -50,6 +50,9 @@
 #include "gdb_string.h"
 #include "gdb_assert.h"
 #include <sys/types.h>
+#ifdef HAVE_ZLIB_H
+#include <zlib.h>
+#endif
 
 /* A note on memory usage for this file.
    
@@ -195,6 +198,10 @@
 
 /* names of the debugging sections */
 
+/* Note that if the debugging section has been compressed, it might
+   have a name like .debug_info.zlib.nnnn (where nnn is the
+   uncompressed size).  */
+
 #define INFO_SECTION     ".debug_info"
 #define ABBREV_SECTION   ".debug_abbrev"
 #define LINE_SECTION     ".debug_line"
@@ -1109,6 +1116,40 @@
   return (dwarf_info_section != NULL && dwarf_abbrev_section != NULL);
 }
 
+/* Given a section name like .debug_str.zlib.nnnn, where nnnn is the
+   uncompressed section size, returns nnnn as an unsigned int.  For
+   other sections, returns the size as per bfd_get_section_size.  */
+static unsigned int
+uncompressed_section_size (asection *sectp)
+{
+  unsigned int uncompressed_size = 0;
+  char *compression_type = strchr (sectp->name + 1, '.');
+  if (compression_type != NULL)
+    {
+      char *size_string = strchr (compression_type + 1, '.');
+      char *strtol_error;
+      if (size_string != NULL
+          && size_string[1] != '\0')
+        uncompressed_size = strtoul (size_string + 1, &strtol_error, 10);
+      if (uncompressed_size > 0 && *strtol_error == '\0')
+        return uncompressed_size;
+    }
+  return bfd_get_section_size (sectp);
+}
+
+/* When loading sections, we can either look for the section name,
+ * or for section_name.zlib.nnnn, which indicates a compressed
+ * section.  nnnn is the uncompressed section size.  */
+
+static int
+section_is_p(asection *sectp, const char *name)
+{
+  int name_size = strlen (name);
+  return (strcmp (sectp->name, name) == 0
+          || (strncmp (sectp->name, name, name_size) == 0
+              && sectp->name[name_size] == '.'));
+}
+
 /* This function is mapped across the sections and remembers the
    offset and size of each of the debugging sections we are interested
    in.  */
@@ -1116,63 +1157,63 @@
 static void
 dwarf2_locate_sections (bfd *abfd, asection *sectp, void *ignore_ptr)
 {
-  if (strcmp (sectp->name, INFO_SECTION) == 0)
+  if (section_is_p (sectp, INFO_SECTION))
     {
-      dwarf2_per_objfile->info_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->info_size = uncompressed_section_size (sectp);
       dwarf_info_section = sectp;
     }
-  else if (strcmp (sectp->name, ABBREV_SECTION) == 0)
+  else if (section_is_p (sectp, ABBREV_SECTION))
     {
-      dwarf2_per_objfile->abbrev_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->abbrev_size = uncompressed_section_size (sectp);
       dwarf_abbrev_section = sectp;
     }
-  else if (strcmp (sectp->name, LINE_SECTION) == 0)
+  else if (section_is_p (sectp, LINE_SECTION))
     {
-      dwarf2_per_objfile->line_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->line_size = uncompressed_section_size (sectp);
       dwarf_line_section = sectp;
     }
-  else if (strcmp (sectp->name, PUBNAMES_SECTION) == 0)
+  else if (section_is_p (sectp, PUBNAMES_SECTION))
     {
-      dwarf2_per_objfile->pubnames_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->pubnames_size = uncompressed_section_size (sectp);
       dwarf_pubnames_section = sectp;
     }
-  else if (strcmp (sectp->name, ARANGES_SECTION) == 0)
+  else if (section_is_p (sectp, ARANGES_SECTION))
     {
-      dwarf2_per_objfile->aranges_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->aranges_size = uncompressed_section_size (sectp);
       dwarf_aranges_section = sectp;
     }
-  else if (strcmp (sectp->name, LOC_SECTION) == 0)
+  else if (section_is_p (sectp, LOC_SECTION))
     {
-      dwarf2_per_objfile->loc_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->loc_size = uncompressed_section_size (sectp);
       dwarf_loc_section = sectp;
     }
-  else if (strcmp (sectp->name, MACINFO_SECTION) == 0)
+  else if (section_is_p (sectp, MACINFO_SECTION))
     {
-      dwarf2_per_objfile->macinfo_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->macinfo_size = uncompressed_section_size (sectp);
       dwarf_macinfo_section = sectp;
     }
-  else if (strcmp (sectp->name, STR_SECTION) == 0)
+  else if (section_is_p (sectp, STR_SECTION))
     {
-      dwarf2_per_objfile->str_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->str_size = uncompressed_section_size (sectp);
       dwarf_str_section = sectp;
     }
-  else if (strcmp (sectp->name, FRAME_SECTION) == 0)
+  else if (section_is_p (sectp, FRAME_SECTION))
     {
-      dwarf2_per_objfile->frame_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->frame_size = uncompressed_section_size (sectp);
       dwarf_frame_section = sectp;
     }
-  else if (strcmp (sectp->name, EH_FRAME_SECTION) == 0)
+  else if (section_is_p (sectp, EH_FRAME_SECTION))
     {
       flagword aflag = bfd_get_section_flags (ignore_abfd, sectp);
       if (aflag & SEC_HAS_CONTENTS)
         {
-          dwarf2_per_objfile->eh_frame_size = bfd_get_section_size (sectp);
+          dwarf2_per_objfile->eh_frame_size = uncompressed_section_size (sectp);
           dwarf_eh_frame_section = sectp;
         }
     }
-  else if (strcmp (sectp->name, RANGES_SECTION) == 0)
+  else if (section_is_p (sectp, RANGES_SECTION))
     {
-      dwarf2_per_objfile->ranges_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->ranges_size = uncompressed_section_size (sectp);
       dwarf_ranges_section = sectp;
     }
   
@@ -5234,29 +5275,113 @@
 }
 
 /* Read the contents of the section at OFFSET and of size SIZE from the
-   object file specified by OBJFILE into the objfile_obstack and return it.  */
+   object file specified by OBJFILE into the objfile_obstack and return it.
+   If the section is compressed, uncompress it before returning.  */
 
 gdb_byte *
 dwarf2_read_section (struct objfile *objfile, asection *sectp)
 {
   bfd *abfd = objfile->obfd;
-  gdb_byte *buf, *retbuf;
   bfd_size_type size = bfd_get_section_size (sectp);
+  char *compression_type = NULL;
+  unsigned long uncompressed_size = 0;
 
   if (size == 0)
     return NULL;
 
-  buf = obstack_alloc (&objfile->objfile_obstack, size);
-  retbuf = symfile_relocate_debug_section (abfd, sectp, buf);
-  if (retbuf != NULL)
-    return retbuf;
+  /* If the section is stored compressed, it will have the name
+     .debug_*.zlib.nnnn, where nnnn is the uncompressed size.  */
+  compression_type = strchr (sectp->name + 1, '.');
+  if (compression_type != NULL)
+    {
+      char *size_string = strchr (compression_type + 1, '.');
+      char *strtol_error;
+      if (size_string != NULL
+          && size_string[1] != '\0')
+        uncompressed_size = strtoul (size_string + 1, &strtol_error, 10);
+      if (uncompressed_size == 0 || *strtol_error != '\0')
+        error (_("Dwarf Error: Can't parse size at end of section name '%s'"
+                 " in '%s'"),
+               sectp->name, bfd_get_filename (abfd));
+    }
+
+  /* Handle the case of a normal, not-compressed section.  */
+  if (compression_type == NULL)
+    {
+      gdb_byte *buf = obstack_alloc (&objfile->objfile_obstack, size);
+      /* When debugging .o files, we may need to apply relocations; see
+         http://www.cygwin.com/ml/gdb-patches/2002-04/msg00136.html .
+         We never compress sections in .o files, so we only need to
+         try this when the section is not compressed.  */
+      gdb_byte *retbuf = symfile_relocate_debug_section (abfd, sectp, buf);
+      if (retbuf != NULL)
+        return retbuf;
+
+      if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
+          || bfd_bread (buf, size, abfd) != size)
+        error (_("Dwarf Error: Can't read DWARF data from '%s'"),
+               bfd_get_filename (abfd));
+
+      return buf;
+    }
+
+  /* Handle the case of a section compressed using zlib.  */
+  if (strncmp (compression_type, ".zlib.", sizeof(".zlib.")-1) == 0)
+    {
+#ifndef HAVE_ZLIB_H
+      error (_("Dwarf Error: Can't uncompress zlib-compressed DWARF data "
+               "in '%s'"),
+               bfd_get_filename (abfd));
+#else
+      int rc;
+      gdb_byte *compressed_buffer = xmalloc (size);
+      Bytef *uncompressed_buffer = obstack_alloc (&objfile->objfile_obstack,
+                                                  uncompressed_size);
+      z_stream strm;
+
+      if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
+          || bfd_bread (compressed_buffer, size, abfd) != size)
+        error (_("Dwarf Error: Can't read DWARF data from '%s'"),
+               bfd_get_filename (abfd));
+
+      /* It is possible the section consists of several compressed
+         buffers concatenated together, so we uncompress in a loop.  */
+      strm.zalloc = NULL;
+      strm.zfree = NULL;
+      strm.opaque = NULL;
+      strm.next_in = (Bytef*)compressed_buffer;
+      strm.avail_in = size;
+      strm.avail_out = uncompressed_size;
+      rc = inflateInit (&strm);
+      while (strm.avail_in > 0)
+        {
+          if (rc != Z_OK)
+            error (_("Dwarf Error: setting up DWARF uncompression in '%s': %d"),
+                   bfd_get_filename (abfd), rc);
+          strm.next_out = (uncompressed_buffer
+                           + (uncompressed_size - strm.avail_out));
+          rc = inflate (&strm, Z_FINISH);
+          if (rc != Z_STREAM_END)
+            error (_("Dwarf Error: zlib error uncompressing from '%s': %d"),
+                   bfd_get_filename (abfd), rc);
+          rc = inflateReset (&strm);
+        }
+      rc = inflateEnd (&strm);
+      if (rc != Z_OK
+          || strm.avail_out != 0)
+        error (_("Dwarf Error: concluding DWARF uncompression in '%s': %d"),
+               bfd_get_filename (abfd), rc);
 
-  if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
-      || bfd_bread (buf, size, abfd) != size)
-    error (_("Dwarf Error: Can't read DWARF data from '%s'"),
-	   bfd_get_filename (abfd));
+      xfree (compressed_buffer);
+      return uncompressed_buffer;
+#endif
+    }
 
-  return buf;
+  /* If we get here, we have an unknown compression type.  */
+  error (_("Dwarf Error: Unknown compression type in section named '%s'"
+           " from '%s'"),
+         sectp->name, bfd_get_filename (abfd));
+  return NULL;
 }
 
 /* In DWARF version 2, the description of the debugging information is
--- /dev/null	1969-12-31 16:00:00.000000000 -0800
+++ gdb/testsuite/gdb.dwarf2/dw2-compressed.S	2008-03-24 15:50:39.000000000 -0700
@@ -0,0 +1,213 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2008 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* This tests that gdb can read compressed sections.  The contents
+   are the same as dw2-basic.S, but the .debug_abbrev section has been
+   comrpessed using zlib.  */
+
+/* Dummy function to provide debug information for.  */
+
+	.text
+	.globl _start
+_start:
+	.int 0
+.Lbegin_text1:
+	.globl func_cu1
+	.type func_cu1, %function
+func_cu1:
+.Lbegin_func_cu1:
+	.int 0
+.Lend_func_cu1:
+	.size func_cu1, .-func_cu1
+.Lend_text1:
+
+/* Debug information */
+
+	.section .debug_info
+.Lcu1_begin:
+	/* CU header */
+	.4byte	.Lcu1_end - .Lcu1_start		/* Length of Compilation Unit */
+.Lcu1_start:
+	.2byte	2				/* DWARF Version */
+	.4byte	.Labbrev1_begin			/* Offset into abbrev section */
+	.byte	4				/* Pointer size */
+
+	/* CU die */
+	.uleb128 1				/* Abbrev: DW_TAG_compile_unit */
+	.4byte	.Lline1_begin			/* DW_AT_stmt_list */
+	.4byte	.Lend_text1			/* DW_AT_high_pc */
+	.4byte	.Lbegin_text1			/* DW_AT_low_pc */
+	.ascii	"file1.txt\0"			/* DW_AT_name */
+	.ascii	"GNU C 3.3.3\0"			/* DW_AT_producer */
+	.byte	1				/* DW_AT_language (C) */
+
+	/* func_cu1 */
+	.uleb128	2			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.byte		1			/* DW_AT_decl_file */
+	.byte		2			/* DW_AT_decl_line */
+	.ascii		"func_cu1\0"		/* DW_AT_name */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+	.4byte		.Lbegin_func_cu1	/* DW_AT_low_pc */
+	.4byte		.Lend_func_cu1		/* DW_AT_high_pc */
+	.byte		1			/* DW_AT_frame_base: length */
+	.byte		0x55			/* DW_AT_frame_base: DW_OP_reg5 */
+
+.Ltype_int:
+	.uleb128	3			/* Abbrev: DW_TAG_base_type */
+	.ascii		"int\0"			/* DW_AT_name */
+	.byte		4			/* DW_AT_byte_size */
+	.byte		5			/* DW_AT_encoding */
+
+	.byte		0			/* End of children of CU */
+
+.Lcu1_end:
+
+/* Line table */
+	.section .debug_line
+.Lline1_begin:
+	.4byte		.Lline1_end - .Lline1_start	/* Initial length */
+.Lline1_start:
+	.2byte		2			/* Version */
+	.4byte		.Lline1_lines - .Lline1_hdr	/* header_length */
+.Lline1_hdr:
+	.byte		1			/* Minimum insn length */
+	.byte		1			/* default_is_stmt */
+	.byte		1			/* line_base */
+ 	.byte		1			/* line_range */
+	.byte		0x10			/* opcode_base */
+
+	/* Standard lengths */
+	.byte		0
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+
+	/* Include directories */
+	.byte		0
+
+	/* File names */
+	.ascii		"file1.txt\0"
+	.uleb128	0
+	.uleb128	0
+	.uleb128	0
+
+	.byte		0
+
+.Lline1_lines:
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lbegin_func_cu1
+
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	3	/* ... to 4 */
+
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		1	/* DW_LNS_copy (second time as an end-of-prologue marker) */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lend_func_cu1
+
+	.byte		0	/* DW_LNE_end_of_sequence */
+	.uleb128	1
+	.byte		1
+
+.Lline1_end:
+
+/* Abbrev table -- compressed */
+	.section .debug_abbrev.zlib.51
+.Labbrev1_begin:
+	.byte		0x78
+	.byte		0x5e
+	.byte		0x63
+	.byte		0x14
+	.byte		0x64
+	.byte		0x14
+	.byte		0x60
+	.byte		0x13
+	.byte		0x62
+	.byte		0x14
+	.byte		0x64
+	.byte		0x64
+	.byte		0xe6
+	.byte		0x50
+	.byte		0xe5
+	.byte		0x10
+	.byte		0xe6
+	.byte		0x66
+	.byte		0x60
+	.byte		0x60
+	.byte		0xd2
+	.byte		0x63
+	.byte		0xb0
+	.byte		0xe7
+	.byte		0xb1
+	.byte		0xe2
+	.byte		0xb6
+	.byte		0xe6
+	.byte		0x66
+	.byte		0xe6
+	.byte		0xf0
+	.byte		0x14
+	.byte		0x16
+	.byte		0x64
+	.byte		0x14
+	.byte		0x62
+	.byte		0x74
+	.byte		0xe0
+	.byte		0x02
+	.byte		0x00
+	.byte		0x25
+	.byte		0x78
+	.byte		0x02
+	.byte		0x81
+	.byte		0x78
+	.byte		0x9c
+	.byte		0x63
+	.byte		0x60
+	.byte		0x60
+	.byte		0x56
+	.byte		0x61
+	.byte		0x60
+	.byte		0xe6
+	.byte		0xe0
+	.byte		0xe6
+	.byte		0xb6
+	.byte		0xe3
+	.byte		0x66
+	.byte		0x00
+	.byte		0x02
+	.byte		0x00
+	.byte		0x04
+	.byte		0x9c
+	.byte		0x00
+	.byte		0x92
--- /dev/null	1969-12-31 16:00:00.000000000 -0800
+++ gdb/testsuite/gdb.dwarf2/dw2-compressed.exp	2008-03-24 15:50:39.000000000 -0700
@@ -0,0 +1,52 @@
+# Copyright 2008 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Minimal DWARF-2 unit test
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+# For now pick a sampling of likely targets.
+if {![istarget *-*-linux*]
+    && ![istarget *-*-gnu*]
+    && ![istarget *-*-elf*]
+    && ![istarget *-*-openbsd*]
+    && ![istarget arm-*-eabi*]
+    && ![istarget powerpc-*-eabi*]} {
+    return 0  
+}
+
+set testfile "dw2-compressed"
+set srcfile ${testfile}.S
+set binfile ${objdir}/${subdir}/${testfile}.x
+
+if  { [gdb_compile "${srcdir}/${subdir}/main.c" "main-ndebug.o" object -g0] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${testfile}.o" object {nodebug}] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${testfile}.o main-ndebug.o -static -nostdlib" "${binfile}" executable {debug}] != "" } {
+    return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+gdb_test "set listsize 1" ""
+gdb_test "list func_cu1" "4\[ \t\]+File 1 Line 4"
+gdb_test "ptype func_cu1" "type = int \\(\\)"

Re: Patch to handle compressed sections

[Thiago Jung Bauermann]

On Tue, 2008-03-25 at 16:04 -0700, Craig Silverstein wrote:
> This patch adds support for reading compressed debug sections, as are
> produced by the new gold linker when it's run with
> --compress-debug-sections=zlib.

Neat. Out of curiosity, does this approach work well in practice? If you
need to compress debug info, it means you are dealing with a very large
amount of it. Isn't it cumbersome for GDB to deal with it later? I
imagine it must be slow to wait for GDB to uncompress and interpret it
all, and it must use a very big amount of memory.

It's a trade-off where you ease the burden on the computer where the
program runs, and permits you to have debuginfo around where you
probably couldn't before, but on the other hand you need a lot of
resources to actually be able to work with that debuginfo in a debug
environment, right?

> +/* Note that if the debugging section has been compressed, it might
> +   have a name like .debug_info.zlib.nnnn (where nnn is the
> +   uncompressed size).  */

I am not as fluent in ELF and DWARF representation as I would like, so
take this for what it's worth:

Encoding this information in the section name looks strange to me. Isn't
it possible to define a new flag in the section's sh_flags to signal
that the section is compressed and then use the first few bytes of the
section contents for the information above?

Or alternatively, create a note section for that? This route might be
easier in that it doesn't raise compatibility concerns, and there's no
immediate need to actually extend the ELF standard.

> +  /* Handle the case of a section compressed using zlib.  */
> +  if (strncmp (compression_type, ".zlib.", sizeof(".zlib.")-1) == 0)
> +    {
> +#ifndef HAVE_ZLIB_H
> +      error (_("Dwarf Error: Can't uncompress zlib-compressed DWARF data "
> +               "in '%s'"),
> +               bfd_get_filename (abfd));
> +#else

I think it's better for this error message to say something along the
lines of "Support for compressed DWARF data is disabled in this copy of
GDB".
-- 
[]'s
Thiago Jung Bauermann
Software Engineer
IBM Linux Technology Center

Re: Patch to handle compressed sections

[Craig Silverstein]

} Neat. Out of curiosity, does this approach work well in practice?

Yes, it seems to work quite well.

} If you need to compress debug info, it means you are dealing with a
} very large amount of it.

This is true.  An example binary we deal with could be about 2G with
debug information, and about 1.3G with the debug information
compressed.

However, we tend to have machines with quite fast processors, and
decompressing the debug information doesn't take very long; at least,
it's on the order of existing gdb startup time (which includes reading
all that data from disk in the first place).  It may even be faster to
read less data from disk and uncompress it, than to just read all the
data from disk in the first place.

I wrote the patch to be extensible to other compression formats in the
future.  One possibility would be to support a compression format that
does not have great compression, but is very fast to decompress.  That
could be used in environments where decompress time is more of a
concern.

} It's a trade-off where you ease the burden on the computer where the
} program runs, and permits you to have debuginfo around where you
} probably couldn't before, but on the other hand you need a lot of
} resources to actually be able to work with that debuginfo in a debug
} environment, right?

I see the trade-off as more of a disk/cpu tradeoff.  For us, the
machines are powerful enough to deal with the uncompressed binaries,
but they take up an awful lot of disk space.  Compressing allows the
binaries to take up less disk, without really affecting run-time
behavior noticeably.

} Encoding this information in the section name looks strange to
} me. Isn't it possible to define a new flag in the section's sh_flags
} to signal that the section is compressed and then use the first few
} bytes of the section contents for the information above?

This was the first thing I tried, but it had -- as you pointed out --
compatibility issues.  In particular, various tools would try to read
a .debug_* section, but not know about the new flag (or the new .note
section, if we implemented it that way), and would complain about a
malformed section.  objdump, if I remember correctly, would complain
about 1000 times per malformed section(!).

I've found these tools deal much better if the section is just missing
entirely (because instead we have a section named .debug_*.zlib.nnnn
instead).

We could compromise and still give the section a different name, like
.debug_info.zlib, and then store the 'nnnn' part in a .note section or
somewhere else, but I didn't see much benefit to that.

} I think it's better for this error message to say something along
} the lines of "Support for compressed DWARF data is disabled in this
} copy of GDB".

Good idea.  I attach a new patch below that's identical except for the
error mesage text.

craig

2008-03-24  Craig Silverstein  <csilvers@google.com>

	* configure.ac (AC_SEARCH_LIBS): Add check for zlib.
	* config.in, configure: Regenerate.
	* dwarf2read.c: Include zlib.h if present.
	(uncompressed_section_size): New.
	(section_is_p): New.
	(dwarf2_locate_sections): Use section_is_p instead of strcmp
	to determine whether a given section has a given name.
	(dwarf2_read_section): Read the compressed section if present
	in the binary.

--- gdb/config.in	2008-03-25 15:53:56.000000000 -0700
+++ gdb/config.in	2008-03-24 15:50:21.000000000 -0700
@@ -472,6 +472,9 @@
 /* Define to 1 if you have the `XML_StopParser' function. */
 #undef HAVE_XML_STOPPARSER
 
+/* Define to 1 if you have the <zlib.h> header file. */
+#undef HAVE_ZLIB_H
+
 /* Define to 1 if your system has the _etext variable. */
 #undef HAVE__ETEXT
 
--- gdb/configure	2008-03-25 15:53:56.000000000 -0700
+++ gdb/configure	2008-03-24 15:50:23.000000000 -0700
@@ -6003,6 +6003,283 @@
 fi
 
 
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+echo "$as_me:$LINENO: checking for library containing zlibVersion" >&5
+echo $ECHO_N "checking for library containing zlibVersion... $ECHO_C" >&6
+if test "${ac_cv_search_zlibVersion+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+ac_cv_search_zlibVersion=no
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="none required"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+if test "$ac_cv_search_zlibVersion" = no; then
+  for ac_lib in z; do
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+    cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="-l$ac_lib"
+break
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+  done
+fi
+LIBS=$ac_func_search_save_LIBS
+fi
+echo "$as_me:$LINENO: result: $ac_cv_search_zlibVersion" >&5
+echo "${ECHO_T}$ac_cv_search_zlibVersion" >&6
+if test "$ac_cv_search_zlibVersion" != no; then
+  test "$ac_cv_search_zlibVersion" = "none required" || LIBS="$ac_cv_search_zlibVersion $LIBS"
+
+for ac_header in zlib.h
+do
+as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+else
+  # Is the header compilable?
+echo "$as_me:$LINENO: checking $ac_header usability" >&5
+echo $ECHO_N "checking $ac_header usability... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+$ac_includes_default
+#include <$ac_header>
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_header_compiler=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+ac_header_compiler=no
+fi
+rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_compiler" >&5
+echo "${ECHO_T}$ac_header_compiler" >&6
+
+# Is the header present?
+echo "$as_me:$LINENO: checking $ac_header presence" >&5
+echo $ECHO_N "checking $ac_header presence... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+#include <$ac_header>
+_ACEOF
+if { (eval echo "$as_me:$LINENO: \"$ac_cpp conftest.$ac_ext\"") >&5
+  (eval $ac_cpp conftest.$ac_ext) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } >/dev/null; then
+  if test -s conftest.err; then
+    ac_cpp_err=$ac_c_preproc_warn_flag
+    ac_cpp_err=$ac_cpp_err$ac_c_werror_flag
+  else
+    ac_cpp_err=
+  fi
+else
+  ac_cpp_err=yes
+fi
+if test -z "$ac_cpp_err"; then
+  ac_header_preproc=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+  ac_header_preproc=no
+fi
+rm -f conftest.err conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_preproc" >&5
+echo "${ECHO_T}$ac_header_preproc" >&6
+
+# So?  What about this header?
+case $ac_header_compiler:$ac_header_preproc:$ac_c_preproc_warn_flag in
+  yes:no: )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&5
+echo "$as_me: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the compiler's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the compiler's result" >&2;}
+    ac_header_preproc=yes
+    ;;
+  no:yes:* )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: present but cannot be compiled" >&5
+echo "$as_me: WARNING: $ac_header: present but cannot be compiled" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     check for missing prerequisite headers?" >&5
+echo "$as_me: WARNING: $ac_header:     check for missing prerequisite headers?" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: see the Autoconf documentation" >&5
+echo "$as_me: WARNING: $ac_header: see the Autoconf documentation" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&5
+echo "$as_me: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the preprocessor's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the preprocessor's result" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: in the future, the compiler will take precedence" >&5
+echo "$as_me: WARNING: $ac_header: in the future, the compiler will take precedence" >&2;}
+    (
+      cat <<\_ASBOX
+## ------------------------------------------ ##
+## Report this to the AC_PACKAGE_NAME lists.  ##
+## ------------------------------------------ ##
+_ASBOX
+    ) |
+      sed "s/^/$as_me: WARNING:     /" >&2
+    ;;
+esac
+echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  eval "$as_ac_Header=\$ac_header_preproc"
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+
+fi
+if test `eval echo '${'$as_ac_Header'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_header" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+
+done
+
+fi
+
+
 # For the TUI, we need enhanced curses functionality.
 #
 # FIXME: kettenis/20040905: We prefer ncurses over the vendor-supplied
--- gdb/configure.ac	2008-03-25 15:53:56.000000000 -0700
+++ gdb/configure.ac	2008-03-24 15:50:25.000000000 -0700
@@ -394,6 +394,9 @@
 # Some systems (e.g. Solaris) have `socketpair' in libsocket.
 AC_SEARCH_LIBS(socketpair, socket)
 
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+AC_SEARCH_LIBS(zlibVersion, z, [AC_CHECK_HEADERS(zlib.h)])
+
 # For the TUI, we need enhanced curses functionality.
 #
 # FIXME: kettenis/20040905: We prefer ncurses over the vendor-supplied
--- gdb/dwarf2read.c	2008-03-25 15:53:56.000000000 -0700
+++ gdb/dwarf2read.c	2008-03-24 17:28:44.000000000 -0700
@@ -50,6 +50,9 @@
 #include "gdb_string.h"
 #include "gdb_assert.h"
 #include <sys/types.h>
+#ifdef HAVE_ZLIB_H
+#include <zlib.h>
+#endif
 
 /* A note on memory usage for this file.
    
@@ -195,6 +198,10 @@
 
 /* names of the debugging sections */
 
+/* Note that if the debugging section has been compressed, it might
+   have a name like .debug_info.zlib.nnnn (where nnn is the
+   uncompressed size).  */
+
 #define INFO_SECTION     ".debug_info"
 #define ABBREV_SECTION   ".debug_abbrev"
 #define LINE_SECTION     ".debug_line"
@@ -1109,6 +1116,40 @@
   return (dwarf_info_section != NULL && dwarf_abbrev_section != NULL);
 }
 
+/* Given a section name like .debug_str.zlib.nnnn, where nnnn is the
+   uncompressed section size, returns nnnn as an unsigned int.  For
+   other sections, returns the size as per bfd_get_section_size.  */
+static unsigned int
+uncompressed_section_size (asection *sectp)
+{
+  unsigned int uncompressed_size = 0;
+  char *compression_type = strchr (sectp->name + 1, '.');
+  if (compression_type != NULL)
+    {
+      char *size_string = strchr (compression_type + 1, '.');
+      char *strtol_error;
+      if (size_string != NULL
+          && size_string[1] != '\0')
+        uncompressed_size = strtoul (size_string + 1, &strtol_error, 10);
+      if (uncompressed_size > 0 && *strtol_error == '\0')
+        return uncompressed_size;
+    }
+  return bfd_get_section_size (sectp);
+}
+
+/* When loading sections, we can either look for the section name,
+ * or for section_name.zlib.nnnn, which indicates a compressed
+ * section.  nnnn is the uncompressed section size.  */
+
+static int
+section_is_p(asection *sectp, const char *name)
+{
+  int name_size = strlen (name);
+  return (strcmp (sectp->name, name) == 0
+          || (strncmp (sectp->name, name, name_size) == 0
+              && sectp->name[name_size] == '.'));
+}
+
 /* This function is mapped across the sections and remembers the
    offset and size of each of the debugging sections we are interested
    in.  */
@@ -1116,63 +1157,63 @@
 static void
 dwarf2_locate_sections (bfd *abfd, asection *sectp, void *ignore_ptr)
 {
-  if (strcmp (sectp->name, INFO_SECTION) == 0)
+  if (section_is_p (sectp, INFO_SECTION))
     {
-      dwarf2_per_objfile->info_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->info_size = uncompressed_section_size (sectp);
       dwarf_info_section = sectp;
     }
-  else if (strcmp (sectp->name, ABBREV_SECTION) == 0)
+  else if (section_is_p (sectp, ABBREV_SECTION))
     {
-      dwarf2_per_objfile->abbrev_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->abbrev_size = uncompressed_section_size (sectp);
       dwarf_abbrev_section = sectp;
     }
-  else if (strcmp (sectp->name, LINE_SECTION) == 0)
+  else if (section_is_p (sectp, LINE_SECTION))
     {
-      dwarf2_per_objfile->line_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->line_size = uncompressed_section_size (sectp);
       dwarf_line_section = sectp;
     }
-  else if (strcmp (sectp->name, PUBNAMES_SECTION) == 0)
+  else if (section_is_p (sectp, PUBNAMES_SECTION))
     {
-      dwarf2_per_objfile->pubnames_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->pubnames_size = uncompressed_section_size (sectp);
       dwarf_pubnames_section = sectp;
     }
-  else if (strcmp (sectp->name, ARANGES_SECTION) == 0)
+  else if (section_is_p (sectp, ARANGES_SECTION))
     {
-      dwarf2_per_objfile->aranges_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->aranges_size = uncompressed_section_size (sectp);
       dwarf_aranges_section = sectp;
     }
-  else if (strcmp (sectp->name, LOC_SECTION) == 0)
+  else if (section_is_p (sectp, LOC_SECTION))
     {
-      dwarf2_per_objfile->loc_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->loc_size = uncompressed_section_size (sectp);
       dwarf_loc_section = sectp;
     }
-  else if (strcmp (sectp->name, MACINFO_SECTION) == 0)
+  else if (section_is_p (sectp, MACINFO_SECTION))
     {
-      dwarf2_per_objfile->macinfo_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->macinfo_size = uncompressed_section_size (sectp);
       dwarf_macinfo_section = sectp;
     }
-  else if (strcmp (sectp->name, STR_SECTION) == 0)
+  else if (section_is_p (sectp, STR_SECTION))
     {
-      dwarf2_per_objfile->str_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->str_size = uncompressed_section_size (sectp);
       dwarf_str_section = sectp;
     }
-  else if (strcmp (sectp->name, FRAME_SECTION) == 0)
+  else if (section_is_p (sectp, FRAME_SECTION))
     {
-      dwarf2_per_objfile->frame_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->frame_size = uncompressed_section_size (sectp);
       dwarf_frame_section = sectp;
     }
-  else if (strcmp (sectp->name, EH_FRAME_SECTION) == 0)
+  else if (section_is_p (sectp, EH_FRAME_SECTION))
     {
       flagword aflag = bfd_get_section_flags (ignore_abfd, sectp);
       if (aflag & SEC_HAS_CONTENTS)
         {
-          dwarf2_per_objfile->eh_frame_size = bfd_get_section_size (sectp);
+          dwarf2_per_objfile->eh_frame_size = uncompressed_section_size (sectp);
           dwarf_eh_frame_section = sectp;
         }
     }
-  else if (strcmp (sectp->name, RANGES_SECTION) == 0)
+  else if (section_is_p (sectp, RANGES_SECTION))
     {
-      dwarf2_per_objfile->ranges_size = bfd_get_section_size (sectp);
+      dwarf2_per_objfile->ranges_size = uncompressed_section_size (sectp);
       dwarf_ranges_section = sectp;
     }
   
@@ -5234,29 +5275,113 @@
 }
 
 /* Read the contents of the section at OFFSET and of size SIZE from the
-   object file specified by OBJFILE into the objfile_obstack and return it.  */
+   object file specified by OBJFILE into the objfile_obstack and return it.
+   If the section is compressed, uncompress it before returning.  */
 
 gdb_byte *
 dwarf2_read_section (struct objfile *objfile, asection *sectp)
 {
   bfd *abfd = objfile->obfd;
-  gdb_byte *buf, *retbuf;
   bfd_size_type size = bfd_get_section_size (sectp);
+  char *compression_type = NULL;
+  unsigned long uncompressed_size = 0;
 
   if (size == 0)
     return NULL;
 
-  buf = obstack_alloc (&objfile->objfile_obstack, size);
-  retbuf = symfile_relocate_debug_section (abfd, sectp, buf);
-  if (retbuf != NULL)
-    return retbuf;
+  /* If the section is stored compressed, it will have the name
+     .debug_*.zlib.nnnn, where nnnn is the uncompressed size.  */
+  compression_type = strchr (sectp->name + 1, '.');
+  if (compression_type != NULL)
+    {
+      char *size_string = strchr (compression_type + 1, '.');
+      char *strtol_error;
+      if (size_string != NULL
+          && size_string[1] != '\0')
+        uncompressed_size = strtoul (size_string + 1, &strtol_error, 10);
+      if (uncompressed_size == 0 || *strtol_error != '\0')
+        error (_("Dwarf Error: Can't parse size at end of section name '%s'"
+                 " in '%s'"),
+               sectp->name, bfd_get_filename (abfd));
+    }
+
+  /* Handle the case of a normal, not-compressed section.  */
+  if (compression_type == NULL)
+    {
+      gdb_byte *buf = obstack_alloc (&objfile->objfile_obstack, size);
+      /* When debugging .o files, we may need to apply relocations; see
+         http://www.cygwin.com/ml/gdb-patches/2002-04/msg00136.html .
+         We never compress sections in .o files, so we only need to
+         try this when the section is not compressed.  */
+      gdb_byte *retbuf = symfile_relocate_debug_section (abfd, sectp, buf);
+      if (retbuf != NULL)
+        return retbuf;
+
+      if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
+          || bfd_bread (buf, size, abfd) != size)
+        error (_("Dwarf Error: Can't read DWARF data from '%s'"),
+               bfd_get_filename (abfd));
+
+      return buf;
+    }
+
+  /* Handle the case of a section compressed using zlib.  */
+  if (strncmp (compression_type, ".zlib.", sizeof(".zlib.")-1) == 0)
+    {
+#ifndef HAVE_ZLIB_H
+      error (_("Support for compressed DWARF data (from '%s') is disabled "
+               "in this copy of GDB"),
+               bfd_get_filename (abfd));
+#else
+      int rc;
+      gdb_byte *compressed_buffer = xmalloc (size);
+      Bytef *uncompressed_buffer = obstack_alloc (&objfile->objfile_obstack,
+                                                  uncompressed_size);
+      z_stream strm;
+
+      if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
+          || bfd_bread (compressed_buffer, size, abfd) != size)
+        error (_("Dwarf Error: Can't read DWARF data from '%s'"),
+               bfd_get_filename (abfd));
+
+      /* It is possible the section consists of several compressed
+         buffers concatenated together, so we uncompress in a loop.  */
+      strm.zalloc = NULL;
+      strm.zfree = NULL;
+      strm.opaque = NULL;
+      strm.next_in = (Bytef*)compressed_buffer;
+      strm.avail_in = size;
+      strm.avail_out = uncompressed_size;
+      rc = inflateInit (&strm);
+      while (strm.avail_in > 0)
+        {
+          if (rc != Z_OK)
+            error (_("Dwarf Error: setting up DWARF uncompression in '%s': %d"),
+                   bfd_get_filename (abfd), rc);
+          strm.next_out = (uncompressed_buffer
+                           + (uncompressed_size - strm.avail_out));
+          rc = inflate (&strm, Z_FINISH);
+          if (rc != Z_STREAM_END)
+            error (_("Dwarf Error: zlib error uncompressing from '%s': %d"),
+                   bfd_get_filename (abfd), rc);
+          rc = inflateReset (&strm);
+        }
+      rc = inflateEnd (&strm);
+      if (rc != Z_OK
+          || strm.avail_out != 0)
+        error (_("Dwarf Error: concluding DWARF uncompression in '%s': %d"),
+               bfd_get_filename (abfd), rc);
 
-  if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
-      || bfd_bread (buf, size, abfd) != size)
-    error (_("Dwarf Error: Can't read DWARF data from '%s'"),
-	   bfd_get_filename (abfd));
+      xfree (compressed_buffer);
+      return uncompressed_buffer;
+#endif
+    }
 
-  return buf;
+  /* If we get here, we have an unknown compression type.  */
+  error (_("Dwarf Error: Unknown compression type in section named '%s'"
+           " from '%s'"),
+         sectp->name, bfd_get_filename (abfd));
+  return NULL;
 }
 
 /* In DWARF version 2, the description of the debugging information is
--- /dev/null	1969-12-31 16:00:00.000000000 -0800
+++ gdb/testsuite/gdb.dwarf2/dw2-compressed.S	2008-03-24 15:50:39.000000000 -0700
@@ -0,0 +1,213 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2008 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* This tests that gdb can read compressed sections.  The contents
+   are the same as dw2-basic.S, but the .debug_abbrev section has been
+   comrpessed using zlib.  */
+
+/* Dummy function to provide debug information for.  */
+
+	.text
+	.globl _start
+_start:
+	.int 0
+.Lbegin_text1:
+	.globl func_cu1
+	.type func_cu1, %function
+func_cu1:
+.Lbegin_func_cu1:
+	.int 0
+.Lend_func_cu1:
+	.size func_cu1, .-func_cu1
+.Lend_text1:
+
+/* Debug information */
+
+	.section .debug_info
+.Lcu1_begin:
+	/* CU header */
+	.4byte	.Lcu1_end - .Lcu1_start		/* Length of Compilation Unit */
+.Lcu1_start:
+	.2byte	2				/* DWARF Version */
+	.4byte	.Labbrev1_begin			/* Offset into abbrev section */
+	.byte	4				/* Pointer size */
+
+	/* CU die */
+	.uleb128 1				/* Abbrev: DW_TAG_compile_unit */
+	.4byte	.Lline1_begin			/* DW_AT_stmt_list */
+	.4byte	.Lend_text1			/* DW_AT_high_pc */
+	.4byte	.Lbegin_text1			/* DW_AT_low_pc */
+	.ascii	"file1.txt\0"			/* DW_AT_name */
+	.ascii	"GNU C 3.3.3\0"			/* DW_AT_producer */
+	.byte	1				/* DW_AT_language (C) */
+
+	/* func_cu1 */
+	.uleb128	2			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.byte		1			/* DW_AT_decl_file */
+	.byte		2			/* DW_AT_decl_line */
+	.ascii		"func_cu1\0"		/* DW_AT_name */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+	.4byte		.Lbegin_func_cu1	/* DW_AT_low_pc */
+	.4byte		.Lend_func_cu1		/* DW_AT_high_pc */
+	.byte		1			/* DW_AT_frame_base: length */
+	.byte		0x55			/* DW_AT_frame_base: DW_OP_reg5 */
+
+.Ltype_int:
+	.uleb128	3			/* Abbrev: DW_TAG_base_type */
+	.ascii		"int\0"			/* DW_AT_name */
+	.byte		4			/* DW_AT_byte_size */
+	.byte		5			/* DW_AT_encoding */
+
+	.byte		0			/* End of children of CU */
+
+.Lcu1_end:
+
+/* Line table */
+	.section .debug_line
+.Lline1_begin:
+	.4byte		.Lline1_end - .Lline1_start	/* Initial length */
+.Lline1_start:
+	.2byte		2			/* Version */
+	.4byte		.Lline1_lines - .Lline1_hdr	/* header_length */
+.Lline1_hdr:
+	.byte		1			/* Minimum insn length */
+	.byte		1			/* default_is_stmt */
+	.byte		1			/* line_base */
+ 	.byte		1			/* line_range */
+	.byte		0x10			/* opcode_base */
+
+	/* Standard lengths */
+	.byte		0
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+
+	/* Include directories */
+	.byte		0
+
+	/* File names */
+	.ascii		"file1.txt\0"
+	.uleb128	0
+	.uleb128	0
+	.uleb128	0
+
+	.byte		0
+
+.Lline1_lines:
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lbegin_func_cu1
+
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	3	/* ... to 4 */
+
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		1	/* DW_LNS_copy (second time as an end-of-prologue marker) */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lend_func_cu1
+
+	.byte		0	/* DW_LNE_end_of_sequence */
+	.uleb128	1
+	.byte		1
+
+.Lline1_end:
+
+/* Abbrev table -- compressed */
+	.section .debug_abbrev.zlib.51
+.Labbrev1_begin:
+	.byte		0x78
+	.byte		0x5e
+	.byte		0x63
+	.byte		0x14
+	.byte		0x64
+	.byte		0x14
+	.byte		0x60
+	.byte		0x13
+	.byte		0x62
+	.byte		0x14
+	.byte		0x64
+	.byte		0x64
+	.byte		0xe6
+	.byte		0x50
+	.byte		0xe5
+	.byte		0x10
+	.byte		0xe6
+	.byte		0x66
+	.byte		0x60
+	.byte		0x60
+	.byte		0xd2
+	.byte		0x63
+	.byte		0xb0
+	.byte		0xe7
+	.byte		0xb1
+	.byte		0xe2
+	.byte		0xb6
+	.byte		0xe6
+	.byte		0x66
+	.byte		0xe6
+	.byte		0xf0
+	.byte		0x14
+	.byte		0x16
+	.byte		0x64
+	.byte		0x14
+	.byte		0x62
+	.byte		0x74
+	.byte		0xe0
+	.byte		0x02
+	.byte		0x00
+	.byte		0x25
+	.byte		0x78
+	.byte		0x02
+	.byte		0x81
+	.byte		0x78
+	.byte		0x9c
+	.byte		0x63
+	.byte		0x60
+	.byte		0x60
+	.byte		0x56
+	.byte		0x61
+	.byte		0x60
+	.byte		0xe6
+	.byte		0xe0
+	.byte		0xe6
+	.byte		0xb6
+	.byte		0xe3
+	.byte		0x66
+	.byte		0x00
+	.byte		0x02
+	.byte		0x00
+	.byte		0x04
+	.byte		0x9c
+	.byte		0x00
+	.byte		0x92
--- /dev/null	1969-12-31 16:00:00.000000000 -0800
+++ gdb/testsuite/gdb.dwarf2/dw2-compressed.exp	2008-03-24 15:50:39.000000000 -0700
@@ -0,0 +1,52 @@
+# Copyright 2008 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Minimal DWARF-2 unit test
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+# For now pick a sampling of likely targets.
+if {![istarget *-*-linux*]
+    && ![istarget *-*-gnu*]
+    && ![istarget *-*-elf*]
+    && ![istarget *-*-openbsd*]
+    && ![istarget arm-*-eabi*]
+    && ![istarget powerpc-*-eabi*]} {
+    return 0  
+}
+
+set testfile "dw2-compressed"
+set srcfile ${testfile}.S
+set binfile ${objdir}/${subdir}/${testfile}.x
+
+if  { [gdb_compile "${srcdir}/${subdir}/main.c" "main-ndebug.o" object -g0] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${testfile}.o" object {nodebug}] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${testfile}.o main-ndebug.o -static -nostdlib" "${binfile}" executable {debug}] != "" } {
+    return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+gdb_test "set listsize 1" ""
+gdb_test "list func_cu1" "4\[ \t\]+File 1 Line 4"
+gdb_test "ptype func_cu1" "type = int \\(\\)"

Re: Patch to handle compressed sections

[Daniel Jacobowitz]

On Wed, Mar 26, 2008 at 10:39:18AM -0700, Craig Silverstein wrote:
> We could compromise and still give the section a different name, like
> .debug_info.zlib, and then store the 'nnnn' part in a .note section or
> somewhere else, but I didn't see much benefit to that.

Or in the beginning of .debug_info.zlib?  (.zdebug_info?)

I've been looking at this and wondering if block compression makes
more sense; that would let an optimized consumer keep less than the
whole decompressed contents in memory.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Patch to handle compressed sections

[Craig Silverstein]

} Or in the beginning of .debug_info.zlib?  (.zdebug_info?)

I thought of that too, but again I didn't see much benefit.  On the
other hand, there is a cost (albeit small): now you have a "format"
for compressed data, with a header section and data to follow, so you
need to codify and document the header format, and deal with issues
like 4-byte vs 8-byte and endianness, and then you'll probably want a
version, and things just get very complicated.  I like the simplicity
of saying the section is just a blob of compressed data.

I feel if we start needing more data stored with a compressed section
than just its uncompressed length, then we can move to
.debug_info.zlib and write a header format to encompass all that data,
at that time.  But it's not really necessary to do that now.  (And,
honestly, I'd like to make it difficult to go that route, since again
it adds complexity to what currently seems like a pretty simple
design.)

} I've been looking at this and wondering if block compression makes
} more sense; that would let an optimized consumer keep less than the
} whole decompressed contents in memory.

The current algorithm supports block compression -- if the section
consists of several compressed blocks appended together, it will
recognize that and correctly decompress.

It's true that right now we always decompress all the blocks when we
read a section, but one could imagine that instead we keep track of
this info on a per-block basis, and only decompress a given block at
need.  I think that would complicate the logic significantly, though,
and don't think it's warranted for this version 1.0 patch.  The
important thing, I think, is that this patch doesn't close off making
such an optimization in the future.

craig

Re: Patch to handle compressed sections

[Daniel Jacobowitz]

On Wed, Mar 26, 2008 at 11:35:38AM -0700, Craig Silverstein wrote:
> } Or in the beginning of .debug_info.zlib?  (.zdebug_info?)
> 
> I thought of that too, but again I didn't see much benefit.  On the
> other hand, there is a cost (albeit small): now you have a "format"
> for compressed data, with a header section and data to follow, so you
> need to codify and document the header format, and deal with issues
> like 4-byte vs 8-byte and endianness, and then you'll probably want a
> version, and things just get very complicated.  I like the simplicity
> of saying the section is just a blob of compressed data.

I think we have to do this.  It's unfriendly to consumers to have the
section have an unpredictable name; pattern matching in GDB is not
hard, but e.g. a script which uses -R .debug_info will now need to
script readelf -WS to find the name of the compressed section.

A magic string ("ZLIB"?) and an 8-byte length should be all the
header we need.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Patch to handle compressed sections

[Craig Silverstein]

} I think we have to do this.  It's unfriendly to consumers to have
} the section have an unpredictable name

Yeah, that's a fair point.  OK, I'll rewrite it.

It's a bit of a pain to change formats -- especially with gold already
released to support the old format -- so I'd like to pass the new
format by you guys before I implement it.

My plan is to name the new sections .zdebug_foo.  They will start with
a 5-byte header that indicates what compression format is being used,
and what version of the format.  For now, only ZLIB1 will be
supported.

Following the ZLIB1 header-field will be an 8-byte length
header-field, in big-endian order -- I know DWARF mostly uses leb128,
but I don't want to add the complexity for people who just want to
parse the header (which, technically, isn't part of dwarf :-) ).
Plus, we don't care much about the space used here.

Following the length will come the content, which is just a blob of
data compressed by zlib.

gdb will be changed to look for .zdebug_foo as an alternate to
.debug_foo, and the section-reading code will decompress such sections
at read-time.

Does this sound like a reasonable plan?  If so, I'll try to get a new
patch later this week.

craig

Re: Patch to handle compressed sections

[Daniel Jacobowitz]

On Tue, Apr 01, 2008 at 05:06:38PM -0700, Craig Silverstein wrote:
> My plan is to name the new sections .zdebug_foo.  They will start with
> a 5-byte header that indicates what compression format is being used,
> and what version of the format.  For now, only ZLIB1 will be
> supported.
> 
> Following the ZLIB1 header-field will be an 8-byte length
> header-field, in big-endian order -- I know DWARF mostly uses leb128,
> but I don't want to add the complexity for people who just want to
> parse the header (which, technically, isn't part of dwarf :-) ).
> Plus, we don't care much about the space used here.
> 
> Following the length will come the content, which is just a blob of
> data compressed by zlib.
> 
> gdb will be changed to look for .zdebug_foo as an alternate to
> .debug_foo, and the section-reading code will decompress such sections
> at read-time.
> 
> Does this sound like a reasonable plan?  If so, I'll try to get a new
> patch later this week.

Yes, it sounds reasonable - give it a few days in case anyone else has
comments?  I would have made different choices, but they're not
inherently superior.

(I'd have used a four-byte magic, and an object-file-endianness 64-bit
size; in particular the four-byte magic makes it easier to visually
see the size in section dumps.)

-- 
Daniel Jacobowitz
CodeSourcery

Re: Patch to handle compressed sections

[Craig Silverstein]

} (I'd have used a four-byte magic, and an object-file-endianness
} 64-bit size; in particular the four-byte magic makes it easier to
} visually see the size in section dumps.)

Four-byte magic is a good point; I'll do that and call this version
ZLIB.  If we ever wanted to add more to the zlib header, I'd just make
a new version called ZLB2 or something, so no big deal.

Object-file-endianness makes sense as well.  Unless I run into
problems, I'll probably do things that way.

Thanks for your feedback!

craig

Re: Patch to handle compressed sections

[Andreas Schwab]

Daniel Jacobowitz <drow@false.org> writes:

> (I'd have used a four-byte magic, and an object-file-endianness 64-bit
> size; in particular the four-byte magic makes it easier to visually
> see the size in section dumps.)

Perhaps an 8-byte magic so that the 64-bit size is aligned.  Or a 4-byte
magic and a 4-byte version.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: Patch to handle compressed sections

[Craig Silverstein]

OK, here's the new patch that holds the size in a header field in the
section, and names sections .zdebug_*.  It's a little uglier than
before since gdb, as it's set up now, wants to know the eventual size
of a section when reading the section headers (without having to read
the section contents), and that's no longer possible.  I just reset
the section size at uncompress-time; it doesn't seem to make a
difference.  In any case, the test suite doesn't show any new
failures ... and the new test passes. :-)

The patch is below.

craig

--cut here--

2008-03-02  Craig Silverstein  <csilvers@google.com>

	* configure.ac (AC_SEARCH_LIBS): Add check for zlib.
	* config.in, configure: Regenerate.
	* dwarf2read.c: Include zlib.h if present.
	Modified *_SECTION macros.
	(section_is_p): New.
	(dwarf2_locate_sections): Use section_is_p instead of strcmp
	(dwarf2_resize_section): New.
	to determine whether a given section has a given name.
	(zlib_decompress_section): New.
	(dwarf2_read_section): Read the compressed section if present
	in the binary.

--- gdb/config.in	2008-04-02 22:03:18.000000000 -0700
+++ gdb/config.in	2008-04-02 20:34:55.330545000 -0700
@@ -472,6 +472,9 @@
 /* Define to 1 if you have the `XML_StopParser' function. */
 #undef HAVE_XML_STOPPARSER
 
+/* Define to 1 if you have the <zlib.h> header file. */
+#undef HAVE_ZLIB_H
+
 /* Define to 1 if your system has the _etext variable. */
 #undef HAVE__ETEXT
 
--- gdb/configure	2008-04-02 22:03:18.000000000 -0700
+++ gdb/configure	2008-04-02 20:35:18.785775000 -0700
@@ -6003,6 +6003,560 @@
 fi
 
 
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+echo "$as_me:$LINENO: checking for library containing zlibVersion" >&5
+echo $ECHO_N "checking for library containing zlibVersion... $ECHO_C" >&6
+if test "${ac_cv_search_zlibVersion+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+ac_cv_search_zlibVersion=no
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="none required"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+if test "$ac_cv_search_zlibVersion" = no; then
+  for ac_lib in z; do
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+    cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="-l$ac_lib"
+break
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+  done
+fi
+LIBS=$ac_func_search_save_LIBS
+fi
+echo "$as_me:$LINENO: result: $ac_cv_search_zlibVersion" >&5
+echo "${ECHO_T}$ac_cv_search_zlibVersion" >&6
+if test "$ac_cv_search_zlibVersion" != no; then
+  test "$ac_cv_search_zlibVersion" = "none required" || LIBS="$ac_cv_search_zlibVersion $LIBS"
+
+for ac_header in zlib.h
+do
+as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+else
+  # Is the header compilable?
+echo "$as_me:$LINENO: checking $ac_header usability" >&5
+echo $ECHO_N "checking $ac_header usability... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+$ac_includes_default
+#include <$ac_header>
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_header_compiler=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+ac_header_compiler=no
+fi
+rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_compiler" >&5
+echo "${ECHO_T}$ac_header_compiler" >&6
+
+# Is the header present?
+echo "$as_me:$LINENO: checking $ac_header presence" >&5
+echo $ECHO_N "checking $ac_header presence... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+#include <$ac_header>
+_ACEOF
+if { (eval echo "$as_me:$LINENO: \"$ac_cpp conftest.$ac_ext\"") >&5
+  (eval $ac_cpp conftest.$ac_ext) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } >/dev/null; then
+  if test -s conftest.err; then
+    ac_cpp_err=$ac_c_preproc_warn_flag
+    ac_cpp_err=$ac_cpp_err$ac_c_werror_flag
+  else
+    ac_cpp_err=
+  fi
+else
+  ac_cpp_err=yes
+fi
+if test -z "$ac_cpp_err"; then
+  ac_header_preproc=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+  ac_header_preproc=no
+fi
+rm -f conftest.err conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_preproc" >&5
+echo "${ECHO_T}$ac_header_preproc" >&6
+
+# So?  What about this header?
+case $ac_header_compiler:$ac_header_preproc:$ac_c_preproc_warn_flag in
+  yes:no: )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&5
+echo "$as_me: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the compiler's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the compiler's result" >&2;}
+    ac_header_preproc=yes
+    ;;
+  no:yes:* )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: present but cannot be compiled" >&5
+echo "$as_me: WARNING: $ac_header: present but cannot be compiled" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     check for missing prerequisite headers?" >&5
+echo "$as_me: WARNING: $ac_header:     check for missing prerequisite headers?" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: see the Autoconf documentation" >&5
+echo "$as_me: WARNING: $ac_header: see the Autoconf documentation" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&5
+echo "$as_me: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the preprocessor's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the preprocessor's result" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: in the future, the compiler will take precedence" >&5
+echo "$as_me: WARNING: $ac_header: in the future, the compiler will take precedence" >&2;}
+    (
+      cat <<\_ASBOX
+## ------------------------------------------ ##
+## Report this to the AC_PACKAGE_NAME lists.  ##
+## ------------------------------------------ ##
+_ASBOX
+    ) |
+      sed "s/^/$as_me: WARNING:     /" >&2
+    ;;
+esac
+echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  eval "$as_ac_Header=\$ac_header_preproc"
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+
+fi
+if test `eval echo '${'$as_ac_Header'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_header" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+
+done
+
+fi
+
+
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+echo "$as_me:$LINENO: checking for library containing zlibVersion" >&5
+echo $ECHO_N "checking for library containing zlibVersion... $ECHO_C" >&6
+if test "${ac_cv_search_zlibVersion+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+ac_cv_search_zlibVersion=no
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="none required"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+if test "$ac_cv_search_zlibVersion" = no; then
+  for ac_lib in z; do
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+    cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="-l$ac_lib"
+break
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+  done
+fi
+LIBS=$ac_func_search_save_LIBS
+fi
+echo "$as_me:$LINENO: result: $ac_cv_search_zlibVersion" >&5
+echo "${ECHO_T}$ac_cv_search_zlibVersion" >&6
+if test "$ac_cv_search_zlibVersion" != no; then
+  test "$ac_cv_search_zlibVersion" = "none required" || LIBS="$ac_cv_search_zlibVersion $LIBS"
+
+for ac_header in zlib.h
+do
+as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+else
+  # Is the header compilable?
+echo "$as_me:$LINENO: checking $ac_header usability" >&5
+echo $ECHO_N "checking $ac_header usability... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+$ac_includes_default
+#include <$ac_header>
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_header_compiler=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+ac_header_compiler=no
+fi
+rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_compiler" >&5
+echo "${ECHO_T}$ac_header_compiler" >&6
+
+# Is the header present?
+echo "$as_me:$LINENO: checking $ac_header presence" >&5
+echo $ECHO_N "checking $ac_header presence... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+#include <$ac_header>
+_ACEOF
+if { (eval echo "$as_me:$LINENO: \"$ac_cpp conftest.$ac_ext\"") >&5
+  (eval $ac_cpp conftest.$ac_ext) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } >/dev/null; then
+  if test -s conftest.err; then
+    ac_cpp_err=$ac_c_preproc_warn_flag
+    ac_cpp_err=$ac_cpp_err$ac_c_werror_flag
+  else
+    ac_cpp_err=
+  fi
+else
+  ac_cpp_err=yes
+fi
+if test -z "$ac_cpp_err"; then
+  ac_header_preproc=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+  ac_header_preproc=no
+fi
+rm -f conftest.err conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_preproc" >&5
+echo "${ECHO_T}$ac_header_preproc" >&6
+
+# So?  What about this header?
+case $ac_header_compiler:$ac_header_preproc:$ac_c_preproc_warn_flag in
+  yes:no: )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&5
+echo "$as_me: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the compiler's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the compiler's result" >&2;}
+    ac_header_preproc=yes
+    ;;
+  no:yes:* )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: present but cannot be compiled" >&5
+echo "$as_me: WARNING: $ac_header: present but cannot be compiled" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     check for missing prerequisite headers?" >&5
+echo "$as_me: WARNING: $ac_header:     check for missing prerequisite headers?" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: see the Autoconf documentation" >&5
+echo "$as_me: WARNING: $ac_header: see the Autoconf documentation" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&5
+echo "$as_me: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the preprocessor's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the preprocessor's result" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: in the future, the compiler will take precedence" >&5
+echo "$as_me: WARNING: $ac_header: in the future, the compiler will take precedence" >&2;}
+    (
+      cat <<\_ASBOX
+## ------------------------------------------ ##
+## Report this to the AC_PACKAGE_NAME lists.  ##
+## ------------------------------------------ ##
+_ASBOX
+    ) |
+      sed "s/^/$as_me: WARNING:     /" >&2
+    ;;
+esac
+echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  eval "$as_ac_Header=\$ac_header_preproc"
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+
+fi
+if test `eval echo '${'$as_ac_Header'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_header" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+
+done
+
+fi
+
+
 # For the TUI, we need enhanced curses functionality.
 #
 # FIXME: kettenis/20040905: We prefer ncurses over the vendor-supplied
--- gdb/configure.ac	2008-04-02 22:03:18.000000000 -0700
+++ gdb/configure.ac	2008-04-02 20:34:57.290232000 -0700
@@ -394,6 +394,9 @@
 # Some systems (e.g. Solaris) have `socketpair' in libsocket.
 AC_SEARCH_LIBS(socketpair, socket)
 
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+AC_SEARCH_LIBS(zlibVersion, z, [AC_CHECK_HEADERS(zlib.h)])
+
 # For the TUI, we need enhanced curses functionality.
 #
 # FIXME: kettenis/20040905: We prefer ncurses over the vendor-supplied
--- gdb/dwarf2read.c	2008-04-02 22:03:18.000000000 -0700
+++ gdb/dwarf2read.c	2008-04-02 21:49:17.578222000 -0700
@@ -50,6 +50,9 @@
 #include "gdb_string.h"
 #include "gdb_assert.h"
 #include <sys/types.h>
+#ifdef HAVE_ZLIB_H
+#include <zlib.h>
+#endif
 
 /* A note on memory usage for this file.
    
@@ -195,17 +198,20 @@
 
 /* names of the debugging sections */
 
-#define INFO_SECTION     ".debug_info"
-#define ABBREV_SECTION   ".debug_abbrev"
-#define LINE_SECTION     ".debug_line"
-#define PUBNAMES_SECTION ".debug_pubnames"
-#define ARANGES_SECTION  ".debug_aranges"
-#define LOC_SECTION      ".debug_loc"
-#define MACINFO_SECTION  ".debug_macinfo"
-#define STR_SECTION      ".debug_str"
-#define RANGES_SECTION   ".debug_ranges"
-#define FRAME_SECTION    ".debug_frame"
-#define EH_FRAME_SECTION ".eh_frame"
+/* Note that if the debugging section has been compressed, it might
+   have a name like .zdebug_info.  */
+
+#define INFO_SECTION     "debug_info"
+#define ABBREV_SECTION   "debug_abbrev"
+#define LINE_SECTION     "debug_line"
+#define PUBNAMES_SECTION "debug_pubnames"
+#define ARANGES_SECTION  "debug_aranges"
+#define LOC_SECTION      "debug_loc"
+#define MACINFO_SECTION  "debug_macinfo"
+#define STR_SECTION      "debug_str"
+#define RANGES_SECTION   "debug_ranges"
+#define FRAME_SECTION    "debug_frame"
+#define EH_FRAME_SECTION "eh_frame"
 
 /* local data types */
 
@@ -1109,6 +1115,18 @@
   return (dwarf_info_section != NULL && dwarf_abbrev_section != NULL);
 }
 
+/* When loading sections, we can either look for ".<name>", or for
+ * ".z<name>", which indicates a compressed section.  */
+
+static int
+section_is_p(asection *sectp, const char *name)
+{
+  return ((sectp->name[0] == '.'
+           && strcmp (sectp->name + 1, name) == 0)
+          || (sectp->name[0] == '.' && sectp->name[1] == 'z'
+              && strcmp (sectp->name + 2, name) == 0));
+}
+
 /* This function is mapped across the sections and remembers the
    offset and size of each of the debugging sections we are interested
    in.  */
@@ -1116,52 +1134,52 @@
 static void
 dwarf2_locate_sections (bfd *abfd, asection *sectp, void *ignore_ptr)
 {
-  if (strcmp (sectp->name, INFO_SECTION) == 0)
+  if (section_is_p (sectp, INFO_SECTION))
     {
       dwarf2_per_objfile->info_size = bfd_get_section_size (sectp);
       dwarf_info_section = sectp;
     }
-  else if (strcmp (sectp->name, ABBREV_SECTION) == 0)
+  else if (section_is_p (sectp, ABBREV_SECTION))
     {
       dwarf2_per_objfile->abbrev_size = bfd_get_section_size (sectp);
       dwarf_abbrev_section = sectp;
     }
-  else if (strcmp (sectp->name, LINE_SECTION) == 0)
+  else if (section_is_p (sectp, LINE_SECTION))
     {
       dwarf2_per_objfile->line_size = bfd_get_section_size (sectp);
       dwarf_line_section = sectp;
     }
-  else if (strcmp (sectp->name, PUBNAMES_SECTION) == 0)
+  else if (section_is_p (sectp, PUBNAMES_SECTION))
     {
       dwarf2_per_objfile->pubnames_size = bfd_get_section_size (sectp);
       dwarf_pubnames_section = sectp;
     }
-  else if (strcmp (sectp->name, ARANGES_SECTION) == 0)
+  else if (section_is_p (sectp, ARANGES_SECTION))
     {
       dwarf2_per_objfile->aranges_size = bfd_get_section_size (sectp);
       dwarf_aranges_section = sectp;
     }
-  else if (strcmp (sectp->name, LOC_SECTION) == 0)
+  else if (section_is_p (sectp, LOC_SECTION))
     {
       dwarf2_per_objfile->loc_size = bfd_get_section_size (sectp);
       dwarf_loc_section = sectp;
     }
-  else if (strcmp (sectp->name, MACINFO_SECTION) == 0)
+  else if (section_is_p (sectp, MACINFO_SECTION))
     {
       dwarf2_per_objfile->macinfo_size = bfd_get_section_size (sectp);
       dwarf_macinfo_section = sectp;
     }
-  else if (strcmp (sectp->name, STR_SECTION) == 0)
+  else if (section_is_p (sectp, STR_SECTION))
     {
       dwarf2_per_objfile->str_size = bfd_get_section_size (sectp);
       dwarf_str_section = sectp;
     }
-  else if (strcmp (sectp->name, FRAME_SECTION) == 0)
+  else if (section_is_p (sectp, FRAME_SECTION))
     {
       dwarf2_per_objfile->frame_size = bfd_get_section_size (sectp);
       dwarf_frame_section = sectp;
     }
-  else if (strcmp (sectp->name, EH_FRAME_SECTION) == 0)
+  else if (section_is_p (sectp, EH_FRAME_SECTION))
     {
       flagword aflag = bfd_get_section_flags (ignore_abfd, sectp);
       if (aflag & SEC_HAS_CONTENTS)
@@ -1170,7 +1188,7 @@
           dwarf_eh_frame_section = sectp;
         }
     }
-  else if (strcmp (sectp->name, RANGES_SECTION) == 0)
+  else if (section_is_p (sectp, RANGES_SECTION))
     {
       dwarf2_per_objfile->ranges_size = bfd_get_section_size (sectp);
       dwarf_ranges_section = sectp;
@@ -1181,6 +1199,40 @@
     dwarf2_per_objfile->has_section_at_zero = 1;
 }
 
+/* This function is called after decompressing a section, so
+   dwarf2_per_objfile can record its new, uncompressed size.  */
+
+static void
+dwarf2_resize_section (asection *sectp, bfd_size_type new_size)
+{
+  if (section_is_p (sectp, INFO_SECTION))
+    dwarf2_per_objfile->info_size = new_size;
+  else if (section_is_p (sectp, ABBREV_SECTION))
+    dwarf2_per_objfile->abbrev_size = new_size;
+  else if (section_is_p (sectp, LINE_SECTION))
+    dwarf2_per_objfile->line_size = new_size;
+  else if (section_is_p (sectp, PUBNAMES_SECTION))
+    dwarf2_per_objfile->pubnames_size = new_size;
+  else if (section_is_p (sectp, ARANGES_SECTION))
+    dwarf2_per_objfile->aranges_size = new_size;
+  else if (section_is_p (sectp, LOC_SECTION))
+    dwarf2_per_objfile->loc_size = new_size;
+  else if (section_is_p (sectp, MACINFO_SECTION))
+    dwarf2_per_objfile->macinfo_size = new_size;
+  else if (section_is_p (sectp, STR_SECTION))
+    dwarf2_per_objfile->str_size = new_size;
+  else if (section_is_p (sectp, FRAME_SECTION))
+    dwarf2_per_objfile->frame_size = new_size;
+  else if (section_is_p (sectp, EH_FRAME_SECTION))
+    dwarf2_per_objfile->eh_frame_size = new_size;
+  else if (section_is_p (sectp, RANGES_SECTION))
+    dwarf2_per_objfile->ranges_size = new_size;
+  else
+    internal_error (__FILE__, __LINE__,
+		    _("dwarf2_resize_section: missing section_is_p check: %s"),
+                    sectp->name);
+}
+
 /* Build a partial symbol table.  */
 
 void
@@ -5236,8 +5288,80 @@
     }
 }
 
+/* Decompress a section that was compressed using zlib.  Store the
+   decompressed buffer, and its size, in OUTBUF and OUTSIZE.  */
+
+static void
+zlib_decompress_section (struct objfile *objfile, asection *sectp,
+                         gdb_byte **outbuf, bfd_size_type *outsize)
+{
+#ifndef HAVE_ZLIB_H
+  error (_("Support for zlib-compressed DWARF data (from '%s') "
+           "is disabled in this copy of GDB"),
+         bfd_get_filename (abfd));
+#else
+  bfd *abfd = objfile->obfd;
+  bfd_size_type compressed_size = bfd_get_section_size (sectp);
+  gdb_byte *compressed_buffer = xmalloc (compressed_size);
+  bfd_size_type uncompressed_size;
+  gdb_byte *uncompressed_buffer;
+  z_stream strm;
+  int rc;
+  int header_size = 12;
+
+  if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
+      || bfd_bread (compressed_buffer, compressed_size, abfd) != compressed_size)
+    error (_("Dwarf Error: Can't read DWARF data from '%s'"),
+           bfd_get_filename (abfd));
+
+  /* Read the zlib header.  In this case, it should be "ZLIB" followed
+     by the uncompressed section size, 8 bytes in big-endian order.  */
+  if (compressed_size < header_size
+      || strncmp (compressed_buffer, "ZLIB", 4) != 0)
+    error (_("Dwarf Error: Corrupt DWARF ZLIB header from '%s'"),
+           bfd_get_filename (abfd));
+  uncompressed_size = read_8_bytes (abfd, compressed_buffer + 4);
+
+  /* It is possible the section consists of several compressed
+     buffers concatenated together, so we uncompress in a loop.  */
+  strm.zalloc = NULL;
+  strm.zfree = NULL;
+  strm.opaque = NULL;
+  strm.avail_in = compressed_size - header_size;
+  strm.next_in = (Bytef*) compressed_buffer + header_size;
+  strm.avail_out = uncompressed_size;
+  uncompressed_buffer = obstack_alloc (&objfile->objfile_obstack,
+                                       uncompressed_size);
+  rc = inflateInit (&strm);
+  while (strm.avail_in > 0)
+    {
+      if (rc != Z_OK)
+        error (_("Dwarf Error: setting up DWARF uncompression in '%s': %d"),
+               bfd_get_filename (abfd), rc);
+      strm.next_out = ((Bytef*) uncompressed_buffer
+                       + (uncompressed_size - strm.avail_out));
+      rc = inflate (&strm, Z_FINISH);
+      if (rc != Z_STREAM_END)
+        error (_("Dwarf Error: zlib error uncompressing from '%s': %d"),
+               bfd_get_filename (abfd), rc);
+      rc = inflateReset (&strm);
+    }
+  rc = inflateEnd (&strm);
+  if (rc != Z_OK
+      || strm.avail_out != 0)
+    error (_("Dwarf Error: concluding DWARF uncompression in '%s': %d"),
+           bfd_get_filename (abfd), rc);
+
+  xfree (compressed_buffer);
+  *outbuf = uncompressed_buffer;
+  *outsize = uncompressed_size;
+#endif
+}
+
+
 /* Read the contents of the section at OFFSET and of size SIZE from the
-   object file specified by OBJFILE into the objfile_obstack and return it.  */
+   object file specified by OBJFILE into the objfile_obstack and return it.
+   If the section is compressed, uncompress it before returning.  */
 
 gdb_byte *
 dwarf2_read_section (struct objfile *objfile, asection *sectp)
@@ -5245,11 +5369,31 @@
   bfd *abfd = objfile->obfd;
   gdb_byte *buf, *retbuf;
   bfd_size_type size = bfd_get_section_size (sectp);
+  unsigned char header[4];
 
   if (size == 0)
     return NULL;
 
+  /* Check if the file has a 4-byte header indicating compression.  */
+  if (size > sizeof (header)
+      && bfd_seek (abfd, sectp->filepos, SEEK_SET) == 0
+      && bfd_bread (header, sizeof (header), abfd) == sizeof (header))
+    {
+      /* Upon decompression, update the buffer and its size.  */
+      if (strncmp (header, "ZLIB", sizeof (header)) == 0)
+        {
+          zlib_decompress_section (objfile, sectp, &buf, &size);
+          dwarf2_resize_section (sectp, size);
+          return buf;
+        }
+    }
+
+  /* If we get here, we are a normal, not-compressed section.  */
   buf = obstack_alloc (&objfile->objfile_obstack, size);
+  /* When debugging .o files, we may need to apply relocations; see
+     http://www.cygwin.com/ml/gdb-patches/2002-04/msg00136.html .
+     We never compress sections in .o files, so we only need to
+     try this when the section is not compressed.  */
   retbuf = symfile_relocate_debug_section (abfd, sectp, buf);
   if (retbuf != NULL)
     return retbuf;
--- /dev/null	2007-10-18 09:27:25.000000000 -0700
+++ gdb/testsuite/gdb.dwarf2/dw2-compressed.S	2008-04-02 21:45:44.205442000 -0700
@@ -0,0 +1,215 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2008 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* This tests that gdb can read compressed sections.  The contents
+   are the same as dw2-basic.S, but the .debug_abbrev section has been
+   comrpessed using zlib.  */
+
+/* Dummy function to provide debug information for.  */
+
+	.text
+	.globl _start
+_start:
+	.int 0
+.Lbegin_text1:
+	.globl func_cu1
+	.type func_cu1, %function
+func_cu1:
+.Lbegin_func_cu1:
+	.int 0
+.Lend_func_cu1:
+	.size func_cu1, .-func_cu1
+.Lend_text1:
+
+/* Debug information */
+
+	.section .debug_info
+.Lcu1_begin:
+	/* CU header */
+	.4byte	.Lcu1_end - .Lcu1_start		/* Length of Compilation Unit */
+.Lcu1_start:
+	.2byte	2				/* DWARF Version */
+	.4byte	.Labbrev1_begin			/* Offset into abbrev section */
+	.byte	4				/* Pointer size */
+
+	/* CU die */
+	.uleb128 1				/* Abbrev: DW_TAG_compile_unit */
+	.4byte	.Lline1_begin			/* DW_AT_stmt_list */
+	.4byte	.Lend_text1			/* DW_AT_high_pc */
+	.4byte	.Lbegin_text1			/* DW_AT_low_pc */
+	.ascii	"file1.txt\0"			/* DW_AT_name */
+	.ascii	"GNU C 3.3.3\0"			/* DW_AT_producer */
+	.byte	1				/* DW_AT_language (C) */
+
+	/* func_cu1 */
+	.uleb128	2			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.byte		1			/* DW_AT_decl_file */
+	.byte		2			/* DW_AT_decl_line */
+	.ascii		"func_cu1\0"		/* DW_AT_name */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+	.4byte		.Lbegin_func_cu1	/* DW_AT_low_pc */
+	.4byte		.Lend_func_cu1		/* DW_AT_high_pc */
+	.byte		1			/* DW_AT_frame_base: length */
+	.byte		0x55			/* DW_AT_frame_base: DW_OP_reg5 */
+
+.Ltype_int:
+	.uleb128	3			/* Abbrev: DW_TAG_base_type */
+	.ascii		"int\0"			/* DW_AT_name */
+	.byte		4			/* DW_AT_byte_size */
+	.byte		5			/* DW_AT_encoding */
+
+	.byte		0			/* End of children of CU */
+
+.Lcu1_end:
+
+/* Line table */
+	.section .debug_line
+.Lline1_begin:
+	.4byte		.Lline1_end - .Lline1_start	/* Initial length */
+.Lline1_start:
+	.2byte		2			/* Version */
+	.4byte		.Lline1_lines - .Lline1_hdr	/* header_length */
+.Lline1_hdr:
+	.byte		1			/* Minimum insn length */
+	.byte		1			/* default_is_stmt */
+	.byte		1			/* line_base */
+ 	.byte		1			/* line_range */
+	.byte		0x10			/* opcode_base */
+
+	/* Standard lengths */
+	.byte		0
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+
+	/* Include directories */
+	.byte		0
+
+	/* File names */
+	.ascii		"file1.txt\0"
+	.uleb128	0
+	.uleb128	0
+	.uleb128	0
+
+	.byte		0
+
+.Lline1_lines:
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lbegin_func_cu1
+
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	3	/* ... to 4 */
+
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		1	/* DW_LNS_copy (second time as an end-of-prologue marker) */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lend_func_cu1
+
+	.byte		0	/* DW_LNE_end_of_sequence */
+	.uleb128	1
+	.byte		1
+
+.Lline1_end:
+
+/* Abbrev table -- compressed */
+	.section .zdebug_abbrev
+.Labbrev1_begin:
+	.ascii		"ZLIB"
+	.8byte		51
+	.byte		0x78
+	.byte		0x5e
+	.byte		0x63
+	.byte		0x14
+	.byte		0x64
+	.byte		0x14
+	.byte		0x60
+	.byte		0x13
+	.byte		0x62
+	.byte		0x14
+	.byte		0x64
+	.byte		0x64
+	.byte		0xe6
+	.byte		0x50
+	.byte		0xe5
+	.byte		0x10
+	.byte		0xe6
+	.byte		0x66
+	.byte		0x60
+	.byte		0x60
+	.byte		0xd2
+	.byte		0x63
+	.byte		0xb0
+	.byte		0xe7
+	.byte		0xb1
+	.byte		0xe2
+	.byte		0xb6
+	.byte		0xe6
+	.byte		0x66
+	.byte		0xe6
+	.byte		0xf0
+	.byte		0x14
+	.byte		0x16
+	.byte		0x64
+	.byte		0x14
+	.byte		0x62
+	.byte		0x74
+	.byte		0xe0
+	.byte		0x02
+	.byte		0x00
+	.byte		0x25
+	.byte		0x78
+	.byte		0x02
+	.byte		0x81
+	.byte		0x78
+	.byte		0x9c
+	.byte		0x63
+	.byte		0x60
+	.byte		0x60
+	.byte		0x56
+	.byte		0x61
+	.byte		0x60
+	.byte		0xe6
+	.byte		0xe0
+	.byte		0xe6
+	.byte		0xb6
+	.byte		0xe3
+	.byte		0x66
+	.byte		0x00
+	.byte		0x02
+	.byte		0x00
+	.byte		0x04
+	.byte		0x9c
+	.byte		0x00
+	.byte		0x92
--- /dev/null	2007-10-18 09:27:25.000000000 -0700
+++ gdb/testsuite/gdb.dwarf2/dw2-compressed.exp	2008-04-02 20:35:20.889410000 -0700
@@ -0,0 +1,52 @@
+# Copyright 2008 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Minimal DWARF-2 unit test
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+# For now pick a sampling of likely targets.
+if {![istarget *-*-linux*]
+    && ![istarget *-*-gnu*]
+    && ![istarget *-*-elf*]
+    && ![istarget *-*-openbsd*]
+    && ![istarget arm-*-eabi*]
+    && ![istarget powerpc-*-eabi*]} {
+    return 0  
+}
+
+set testfile "dw2-compressed"
+set srcfile ${testfile}.S
+set binfile ${objdir}/${subdir}/${testfile}.x
+
+if  { [gdb_compile "${srcdir}/${subdir}/main.c" "main-ndebug.o" object -g0] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${testfile}.o" object {nodebug}] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${testfile}.o main-ndebug.o -static -nostdlib" "${binfile}" executable {debug}] != "" } {
+    return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+gdb_test "set listsize 1" ""
+gdb_test "list func_cu1" "4\[ \t\]+File 1 Line 4"
+gdb_test "ptype func_cu1" "type = int \\(\\)"

Re: Patch to handle compressed sections

[Craig Silverstein]

I'm sorry to do this, but hot on the heels of my last patch comes a
new version.  While trying to implement this in gold, I realized that
gold does not have endianness information handy at the time it's
writing the compressed header.  So I've changed back to writing the
uncompressed size always in big-endian.  New patch below.

craig

--cut here--

2008-04-02  Craig Silverstein  <csilvers@google.com>

	* configure.ac (AC_SEARCH_LIBS): Add check for zlib.
	* config.in, configure: Regenerate.
	* dwarf2read.c: Include zlib.h if present.
	Modified *_SECTION macros.
	(section_is_p): New.
	(dwarf2_locate_sections): Use section_is_p instead of strcmp
	(dwarf2_resize_section): New.
	to determine whether a given section has a given name.
	(zlib_decompress_section): New.
	(dwarf2_read_section): Read the compressed section if present
	in the binary.

--- gdb/config.in	2008-03-25 15:53:56.000000000 -0700
+++ gdb/config.in	2008-04-02 23:32:12.692343000 -0700
@@ -472,6 +472,9 @@
 /* Define to 1 if you have the `XML_StopParser' function. */
 #undef HAVE_XML_STOPPARSER
 
+/* Define to 1 if you have the <zlib.h> header file. */
+#undef HAVE_ZLIB_H
+
 /* Define to 1 if your system has the _etext variable. */
 #undef HAVE__ETEXT
 
--- gdb/configure	2008-03-25 15:53:56.000000000 -0700
+++ gdb/configure	2008-04-02 23:32:13.274013000 -0700
@@ -6003,6 +6003,560 @@
 fi
 
 
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+echo "$as_me:$LINENO: checking for library containing zlibVersion" >&5
+echo $ECHO_N "checking for library containing zlibVersion... $ECHO_C" >&6
+if test "${ac_cv_search_zlibVersion+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+ac_cv_search_zlibVersion=no
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="none required"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+if test "$ac_cv_search_zlibVersion" = no; then
+  for ac_lib in z; do
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+    cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="-l$ac_lib"
+break
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+  done
+fi
+LIBS=$ac_func_search_save_LIBS
+fi
+echo "$as_me:$LINENO: result: $ac_cv_search_zlibVersion" >&5
+echo "${ECHO_T}$ac_cv_search_zlibVersion" >&6
+if test "$ac_cv_search_zlibVersion" != no; then
+  test "$ac_cv_search_zlibVersion" = "none required" || LIBS="$ac_cv_search_zlibVersion $LIBS"
+
+for ac_header in zlib.h
+do
+as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+else
+  # Is the header compilable?
+echo "$as_me:$LINENO: checking $ac_header usability" >&5
+echo $ECHO_N "checking $ac_header usability... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+$ac_includes_default
+#include <$ac_header>
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_header_compiler=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+ac_header_compiler=no
+fi
+rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_compiler" >&5
+echo "${ECHO_T}$ac_header_compiler" >&6
+
+# Is the header present?
+echo "$as_me:$LINENO: checking $ac_header presence" >&5
+echo $ECHO_N "checking $ac_header presence... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+#include <$ac_header>
+_ACEOF
+if { (eval echo "$as_me:$LINENO: \"$ac_cpp conftest.$ac_ext\"") >&5
+  (eval $ac_cpp conftest.$ac_ext) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } >/dev/null; then
+  if test -s conftest.err; then
+    ac_cpp_err=$ac_c_preproc_warn_flag
+    ac_cpp_err=$ac_cpp_err$ac_c_werror_flag
+  else
+    ac_cpp_err=
+  fi
+else
+  ac_cpp_err=yes
+fi
+if test -z "$ac_cpp_err"; then
+  ac_header_preproc=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+  ac_header_preproc=no
+fi
+rm -f conftest.err conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_preproc" >&5
+echo "${ECHO_T}$ac_header_preproc" >&6
+
+# So?  What about this header?
+case $ac_header_compiler:$ac_header_preproc:$ac_c_preproc_warn_flag in
+  yes:no: )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&5
+echo "$as_me: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the compiler's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the compiler's result" >&2;}
+    ac_header_preproc=yes
+    ;;
+  no:yes:* )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: present but cannot be compiled" >&5
+echo "$as_me: WARNING: $ac_header: present but cannot be compiled" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     check for missing prerequisite headers?" >&5
+echo "$as_me: WARNING: $ac_header:     check for missing prerequisite headers?" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: see the Autoconf documentation" >&5
+echo "$as_me: WARNING: $ac_header: see the Autoconf documentation" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&5
+echo "$as_me: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the preprocessor's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the preprocessor's result" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: in the future, the compiler will take precedence" >&5
+echo "$as_me: WARNING: $ac_header: in the future, the compiler will take precedence" >&2;}
+    (
+      cat <<\_ASBOX
+## ------------------------------------------ ##
+## Report this to the AC_PACKAGE_NAME lists.  ##
+## ------------------------------------------ ##
+_ASBOX
+    ) |
+      sed "s/^/$as_me: WARNING:     /" >&2
+    ;;
+esac
+echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  eval "$as_ac_Header=\$ac_header_preproc"
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+
+fi
+if test `eval echo '${'$as_ac_Header'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_header" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+
+done
+
+fi
+
+
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+echo "$as_me:$LINENO: checking for library containing zlibVersion" >&5
+echo $ECHO_N "checking for library containing zlibVersion... $ECHO_C" >&6
+if test "${ac_cv_search_zlibVersion+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+ac_cv_search_zlibVersion=no
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="none required"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+if test "$ac_cv_search_zlibVersion" = no; then
+  for ac_lib in z; do
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+    cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="-l$ac_lib"
+break
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+  done
+fi
+LIBS=$ac_func_search_save_LIBS
+fi
+echo "$as_me:$LINENO: result: $ac_cv_search_zlibVersion" >&5
+echo "${ECHO_T}$ac_cv_search_zlibVersion" >&6
+if test "$ac_cv_search_zlibVersion" != no; then
+  test "$ac_cv_search_zlibVersion" = "none required" || LIBS="$ac_cv_search_zlibVersion $LIBS"
+
+for ac_header in zlib.h
+do
+as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+else
+  # Is the header compilable?
+echo "$as_me:$LINENO: checking $ac_header usability" >&5
+echo $ECHO_N "checking $ac_header usability... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+$ac_includes_default
+#include <$ac_header>
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_header_compiler=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+ac_header_compiler=no
+fi
+rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_compiler" >&5
+echo "${ECHO_T}$ac_header_compiler" >&6
+
+# Is the header present?
+echo "$as_me:$LINENO: checking $ac_header presence" >&5
+echo $ECHO_N "checking $ac_header presence... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+#include <$ac_header>
+_ACEOF
+if { (eval echo "$as_me:$LINENO: \"$ac_cpp conftest.$ac_ext\"") >&5
+  (eval $ac_cpp conftest.$ac_ext) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } >/dev/null; then
+  if test -s conftest.err; then
+    ac_cpp_err=$ac_c_preproc_warn_flag
+    ac_cpp_err=$ac_cpp_err$ac_c_werror_flag
+  else
+    ac_cpp_err=
+  fi
+else
+  ac_cpp_err=yes
+fi
+if test -z "$ac_cpp_err"; then
+  ac_header_preproc=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+  ac_header_preproc=no
+fi
+rm -f conftest.err conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_preproc" >&5
+echo "${ECHO_T}$ac_header_preproc" >&6
+
+# So?  What about this header?
+case $ac_header_compiler:$ac_header_preproc:$ac_c_preproc_warn_flag in
+  yes:no: )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&5
+echo "$as_me: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the compiler's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the compiler's result" >&2;}
+    ac_header_preproc=yes
+    ;;
+  no:yes:* )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: present but cannot be compiled" >&5
+echo "$as_me: WARNING: $ac_header: present but cannot be compiled" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     check for missing prerequisite headers?" >&5
+echo "$as_me: WARNING: $ac_header:     check for missing prerequisite headers?" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: see the Autoconf documentation" >&5
+echo "$as_me: WARNING: $ac_header: see the Autoconf documentation" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&5
+echo "$as_me: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the preprocessor's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the preprocessor's result" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: in the future, the compiler will take precedence" >&5
+echo "$as_me: WARNING: $ac_header: in the future, the compiler will take precedence" >&2;}
+    (
+      cat <<\_ASBOX
+## ------------------------------------------ ##
+## Report this to the AC_PACKAGE_NAME lists.  ##
+## ------------------------------------------ ##
+_ASBOX
+    ) |
+      sed "s/^/$as_me: WARNING:     /" >&2
+    ;;
+esac
+echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  eval "$as_ac_Header=\$ac_header_preproc"
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+
+fi
+if test `eval echo '${'$as_ac_Header'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_header" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+
+done
+
+fi
+
+
 # For the TUI, we need enhanced curses functionality.
 #
 # FIXME: kettenis/20040905: We prefer ncurses over the vendor-supplied
--- gdb/configure.ac	2008-03-25 15:53:56.000000000 -0700
+++ gdb/configure.ac	2008-04-02 23:32:13.718654000 -0700
@@ -394,6 +394,9 @@
 # Some systems (e.g. Solaris) have `socketpair' in libsocket.
 AC_SEARCH_LIBS(socketpair, socket)
 
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+AC_SEARCH_LIBS(zlibVersion, z, [AC_CHECK_HEADERS(zlib.h)])
+
 # For the TUI, we need enhanced curses functionality.
 #
 # FIXME: kettenis/20040905: We prefer ncurses over the vendor-supplied
--- gdb/dwarf2read.c	2008-04-02 22:05:37.000000000 -0700
+++ gdb/dwarf2read.c	2008-04-02 23:38:07.077777000 -0700
@@ -50,6 +50,9 @@
 #include "gdb_string.h"
 #include "gdb_assert.h"
 #include <sys/types.h>
+#ifdef HAVE_ZLIB_H
+#include <zlib.h>
+#endif
 
 /* A note on memory usage for this file.
    
@@ -195,17 +198,20 @@
 
 /* names of the debugging sections */
 
-#define INFO_SECTION     ".debug_info"
-#define ABBREV_SECTION   ".debug_abbrev"
-#define LINE_SECTION     ".debug_line"
-#define PUBNAMES_SECTION ".debug_pubnames"
-#define ARANGES_SECTION  ".debug_aranges"
-#define LOC_SECTION      ".debug_loc"
-#define MACINFO_SECTION  ".debug_macinfo"
-#define STR_SECTION      ".debug_str"
-#define RANGES_SECTION   ".debug_ranges"
-#define FRAME_SECTION    ".debug_frame"
-#define EH_FRAME_SECTION ".eh_frame"
+/* Note that if the debugging section has been compressed, it might
+   have a name like .zdebug_info.  */
+
+#define INFO_SECTION     "debug_info"
+#define ABBREV_SECTION   "debug_abbrev"
+#define LINE_SECTION     "debug_line"
+#define PUBNAMES_SECTION "debug_pubnames"
+#define ARANGES_SECTION  "debug_aranges"
+#define LOC_SECTION      "debug_loc"
+#define MACINFO_SECTION  "debug_macinfo"
+#define STR_SECTION      "debug_str"
+#define RANGES_SECTION   "debug_ranges"
+#define FRAME_SECTION    "debug_frame"
+#define EH_FRAME_SECTION "eh_frame"
 
 /* local data types */
 
@@ -1109,6 +1115,18 @@
   return (dwarf_info_section != NULL && dwarf_abbrev_section != NULL);
 }
 
+/* When loading sections, we can either look for ".<name>", or for
+ * ".z<name>", which indicates a compressed section.  */
+
+static int
+section_is_p(asection *sectp, const char *name)
+{
+  return ((sectp->name[0] == '.'
+           && strcmp (sectp->name + 1, name) == 0)
+          || (sectp->name[0] == '.' && sectp->name[1] == 'z'
+              && strcmp (sectp->name + 2, name) == 0));
+}
+
 /* This function is mapped across the sections and remembers the
    offset and size of each of the debugging sections we are interested
    in.  */
@@ -1116,52 +1134,52 @@
 static void
 dwarf2_locate_sections (bfd *abfd, asection *sectp, void *ignore_ptr)
 {
-  if (strcmp (sectp->name, INFO_SECTION) == 0)
+  if (section_is_p (sectp, INFO_SECTION))
     {
       dwarf2_per_objfile->info_size = bfd_get_section_size (sectp);
       dwarf_info_section = sectp;
     }
-  else if (strcmp (sectp->name, ABBREV_SECTION) == 0)
+  else if (section_is_p (sectp, ABBREV_SECTION))
     {
       dwarf2_per_objfile->abbrev_size = bfd_get_section_size (sectp);
       dwarf_abbrev_section = sectp;
     }
-  else if (strcmp (sectp->name, LINE_SECTION) == 0)
+  else if (section_is_p (sectp, LINE_SECTION))
     {
       dwarf2_per_objfile->line_size = bfd_get_section_size (sectp);
       dwarf_line_section = sectp;
     }
-  else if (strcmp (sectp->name, PUBNAMES_SECTION) == 0)
+  else if (section_is_p (sectp, PUBNAMES_SECTION))
     {
       dwarf2_per_objfile->pubnames_size = bfd_get_section_size (sectp);
       dwarf_pubnames_section = sectp;
     }
-  else if (strcmp (sectp->name, ARANGES_SECTION) == 0)
+  else if (section_is_p (sectp, ARANGES_SECTION))
     {
       dwarf2_per_objfile->aranges_size = bfd_get_section_size (sectp);
       dwarf_aranges_section = sectp;
     }
-  else if (strcmp (sectp->name, LOC_SECTION) == 0)
+  else if (section_is_p (sectp, LOC_SECTION))
     {
       dwarf2_per_objfile->loc_size = bfd_get_section_size (sectp);
       dwarf_loc_section = sectp;
     }
-  else if (strcmp (sectp->name, MACINFO_SECTION) == 0)
+  else if (section_is_p (sectp, MACINFO_SECTION))
     {
       dwarf2_per_objfile->macinfo_size = bfd_get_section_size (sectp);
       dwarf_macinfo_section = sectp;
     }
-  else if (strcmp (sectp->name, STR_SECTION) == 0)
+  else if (section_is_p (sectp, STR_SECTION))
     {
       dwarf2_per_objfile->str_size = bfd_get_section_size (sectp);
       dwarf_str_section = sectp;
     }
-  else if (strcmp (sectp->name, FRAME_SECTION) == 0)
+  else if (section_is_p (sectp, FRAME_SECTION))
     {
       dwarf2_per_objfile->frame_size = bfd_get_section_size (sectp);
       dwarf_frame_section = sectp;
     }
-  else if (strcmp (sectp->name, EH_FRAME_SECTION) == 0)
+  else if (section_is_p (sectp, EH_FRAME_SECTION))
     {
       flagword aflag = bfd_get_section_flags (ignore_abfd, sectp);
       if (aflag & SEC_HAS_CONTENTS)
@@ -1170,7 +1188,7 @@
           dwarf_eh_frame_section = sectp;
         }
     }
-  else if (strcmp (sectp->name, RANGES_SECTION) == 0)
+  else if (section_is_p (sectp, RANGES_SECTION))
     {
       dwarf2_per_objfile->ranges_size = bfd_get_section_size (sectp);
       dwarf_ranges_section = sectp;
@@ -1181,6 +1199,40 @@
     dwarf2_per_objfile->has_section_at_zero = 1;
 }
 
+/* This function is called after decompressing a section, so
+   dwarf2_per_objfile can record its new, uncompressed size.  */
+
+static void
+dwarf2_resize_section (asection *sectp, bfd_size_type new_size)
+{
+  if (section_is_p (sectp, INFO_SECTION))
+    dwarf2_per_objfile->info_size = new_size;
+  else if (section_is_p (sectp, ABBREV_SECTION))
+    dwarf2_per_objfile->abbrev_size = new_size;
+  else if (section_is_p (sectp, LINE_SECTION))
+    dwarf2_per_objfile->line_size = new_size;
+  else if (section_is_p (sectp, PUBNAMES_SECTION))
+    dwarf2_per_objfile->pubnames_size = new_size;
+  else if (section_is_p (sectp, ARANGES_SECTION))
+    dwarf2_per_objfile->aranges_size = new_size;
+  else if (section_is_p (sectp, LOC_SECTION))
+    dwarf2_per_objfile->loc_size = new_size;
+  else if (section_is_p (sectp, MACINFO_SECTION))
+    dwarf2_per_objfile->macinfo_size = new_size;
+  else if (section_is_p (sectp, STR_SECTION))
+    dwarf2_per_objfile->str_size = new_size;
+  else if (section_is_p (sectp, FRAME_SECTION))
+    dwarf2_per_objfile->frame_size = new_size;
+  else if (section_is_p (sectp, EH_FRAME_SECTION))
+    dwarf2_per_objfile->eh_frame_size = new_size;
+  else if (section_is_p (sectp, RANGES_SECTION))
+    dwarf2_per_objfile->ranges_size = new_size;
+  else
+    internal_error (__FILE__, __LINE__,
+		    _("dwarf2_resize_section: missing section_is_p check: %s"),
+                    sectp->name);
+}
+
 /* Build a partial symbol table.  */
 
 void
@@ -5236,8 +5288,87 @@
     }
 }
 
+/* Decompress a section that was compressed using zlib.  Store the
+   decompressed buffer, and its size, in OUTBUF and OUTSIZE.  */
+
+static void
+zlib_decompress_section (struct objfile *objfile, asection *sectp,
+                         gdb_byte **outbuf, bfd_size_type *outsize)
+{
+#ifndef HAVE_ZLIB_H
+  error (_("Support for zlib-compressed DWARF data (from '%s') "
+           "is disabled in this copy of GDB"),
+         bfd_get_filename (abfd));
+#else
+  bfd *abfd = objfile->obfd;
+  bfd_size_type compressed_size = bfd_get_section_size (sectp);
+  gdb_byte *compressed_buffer = xmalloc (compressed_size);
+  bfd_size_type uncompressed_size;
+  gdb_byte *uncompressed_buffer;
+  z_stream strm;
+  int rc;
+  int header_size = 12;
+
+  if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
+      || bfd_bread (compressed_buffer, compressed_size, abfd) != compressed_size)
+    error (_("Dwarf Error: Can't read DWARF data from '%s'"),
+           bfd_get_filename (abfd));
+
+  /* Read the zlib header.  In this case, it should be "ZLIB" followed
+     by the uncompressed section size, 8 bytes in big-endian order.  */
+  if (compressed_size < header_size
+      || strncmp (compressed_buffer, "ZLIB", 4) != 0)
+    error (_("Dwarf Error: Corrupt DWARF ZLIB header from '%s'"),
+           bfd_get_filename (abfd));
+  uncompressed_size = compressed_buffer[4]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[5]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[6]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[7]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[8]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[9]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[10]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[11];
+
+  /* It is possible the section consists of several compressed
+     buffers concatenated together, so we uncompress in a loop.  */
+  strm.zalloc = NULL;
+  strm.zfree = NULL;
+  strm.opaque = NULL;
+  strm.avail_in = compressed_size - header_size;
+  strm.next_in = (Bytef*) compressed_buffer + header_size;
+  strm.avail_out = uncompressed_size;
+  uncompressed_buffer = obstack_alloc (&objfile->objfile_obstack,
+                                       uncompressed_size);
+  rc = inflateInit (&strm);
+  while (strm.avail_in > 0)
+    {
+      if (rc != Z_OK)
+        error (_("Dwarf Error: setting up DWARF uncompression in '%s': %d"),
+               bfd_get_filename (abfd), rc);
+      strm.next_out = ((Bytef*) uncompressed_buffer
+                       + (uncompressed_size - strm.avail_out));
+      rc = inflate (&strm, Z_FINISH);
+      if (rc != Z_STREAM_END)
+        error (_("Dwarf Error: zlib error uncompressing from '%s': %d"),
+               bfd_get_filename (abfd), rc);
+      rc = inflateReset (&strm);
+    }
+  rc = inflateEnd (&strm);
+  if (rc != Z_OK
+      || strm.avail_out != 0)
+    error (_("Dwarf Error: concluding DWARF uncompression in '%s': %d"),
+           bfd_get_filename (abfd), rc);
+
+  xfree (compressed_buffer);
+  *outbuf = uncompressed_buffer;
+  *outsize = uncompressed_size;
+#endif
+}
+
+
 /* Read the contents of the section at OFFSET and of size SIZE from the
-   object file specified by OBJFILE into the objfile_obstack and return it.  */
+   object file specified by OBJFILE into the objfile_obstack and return it.
+   If the section is compressed, uncompress it before returning.  */
 
 gdb_byte *
 dwarf2_read_section (struct objfile *objfile, asection *sectp)
@@ -5245,11 +5376,31 @@
   bfd *abfd = objfile->obfd;
   gdb_byte *buf, *retbuf;
   bfd_size_type size = bfd_get_section_size (sectp);
+  unsigned char header[4];
 
   if (size == 0)
     return NULL;
 
+  /* Check if the file has a 4-byte header indicating compression.  */
+  if (size > sizeof (header)
+      && bfd_seek (abfd, sectp->filepos, SEEK_SET) == 0
+      && bfd_bread (header, sizeof (header), abfd) == sizeof (header))
+    {
+      /* Upon decompression, update the buffer and its size.  */
+      if (strncmp (header, "ZLIB", sizeof (header)) == 0)
+        {
+          zlib_decompress_section (objfile, sectp, &buf, &size);
+          dwarf2_resize_section (sectp, size);
+          return buf;
+        }
+    }
+
+  /* If we get here, we are a normal, not-compressed section.  */
   buf = obstack_alloc (&objfile->objfile_obstack, size);
+  /* When debugging .o files, we may need to apply relocations; see
+     http://www.cygwin.com/ml/gdb-patches/2002-04/msg00136.html .
+     We never compress sections in .o files, so we only need to
+     try this when the section is not compressed.  */
   retbuf = symfile_relocate_debug_section (abfd, sectp, buf);
   if (retbuf != NULL)
     return retbuf;
--- /dev/null	2007-10-18 09:27:25.000000000 -0700
+++ gdb/testsuite/gdb.dwarf2/dw2-compressed.S	2008-04-02 23:39:04.480179000 -0700
@@ -0,0 +1,218 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2008 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* This tests that gdb can read compressed sections.  The contents
+   are the same as dw2-basic.S, but the .debug_abbrev section has been
+   comrpessed using zlib.  */
+
+/* Dummy function to provide debug information for.  */
+
+	.text
+	.globl _start
+_start:
+	.int 0
+.Lbegin_text1:
+	.globl func_cu1
+	.type func_cu1, %function
+func_cu1:
+.Lbegin_func_cu1:
+	.int 0
+.Lend_func_cu1:
+	.size func_cu1, .-func_cu1
+.Lend_text1:
+
+/* Debug information */
+
+	.section .debug_info
+.Lcu1_begin:
+	/* CU header */
+	.4byte	.Lcu1_end - .Lcu1_start		/* Length of Compilation Unit */
+.Lcu1_start:
+	.2byte	2				/* DWARF Version */
+	.4byte	.Labbrev1_begin			/* Offset into abbrev section */
+	.byte	4				/* Pointer size */
+
+	/* CU die */
+	.uleb128 1				/* Abbrev: DW_TAG_compile_unit */
+	.4byte	.Lline1_begin			/* DW_AT_stmt_list */
+	.4byte	.Lend_text1			/* DW_AT_high_pc */
+	.4byte	.Lbegin_text1			/* DW_AT_low_pc */
+	.ascii	"file1.txt\0"			/* DW_AT_name */
+	.ascii	"GNU C 3.3.3\0"			/* DW_AT_producer */
+	.byte	1				/* DW_AT_language (C) */
+
+	/* func_cu1 */
+	.uleb128	2			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.byte		1			/* DW_AT_decl_file */
+	.byte		2			/* DW_AT_decl_line */
+	.ascii		"func_cu1\0"		/* DW_AT_name */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+	.4byte		.Lbegin_func_cu1	/* DW_AT_low_pc */
+	.4byte		.Lend_func_cu1		/* DW_AT_high_pc */
+	.byte		1			/* DW_AT_frame_base: length */
+	.byte		0x55			/* DW_AT_frame_base: DW_OP_reg5 */
+
+.Ltype_int:
+	.uleb128	3			/* Abbrev: DW_TAG_base_type */
+	.ascii		"int\0"			/* DW_AT_name */
+	.byte		4			/* DW_AT_byte_size */
+	.byte		5			/* DW_AT_encoding */
+
+	.byte		0			/* End of children of CU */
+
+.Lcu1_end:
+
+/* Line table */
+	.section .debug_line
+.Lline1_begin:
+	.4byte		.Lline1_end - .Lline1_start	/* Initial length */
+.Lline1_start:
+	.2byte		2			/* Version */
+	.4byte		.Lline1_lines - .Lline1_hdr	/* header_length */
+.Lline1_hdr:
+	.byte		1			/* Minimum insn length */
+	.byte		1			/* default_is_stmt */
+	.byte		1			/* line_base */
+ 	.byte		1			/* line_range */
+	.byte		0x10			/* opcode_base */
+
+	/* Standard lengths */
+	.byte		0
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+
+	/* Include directories */
+	.byte		0
+
+	/* File names */
+	.ascii		"file1.txt\0"
+	.uleb128	0
+	.uleb128	0
+	.uleb128	0
+
+	.byte		0
+
+.Lline1_lines:
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lbegin_func_cu1
+
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	3	/* ... to 4 */
+
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		1	/* DW_LNS_copy (second time as an end-of-prologue marker) */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lend_func_cu1
+
+	.byte		0	/* DW_LNE_end_of_sequence */
+	.uleb128	1
+	.byte		1
+
+.Lline1_end:
+
+/* Abbrev table -- compressed */
+	.section .zdebug_abbrev
+.Labbrev1_begin:
+	.ascii		"ZLIB"
+	.4byte		0
+	.2byte		0
+	.byte		0
+	.byte		51
+	.byte		0x78
+	.byte		0x5e
+	.byte		0x63
+	.byte		0x14
+	.byte		0x64
+	.byte		0x14
+	.byte		0x60
+	.byte		0x13
+	.byte		0x62
+	.byte		0x14
+	.byte		0x64
+	.byte		0x64
+	.byte		0xe6
+	.byte		0x50
+	.byte		0xe5
+	.byte		0x10
+	.byte		0xe6
+	.byte		0x66
+	.byte		0x60
+	.byte		0x60
+	.byte		0xd2
+	.byte		0x63
+	.byte		0xb0
+	.byte		0xe7
+	.byte		0xb1
+	.byte		0xe2
+	.byte		0xb6
+	.byte		0xe6
+	.byte		0x66
+	.byte		0xe6
+	.byte		0xf0
+	.byte		0x14
+	.byte		0x16
+	.byte		0x64
+	.byte		0x14
+	.byte		0x62
+	.byte		0x74
+	.byte		0xe0
+	.byte		0x02
+	.byte		0x00
+	.byte		0x25
+	.byte		0x78
+	.byte		0x02
+	.byte		0x81
+	.byte		0x78
+	.byte		0x9c
+	.byte		0x63
+	.byte		0x60
+	.byte		0x60
+	.byte		0x56
+	.byte		0x61
+	.byte		0x60
+	.byte		0xe6
+	.byte		0xe0
+	.byte		0xe6
+	.byte		0xb6
+	.byte		0xe3
+	.byte		0x66
+	.byte		0x00
+	.byte		0x02
+	.byte		0x00
+	.byte		0x04
+	.byte		0x9c
+	.byte		0x00
+	.byte		0x92
--- /dev/null	2007-10-18 09:27:25.000000000 -0700
+++ gdb/testsuite/gdb.dwarf2/dw2-compressed.exp	2008-04-02 23:32:14.233338000 -0700
@@ -0,0 +1,52 @@
+# Copyright 2008 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Minimal DWARF-2 unit test
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+# For now pick a sampling of likely targets.
+if {![istarget *-*-linux*]
+    && ![istarget *-*-gnu*]
+    && ![istarget *-*-elf*]
+    && ![istarget *-*-openbsd*]
+    && ![istarget arm-*-eabi*]
+    && ![istarget powerpc-*-eabi*]} {
+    return 0  
+}
+
+set testfile "dw2-compressed"
+set srcfile ${testfile}.S
+set binfile ${objdir}/${subdir}/${testfile}.x
+
+if  { [gdb_compile "${srcdir}/${subdir}/main.c" "main-ndebug.o" object -g0] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${testfile}.o" object {nodebug}] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${testfile}.o main-ndebug.o -static -nostdlib" "${binfile}" executable {debug}] != "" } {
+    return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+gdb_test "set listsize 1" ""
+gdb_test "list func_cu1" "4\[ \t\]+File 1 Line 4"
+gdb_test "ptype func_cu1" "type = int \\(\\)"

Re: Patch to handle compressed sections

[Pedro Alves]

A Thursday 03 April 2008 07:43:09, Craig Silverstein wrote:
> I'm sorry to do this, but hot on the heels of my last patch comes a
> new version.  While trying to implement this in gold, I realized that
> gold does not have endianness information handy at the time it's
> writing the compressed header.  

> So I've changed back to writing the 
> uncompressed size always in big-endian.  New patch below.
>

Out of curiosity, did you try running the whole GDB testsuite
outputting compressed debug info?  Perhaps with
"set GDBFLAGS=\"-Wl,--whatever-switch-is-necessary\"" in your
site.exp?

-- 
Pedro Alves

Re: Patch to handle compressed sections

[Pedro Alves]

A Thursday 03 April 2008 11:45:03, Pedro Alves escreveu:
> A Thursday 03 April 2008 07:43:09, Craig Silverstein wrote:
> > I'm sorry to do this, but hot on the heels of my last patch comes a
> > new version.  While trying to implement this in gold, I realized that
> > gold does not have endianness information handy at the time it's
> > writing the compressed header.
> >
> > So I've changed back to writing the
> > uncompressed size always in big-endian.  New patch below.
>
> Out of curiosity, did you try running the whole GDB testsuite
> outputting compressed debug info?  Perhaps with
> "set GDBFLAGS=\"-Wl,--whatever-switch-is-necessary\"" in your
> site.exp?

Urgh!  ENOCOFFE.  Well, you got the idea.  Did you?


-- 
Pedro Alves

Re: Patch to handle compressed sections

[Craig Silverstein]

} Out of curiosity, did you try running the whole GDB testsuite
} outputting compressed debug info?

Hmm, interesting idea.  I thought of it, but the tests I was looking
at all used assembler to generate the debug sections, so it wasn't
feasible.  But I'm guessing other tests use an actual compiler and
linker.  Now that I've got gold outputting the new format (just
submitted to binutils this morning), I can play around with this.  I
don't think it needs to hold up consideration of this patch, though.

craig

Re: Patch to handle compressed sections

[Craig Silverstein]

} Out of curiosity, did you try running the whole GDB testsuite
} outputting compressed debug info?

OK, I had a chance to do this, and results look good -- no new
regressions that I could spot.

craig

Re: Patch to handle compressed sections

[Craig Silverstein]

} hot on the heels of my last patch comes a new version.

Just following up on this.  How does this latest version of the patch
look, for inclusion?  What's the appropriate next step?

(I've reproduced the patch below for your convenience.)

Thanks,
craig

--cut here--

2008-04-02  Craig Silverstein  <csilvers@google.com>

	* configure.ac (AC_SEARCH_LIBS): Add check for zlib.
	* config.in, configure: Regenerate.
	* dwarf2read.c: Include zlib.h if present.
	Modified *_SECTION macros.
	(section_is_p): New.
	(dwarf2_locate_sections): Use section_is_p instead of strcmp
	(dwarf2_resize_section): New.
	to determine whether a given section has a given name.
	(zlib_decompress_section): New.
	(dwarf2_read_section): Read the compressed section if present
	in the binary.

--- gdb/config.in	2008-03-25 15:53:56.000000000 -0700
+++ gdb/config.in	2008-04-02 23:32:12.692343000 -0700
@@ -472,6 +472,9 @@
 /* Define to 1 if you have the `XML_StopParser' function. */
 #undef HAVE_XML_STOPPARSER
 
+/* Define to 1 if you have the <zlib.h> header file. */
+#undef HAVE_ZLIB_H
+
 /* Define to 1 if your system has the _etext variable. */
 #undef HAVE__ETEXT
 
--- gdb/configure	2008-03-25 15:53:56.000000000 -0700
+++ gdb/configure	2008-04-02 23:32:13.274013000 -0700
@@ -6003,6 +6003,560 @@
 fi
 
 
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+echo "$as_me:$LINENO: checking for library containing zlibVersion" >&5
+echo $ECHO_N "checking for library containing zlibVersion... $ECHO_C" >&6
+if test "${ac_cv_search_zlibVersion+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+ac_cv_search_zlibVersion=no
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="none required"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+if test "$ac_cv_search_zlibVersion" = no; then
+  for ac_lib in z; do
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+    cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="-l$ac_lib"
+break
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+  done
+fi
+LIBS=$ac_func_search_save_LIBS
+fi
+echo "$as_me:$LINENO: result: $ac_cv_search_zlibVersion" >&5
+echo "${ECHO_T}$ac_cv_search_zlibVersion" >&6
+if test "$ac_cv_search_zlibVersion" != no; then
+  test "$ac_cv_search_zlibVersion" = "none required" || LIBS="$ac_cv_search_zlibVersion $LIBS"
+
+for ac_header in zlib.h
+do
+as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+else
+  # Is the header compilable?
+echo "$as_me:$LINENO: checking $ac_header usability" >&5
+echo $ECHO_N "checking $ac_header usability... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+$ac_includes_default
+#include <$ac_header>
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_header_compiler=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+ac_header_compiler=no
+fi
+rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_compiler" >&5
+echo "${ECHO_T}$ac_header_compiler" >&6
+
+# Is the header present?
+echo "$as_me:$LINENO: checking $ac_header presence" >&5
+echo $ECHO_N "checking $ac_header presence... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+#include <$ac_header>
+_ACEOF
+if { (eval echo "$as_me:$LINENO: \"$ac_cpp conftest.$ac_ext\"") >&5
+  (eval $ac_cpp conftest.$ac_ext) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } >/dev/null; then
+  if test -s conftest.err; then
+    ac_cpp_err=$ac_c_preproc_warn_flag
+    ac_cpp_err=$ac_cpp_err$ac_c_werror_flag
+  else
+    ac_cpp_err=
+  fi
+else
+  ac_cpp_err=yes
+fi
+if test -z "$ac_cpp_err"; then
+  ac_header_preproc=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+  ac_header_preproc=no
+fi
+rm -f conftest.err conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_preproc" >&5
+echo "${ECHO_T}$ac_header_preproc" >&6
+
+# So?  What about this header?
+case $ac_header_compiler:$ac_header_preproc:$ac_c_preproc_warn_flag in
+  yes:no: )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&5
+echo "$as_me: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the compiler's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the compiler's result" >&2;}
+    ac_header_preproc=yes
+    ;;
+  no:yes:* )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: present but cannot be compiled" >&5
+echo "$as_me: WARNING: $ac_header: present but cannot be compiled" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     check for missing prerequisite headers?" >&5
+echo "$as_me: WARNING: $ac_header:     check for missing prerequisite headers?" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: see the Autoconf documentation" >&5
+echo "$as_me: WARNING: $ac_header: see the Autoconf documentation" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&5
+echo "$as_me: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the preprocessor's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the preprocessor's result" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: in the future, the compiler will take precedence" >&5
+echo "$as_me: WARNING: $ac_header: in the future, the compiler will take precedence" >&2;}
+    (
+      cat <<\_ASBOX
+## ------------------------------------------ ##
+## Report this to the AC_PACKAGE_NAME lists.  ##
+## ------------------------------------------ ##
+_ASBOX
+    ) |
+      sed "s/^/$as_me: WARNING:     /" >&2
+    ;;
+esac
+echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  eval "$as_ac_Header=\$ac_header_preproc"
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+
+fi
+if test `eval echo '${'$as_ac_Header'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_header" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+
+done
+
+fi
+
+
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+echo "$as_me:$LINENO: checking for library containing zlibVersion" >&5
+echo $ECHO_N "checking for library containing zlibVersion... $ECHO_C" >&6
+if test "${ac_cv_search_zlibVersion+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+ac_cv_search_zlibVersion=no
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="none required"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+if test "$ac_cv_search_zlibVersion" = no; then
+  for ac_lib in z; do
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+    cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char zlibVersion ();
+int
+main ()
+{
+zlibVersion ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_search_zlibVersion="-l$ac_lib"
+break
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+  done
+fi
+LIBS=$ac_func_search_save_LIBS
+fi
+echo "$as_me:$LINENO: result: $ac_cv_search_zlibVersion" >&5
+echo "${ECHO_T}$ac_cv_search_zlibVersion" >&6
+if test "$ac_cv_search_zlibVersion" != no; then
+  test "$ac_cv_search_zlibVersion" = "none required" || LIBS="$ac_cv_search_zlibVersion $LIBS"
+
+for ac_header in zlib.h
+do
+as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+else
+  # Is the header compilable?
+echo "$as_me:$LINENO: checking $ac_header usability" >&5
+echo $ECHO_N "checking $ac_header usability... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+$ac_includes_default
+#include <$ac_header>
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"
+			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_header_compiler=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+ac_header_compiler=no
+fi
+rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_compiler" >&5
+echo "${ECHO_T}$ac_header_compiler" >&6
+
+# Is the header present?
+echo "$as_me:$LINENO: checking $ac_header presence" >&5
+echo $ECHO_N "checking $ac_header presence... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+#include <$ac_header>
+_ACEOF
+if { (eval echo "$as_me:$LINENO: \"$ac_cpp conftest.$ac_ext\"") >&5
+  (eval $ac_cpp conftest.$ac_ext) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } >/dev/null; then
+  if test -s conftest.err; then
+    ac_cpp_err=$ac_c_preproc_warn_flag
+    ac_cpp_err=$ac_cpp_err$ac_c_werror_flag
+  else
+    ac_cpp_err=
+  fi
+else
+  ac_cpp_err=yes
+fi
+if test -z "$ac_cpp_err"; then
+  ac_header_preproc=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+  ac_header_preproc=no
+fi
+rm -f conftest.err conftest.$ac_ext
+echo "$as_me:$LINENO: result: $ac_header_preproc" >&5
+echo "${ECHO_T}$ac_header_preproc" >&6
+
+# So?  What about this header?
+case $ac_header_compiler:$ac_header_preproc:$ac_c_preproc_warn_flag in
+  yes:no: )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&5
+echo "$as_me: WARNING: $ac_header: accepted by the compiler, rejected by the preprocessor!" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the compiler's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the compiler's result" >&2;}
+    ac_header_preproc=yes
+    ;;
+  no:yes:* )
+    { echo "$as_me:$LINENO: WARNING: $ac_header: present but cannot be compiled" >&5
+echo "$as_me: WARNING: $ac_header: present but cannot be compiled" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     check for missing prerequisite headers?" >&5
+echo "$as_me: WARNING: $ac_header:     check for missing prerequisite headers?" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: see the Autoconf documentation" >&5
+echo "$as_me: WARNING: $ac_header: see the Autoconf documentation" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&5
+echo "$as_me: WARNING: $ac_header:     section \"Present But Cannot Be Compiled\"" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: proceeding with the preprocessor's result" >&5
+echo "$as_me: WARNING: $ac_header: proceeding with the preprocessor's result" >&2;}
+    { echo "$as_me:$LINENO: WARNING: $ac_header: in the future, the compiler will take precedence" >&5
+echo "$as_me: WARNING: $ac_header: in the future, the compiler will take precedence" >&2;}
+    (
+      cat <<\_ASBOX
+## ------------------------------------------ ##
+## Report this to the AC_PACKAGE_NAME lists.  ##
+## ------------------------------------------ ##
+_ASBOX
+    ) |
+      sed "s/^/$as_me: WARNING:     /" >&2
+    ;;
+esac
+echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  eval "$as_ac_Header=\$ac_header_preproc"
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+
+fi
+if test `eval echo '${'$as_ac_Header'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_header" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+
+done
+
+fi
+
+
 # For the TUI, we need enhanced curses functionality.
 #
 # FIXME: kettenis/20040905: We prefer ncurses over the vendor-supplied
--- gdb/configure.ac	2008-03-25 15:53:56.000000000 -0700
+++ gdb/configure.ac	2008-04-02 23:32:13.718654000 -0700
@@ -394,6 +394,9 @@
 # Some systems (e.g. Solaris) have `socketpair' in libsocket.
 AC_SEARCH_LIBS(socketpair, socket)
 
+# Link in zlib if we can.  This allows us to read compressed debug sections.
+AC_SEARCH_LIBS(zlibVersion, z, [AC_CHECK_HEADERS(zlib.h)])
+
 # For the TUI, we need enhanced curses functionality.
 #
 # FIXME: kettenis/20040905: We prefer ncurses over the vendor-supplied
--- gdb/dwarf2read.c	2008-04-02 22:05:37.000000000 -0700
+++ gdb/dwarf2read.c	2008-04-02 23:38:07.077777000 -0700
@@ -50,6 +50,9 @@
 #include "gdb_string.h"
 #include "gdb_assert.h"
 #include <sys/types.h>
+#ifdef HAVE_ZLIB_H
+#include <zlib.h>
+#endif
 
 /* A note on memory usage for this file.
    
@@ -195,17 +198,20 @@
 
 /* names of the debugging sections */
 
-#define INFO_SECTION     ".debug_info"
-#define ABBREV_SECTION   ".debug_abbrev"
-#define LINE_SECTION     ".debug_line"
-#define PUBNAMES_SECTION ".debug_pubnames"
-#define ARANGES_SECTION  ".debug_aranges"
-#define LOC_SECTION      ".debug_loc"
-#define MACINFO_SECTION  ".debug_macinfo"
-#define STR_SECTION      ".debug_str"
-#define RANGES_SECTION   ".debug_ranges"
-#define FRAME_SECTION    ".debug_frame"
-#define EH_FRAME_SECTION ".eh_frame"
+/* Note that if the debugging section has been compressed, it might
+   have a name like .zdebug_info.  */
+
+#define INFO_SECTION     "debug_info"
+#define ABBREV_SECTION   "debug_abbrev"
+#define LINE_SECTION     "debug_line"
+#define PUBNAMES_SECTION "debug_pubnames"
+#define ARANGES_SECTION  "debug_aranges"
+#define LOC_SECTION      "debug_loc"
+#define MACINFO_SECTION  "debug_macinfo"
+#define STR_SECTION      "debug_str"
+#define RANGES_SECTION   "debug_ranges"
+#define FRAME_SECTION    "debug_frame"
+#define EH_FRAME_SECTION "eh_frame"
 
 /* local data types */
 
@@ -1109,6 +1115,18 @@
   return (dwarf_info_section != NULL && dwarf_abbrev_section != NULL);
 }
 
+/* When loading sections, we can either look for ".<name>", or for
+ * ".z<name>", which indicates a compressed section.  */
+
+static int
+section_is_p(asection *sectp, const char *name)
+{
+  return ((sectp->name[0] == '.'
+           && strcmp (sectp->name + 1, name) == 0)
+          || (sectp->name[0] == '.' && sectp->name[1] == 'z'
+              && strcmp (sectp->name + 2, name) == 0));
+}
+
 /* This function is mapped across the sections and remembers the
    offset and size of each of the debugging sections we are interested
    in.  */
@@ -1116,52 +1134,52 @@
 static void
 dwarf2_locate_sections (bfd *abfd, asection *sectp, void *ignore_ptr)
 {
-  if (strcmp (sectp->name, INFO_SECTION) == 0)
+  if (section_is_p (sectp, INFO_SECTION))
     {
       dwarf2_per_objfile->info_size = bfd_get_section_size (sectp);
       dwarf_info_section = sectp;
     }
-  else if (strcmp (sectp->name, ABBREV_SECTION) == 0)
+  else if (section_is_p (sectp, ABBREV_SECTION))
     {
       dwarf2_per_objfile->abbrev_size = bfd_get_section_size (sectp);
       dwarf_abbrev_section = sectp;
     }
-  else if (strcmp (sectp->name, LINE_SECTION) == 0)
+  else if (section_is_p (sectp, LINE_SECTION))
     {
       dwarf2_per_objfile->line_size = bfd_get_section_size (sectp);
       dwarf_line_section = sectp;
     }
-  else if (strcmp (sectp->name, PUBNAMES_SECTION) == 0)
+  else if (section_is_p (sectp, PUBNAMES_SECTION))
     {
       dwarf2_per_objfile->pubnames_size = bfd_get_section_size (sectp);
       dwarf_pubnames_section = sectp;
     }
-  else if (strcmp (sectp->name, ARANGES_SECTION) == 0)
+  else if (section_is_p (sectp, ARANGES_SECTION))
     {
       dwarf2_per_objfile->aranges_size = bfd_get_section_size (sectp);
       dwarf_aranges_section = sectp;
     }
-  else if (strcmp (sectp->name, LOC_SECTION) == 0)
+  else if (section_is_p (sectp, LOC_SECTION))
     {
       dwarf2_per_objfile->loc_size = bfd_get_section_size (sectp);
       dwarf_loc_section = sectp;
     }
-  else if (strcmp (sectp->name, MACINFO_SECTION) == 0)
+  else if (section_is_p (sectp, MACINFO_SECTION))
     {
       dwarf2_per_objfile->macinfo_size = bfd_get_section_size (sectp);
       dwarf_macinfo_section = sectp;
     }
-  else if (strcmp (sectp->name, STR_SECTION) == 0)
+  else if (section_is_p (sectp, STR_SECTION))
     {
       dwarf2_per_objfile->str_size = bfd_get_section_size (sectp);
       dwarf_str_section = sectp;
     }
-  else if (strcmp (sectp->name, FRAME_SECTION) == 0)
+  else if (section_is_p (sectp, FRAME_SECTION))
     {
       dwarf2_per_objfile->frame_size = bfd_get_section_size (sectp);
       dwarf_frame_section = sectp;
     }
-  else if (strcmp (sectp->name, EH_FRAME_SECTION) == 0)
+  else if (section_is_p (sectp, EH_FRAME_SECTION))
     {
       flagword aflag = bfd_get_section_flags (ignore_abfd, sectp);
       if (aflag & SEC_HAS_CONTENTS)
@@ -1170,7 +1188,7 @@
           dwarf_eh_frame_section = sectp;
         }
     }
-  else if (strcmp (sectp->name, RANGES_SECTION) == 0)
+  else if (section_is_p (sectp, RANGES_SECTION))
     {
       dwarf2_per_objfile->ranges_size = bfd_get_section_size (sectp);
       dwarf_ranges_section = sectp;
@@ -1181,6 +1199,40 @@
     dwarf2_per_objfile->has_section_at_zero = 1;
 }
 
+/* This function is called after decompressing a section, so
+   dwarf2_per_objfile can record its new, uncompressed size.  */
+
+static void
+dwarf2_resize_section (asection *sectp, bfd_size_type new_size)
+{
+  if (section_is_p (sectp, INFO_SECTION))
+    dwarf2_per_objfile->info_size = new_size;
+  else if (section_is_p (sectp, ABBREV_SECTION))
+    dwarf2_per_objfile->abbrev_size = new_size;
+  else if (section_is_p (sectp, LINE_SECTION))
+    dwarf2_per_objfile->line_size = new_size;
+  else if (section_is_p (sectp, PUBNAMES_SECTION))
+    dwarf2_per_objfile->pubnames_size = new_size;
+  else if (section_is_p (sectp, ARANGES_SECTION))
+    dwarf2_per_objfile->aranges_size = new_size;
+  else if (section_is_p (sectp, LOC_SECTION))
+    dwarf2_per_objfile->loc_size = new_size;
+  else if (section_is_p (sectp, MACINFO_SECTION))
+    dwarf2_per_objfile->macinfo_size = new_size;
+  else if (section_is_p (sectp, STR_SECTION))
+    dwarf2_per_objfile->str_size = new_size;
+  else if (section_is_p (sectp, FRAME_SECTION))
+    dwarf2_per_objfile->frame_size = new_size;
+  else if (section_is_p (sectp, EH_FRAME_SECTION))
+    dwarf2_per_objfile->eh_frame_size = new_size;
+  else if (section_is_p (sectp, RANGES_SECTION))
+    dwarf2_per_objfile->ranges_size = new_size;
+  else
+    internal_error (__FILE__, __LINE__,
+		    _("dwarf2_resize_section: missing section_is_p check: %s"),
+                    sectp->name);
+}
+
 /* Build a partial symbol table.  */
 
 void
@@ -5236,8 +5288,87 @@
     }
 }
 
+/* Decompress a section that was compressed using zlib.  Store the
+   decompressed buffer, and its size, in OUTBUF and OUTSIZE.  */
+
+static void
+zlib_decompress_section (struct objfile *objfile, asection *sectp,
+                         gdb_byte **outbuf, bfd_size_type *outsize)
+{
+#ifndef HAVE_ZLIB_H
+  error (_("Support for zlib-compressed DWARF data (from '%s') "
+           "is disabled in this copy of GDB"),
+         bfd_get_filename (abfd));
+#else
+  bfd *abfd = objfile->obfd;
+  bfd_size_type compressed_size = bfd_get_section_size (sectp);
+  gdb_byte *compressed_buffer = xmalloc (compressed_size);
+  bfd_size_type uncompressed_size;
+  gdb_byte *uncompressed_buffer;
+  z_stream strm;
+  int rc;
+  int header_size = 12;
+
+  if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
+      || bfd_bread (compressed_buffer, compressed_size, abfd) != compressed_size)
+    error (_("Dwarf Error: Can't read DWARF data from '%s'"),
+           bfd_get_filename (abfd));
+
+  /* Read the zlib header.  In this case, it should be "ZLIB" followed
+     by the uncompressed section size, 8 bytes in big-endian order.  */
+  if (compressed_size < header_size
+      || strncmp (compressed_buffer, "ZLIB", 4) != 0)
+    error (_("Dwarf Error: Corrupt DWARF ZLIB header from '%s'"),
+           bfd_get_filename (abfd));
+  uncompressed_size = compressed_buffer[4]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[5]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[6]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[7]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[8]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[9]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[10]; uncompressed_size <<= 8;
+  uncompressed_size += compressed_buffer[11];
+
+  /* It is possible the section consists of several compressed
+     buffers concatenated together, so we uncompress in a loop.  */
+  strm.zalloc = NULL;
+  strm.zfree = NULL;
+  strm.opaque = NULL;
+  strm.avail_in = compressed_size - header_size;
+  strm.next_in = (Bytef*) compressed_buffer + header_size;
+  strm.avail_out = uncompressed_size;
+  uncompressed_buffer = obstack_alloc (&objfile->objfile_obstack,
+                                       uncompressed_size);
+  rc = inflateInit (&strm);
+  while (strm.avail_in > 0)
+    {
+      if (rc != Z_OK)
+        error (_("Dwarf Error: setting up DWARF uncompression in '%s': %d"),
+               bfd_get_filename (abfd), rc);
+      strm.next_out = ((Bytef*) uncompressed_buffer
+                       + (uncompressed_size - strm.avail_out));
+      rc = inflate (&strm, Z_FINISH);
+      if (rc != Z_STREAM_END)
+        error (_("Dwarf Error: zlib error uncompressing from '%s': %d"),
+               bfd_get_filename (abfd), rc);
+      rc = inflateReset (&strm);
+    }
+  rc = inflateEnd (&strm);
+  if (rc != Z_OK
+      || strm.avail_out != 0)
+    error (_("Dwarf Error: concluding DWARF uncompression in '%s': %d"),
+           bfd_get_filename (abfd), rc);
+
+  xfree (compressed_buffer);
+  *outbuf = uncompressed_buffer;
+  *outsize = uncompressed_size;
+#endif
+}
+
+
 /* Read the contents of the section at OFFSET and of size SIZE from the
-   object file specified by OBJFILE into the objfile_obstack and return it.  */
+   object file specified by OBJFILE into the objfile_obstack and return it.
+   If the section is compressed, uncompress it before returning.  */
 
 gdb_byte *
 dwarf2_read_section (struct objfile *objfile, asection *sectp)
@@ -5245,11 +5376,31 @@
   bfd *abfd = objfile->obfd;
   gdb_byte *buf, *retbuf;
   bfd_size_type size = bfd_get_section_size (sectp);
+  unsigned char header[4];
 
   if (size == 0)
     return NULL;
 
+  /* Check if the file has a 4-byte header indicating compression.  */
+  if (size > sizeof (header)
+      && bfd_seek (abfd, sectp->filepos, SEEK_SET) == 0
+      && bfd_bread (header, sizeof (header), abfd) == sizeof (header))
+    {
+      /* Upon decompression, update the buffer and its size.  */
+      if (strncmp (header, "ZLIB", sizeof (header)) == 0)
+        {
+          zlib_decompress_section (objfile, sectp, &buf, &size);
+          dwarf2_resize_section (sectp, size);
+          return buf;
+        }
+    }
+
+  /* If we get here, we are a normal, not-compressed section.  */
   buf = obstack_alloc (&objfile->objfile_obstack, size);
+  /* When debugging .o files, we may need to apply relocations; see
+     http://www.cygwin.com/ml/gdb-patches/2002-04/msg00136.html .
+     We never compress sections in .o files, so we only need to
+     try this when the section is not compressed.  */
   retbuf = symfile_relocate_debug_section (abfd, sectp, buf);
   if (retbuf != NULL)
     return retbuf;
--- /dev/null	2007-10-18 09:27:25.000000000 -0700
+++ gdb/testsuite/gdb.dwarf2/dw2-compressed.S	2008-04-02 23:39:04.480179000 -0700
@@ -0,0 +1,218 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2008 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* This tests that gdb can read compressed sections.  The contents
+   are the same as dw2-basic.S, but the .debug_abbrev section has been
+   comrpessed using zlib.  */
+
+/* Dummy function to provide debug information for.  */
+
+	.text
+	.globl _start
+_start:
+	.int 0
+.Lbegin_text1:
+	.globl func_cu1
+	.type func_cu1, %function
+func_cu1:
+.Lbegin_func_cu1:
+	.int 0
+.Lend_func_cu1:
+	.size func_cu1, .-func_cu1
+.Lend_text1:
+
+/* Debug information */
+
+	.section .debug_info
+.Lcu1_begin:
+	/* CU header */
+	.4byte	.Lcu1_end - .Lcu1_start		/* Length of Compilation Unit */
+.Lcu1_start:
+	.2byte	2				/* DWARF Version */
+	.4byte	.Labbrev1_begin			/* Offset into abbrev section */
+	.byte	4				/* Pointer size */
+
+	/* CU die */
+	.uleb128 1				/* Abbrev: DW_TAG_compile_unit */
+	.4byte	.Lline1_begin			/* DW_AT_stmt_list */
+	.4byte	.Lend_text1			/* DW_AT_high_pc */
+	.4byte	.Lbegin_text1			/* DW_AT_low_pc */
+	.ascii	"file1.txt\0"			/* DW_AT_name */
+	.ascii	"GNU C 3.3.3\0"			/* DW_AT_producer */
+	.byte	1				/* DW_AT_language (C) */
+
+	/* func_cu1 */
+	.uleb128	2			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.byte		1			/* DW_AT_decl_file */
+	.byte		2			/* DW_AT_decl_line */
+	.ascii		"func_cu1\0"		/* DW_AT_name */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+	.4byte		.Lbegin_func_cu1	/* DW_AT_low_pc */
+	.4byte		.Lend_func_cu1		/* DW_AT_high_pc */
+	.byte		1			/* DW_AT_frame_base: length */
+	.byte		0x55			/* DW_AT_frame_base: DW_OP_reg5 */
+
+.Ltype_int:
+	.uleb128	3			/* Abbrev: DW_TAG_base_type */
+	.ascii		"int\0"			/* DW_AT_name */
+	.byte		4			/* DW_AT_byte_size */
+	.byte		5			/* DW_AT_encoding */
+
+	.byte		0			/* End of children of CU */
+
+.Lcu1_end:
+
+/* Line table */
+	.section .debug_line
+.Lline1_begin:
+	.4byte		.Lline1_end - .Lline1_start	/* Initial length */
+.Lline1_start:
+	.2byte		2			/* Version */
+	.4byte		.Lline1_lines - .Lline1_hdr	/* header_length */
+.Lline1_hdr:
+	.byte		1			/* Minimum insn length */
+	.byte		1			/* default_is_stmt */
+	.byte		1			/* line_base */
+ 	.byte		1			/* line_range */
+	.byte		0x10			/* opcode_base */
+
+	/* Standard lengths */
+	.byte		0
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+
+	/* Include directories */
+	.byte		0
+
+	/* File names */
+	.ascii		"file1.txt\0"
+	.uleb128	0
+	.uleb128	0
+	.uleb128	0
+
+	.byte		0
+
+.Lline1_lines:
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lbegin_func_cu1
+
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	3	/* ... to 4 */
+
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		1	/* DW_LNS_copy (second time as an end-of-prologue marker) */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lend_func_cu1
+
+	.byte		0	/* DW_LNE_end_of_sequence */
+	.uleb128	1
+	.byte		1
+
+.Lline1_end:
+
+/* Abbrev table -- compressed */
+	.section .zdebug_abbrev
+.Labbrev1_begin:
+	.ascii		"ZLIB"
+	.4byte		0
+	.2byte		0
+	.byte		0
+	.byte		51
+	.byte		0x78
+	.byte		0x5e
+	.byte		0x63
+	.byte		0x14
+	.byte		0x64
+	.byte		0x14
+	.byte		0x60
+	.byte		0x13
+	.byte		0x62
+	.byte		0x14
+	.byte		0x64
+	.byte		0x64
+	.byte		0xe6
+	.byte		0x50
+	.byte		0xe5
+	.byte		0x10
+	.byte		0xe6
+	.byte		0x66
+	.byte		0x60
+	.byte		0x60
+	.byte		0xd2
+	.byte		0x63
+	.byte		0xb0
+	.byte		0xe7
+	.byte		0xb1
+	.byte		0xe2
+	.byte		0xb6
+	.byte		0xe6
+	.byte		0x66
+	.byte		0xe6
+	.byte		0xf0
+	.byte		0x14
+	.byte		0x16
+	.byte		0x64
+	.byte		0x14
+	.byte		0x62
+	.byte		0x74
+	.byte		0xe0
+	.byte		0x02
+	.byte		0x00
+	.byte		0x25
+	.byte		0x78
+	.byte		0x02
+	.byte		0x81
+	.byte		0x78
+	.byte		0x9c
+	.byte		0x63
+	.byte		0x60
+	.byte		0x60
+	.byte		0x56
+	.byte		0x61
+	.byte		0x60
+	.byte		0xe6
+	.byte		0xe0
+	.byte		0xe6
+	.byte		0xb6
+	.byte		0xe3
+	.byte		0x66
+	.byte		0x00
+	.byte		0x02
+	.byte		0x00
+	.byte		0x04
+	.byte		0x9c
+	.byte		0x00
+	.byte		0x92
--- /dev/null	2007-10-18 09:27:25.000000000 -0700
+++ gdb/testsuite/gdb.dwarf2/dw2-compressed.exp	2008-04-02 23:32:14.233338000 -0700
@@ -0,0 +1,52 @@
+# Copyright 2008 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Minimal DWARF-2 unit test
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+# For now pick a sampling of likely targets.
+if {![istarget *-*-linux*]
+    && ![istarget *-*-gnu*]
+    && ![istarget *-*-elf*]
+    && ![istarget *-*-openbsd*]
+    && ![istarget arm-*-eabi*]
+    && ![istarget powerpc-*-eabi*]} {
+    return 0  
+}
+
+set testfile "dw2-compressed"
+set srcfile ${testfile}.S
+set binfile ${objdir}/${subdir}/${testfile}.x
+
+if  { [gdb_compile "${srcdir}/${subdir}/main.c" "main-ndebug.o" object -g0] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${testfile}.o" object {nodebug}] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${testfile}.o main-ndebug.o -static -nostdlib" "${binfile}" executable {debug}] != "" } {
+    return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+gdb_test "set listsize 1" ""
+gdb_test "list func_cu1" "4\[ \t\]+File 1 Line 4"
+gdb_test "ptype func_cu1" "type = int \\(\\)"

Re: Patch to handle compressed sections

[Daniel Jacobowitz]

Just a general comment - I've been seeing a lot of gold patches
lately where gold doesn't have a certain piece of data available at a
certain point... that seems like a really underwhelming reason to
use a big endian size in an otherwise little endian file.  But
as I said earlier, the choice of header format is pretty arbitrary,
and anyone prepared to read DWARF ought to be able to cope with a
simple big endian integer!  So that's fine.

On Mon, Apr 14, 2008 at 04:45:59PM -0700, Craig Silverstein wrote:
> +/* When loading sections, we can either look for ".<name>", or for
> + * ".z<name>", which indicates a compressed section.  */
> +
> +static int
> +section_is_p(asection *sectp, const char *name)

Space before parenthesis.

> +  /* Read the zlib header.  In this case, it should be "ZLIB" followed
> +     by the uncompressed section size, 8 bytes in big-endian order.  */
> +  if (compressed_size < header_size
> +      || strncmp (compressed_buffer, "ZLIB", 4) != 0)
> +    error (_("Dwarf Error: Corrupt DWARF ZLIB header from '%s'"),
> +           bfd_get_filename (abfd));
> +  uncompressed_size = compressed_buffer[4]; uncompressed_size <<= 8;
> +  uncompressed_size += compressed_buffer[5]; uncompressed_size <<= 8;
> +  uncompressed_size += compressed_buffer[6]; uncompressed_size <<= 8;
> +  uncompressed_size += compressed_buffer[7]; uncompressed_size <<= 8;
> +  uncompressed_size += compressed_buffer[8]; uncompressed_size <<= 8;
> +  uncompressed_size += compressed_buffer[9]; uncompressed_size <<= 8;
> +  uncompressed_size += compressed_buffer[10]; uncompressed_size <<= 8;
> +  uncompressed_size += compressed_buffer[11];

You can use bfd_getb64.

>    buf = obstack_alloc (&objfile->objfile_obstack, size);
> +  /* When debugging .o files, we may need to apply relocations; see
> +     http://www.cygwin.com/ml/gdb-patches/2002-04/msg00136.html .
> +     We never compress sections in .o files, so we only need to
> +     try this when the section is not compressed.  */

Use the sourceware.org URL instead, please.  Actually, it'd make me
happy if you couldn't get at these archives via cygwin.com.  It
confuses search results...

Aside from that, this is fine to commit.  Do you have write access?
If not, request it using the sourceware form - if you have write
access to binutils then you already do.  Then add yourself to write
after approval in MAINTAINERS and check in the final patch.

The other things needed for this feature are, IMO:

  - A NEWS entry.
  - An entry in the manual.  I'm not sure where, but the format
    of the sections should probably be described in the GDB manual
    somewhere.
  - An addition to the "Requirements" section of the GDB manual,
    explaining why you should have zlib.

Could you follow up with those, please?  The other thing I very
much want is an objcopy option to compress DWARF sections, but
that's clearly beyond the call of duty.  That will let GNU ld
users take advantage of this and is probably easier than teaching GNU
ld to compress .debug_info (though that would be nice, too).

Other tools that would benefit from reading such sections include
readelf and addr2line (bfd/dwarf2.c).

-- 
Daniel Jacobowitz
CodeSourcery

Re: Patch to handle compressed sections

[Craig Silverstein]

} Space before parenthesis.

Doh, and I was so careful looking for all of those!

} You can use bfd_getb64.

Yeah, we had some debate about that internally.  The issue is that
bfd_getb64 crashes on machines without a 64-bit int type.  That seemed
unnecessarily harsh here, especially since in practice section sizes
will never be longer than 32 bits.

Do you feel that strongly about it?  I'd be more comfortable with code
that didn't make 32-bit assumptions.  I can comment it if that will
help.

} Use the sourceware.org URL instead, please.

Sure thing.

} Do you have write access?  If not, request it using the sourceware
} form - if you have write access to binutils then you already do.

I don't have write access.  I've requested it.

} The other things needed for this feature are, IMO:

Makes sense to me.  Should that be part of this patch, or is it ok to
do it in a followup patch?

} The other thing I very much want is an objcopy option to compress
} DWARF sections, but that's clearly beyond the call of duty.  That
} will let GNU ld users take advantage of this and is probably easier
} than teaching GNU ld to compress .debug_info (though that would be
} nice, too).

Makes sense.  Further plans, if we ever get around to it, include
adding support to readelf, objdump, and addr2line, and adding support
to as to generate compressed sections in .o files (obviously, this
will require a linker that knows how to deal with that, so it's a
longer-term plan).  I'll add objcopy to the list.

craig

Re: Patch to handle compressed sections

[Daniel Jacobowitz]

On Thu, Apr 17, 2008 at 11:57:52AM -0700, Craig Silverstein wrote:
> } You can use bfd_getb64.
> 
> Yeah, we had some debate about that internally.  The issue is that
> bfd_getb64 crashes on machines without a 64-bit int type.  That seemed
> unnecessarily harsh here, especially since in practice section sizes
> will never be longer than 32 bits.

I see.  Well, you could use bfd_getb32 twice... I just felt that the
eight copies of that line were excessive.

> } The other things needed for this feature are, IMO:
> 
> Makes sense to me.  Should that be part of this patch, or is it ok to
> do it in a followup patch?

A followup is fine, as long as I know you're going to look at it :-)

> Makes sense.  Further plans, if we ever get around to it, include
> adding support to readelf, objdump, and addr2line, and adding support
> to as to generate compressed sections in .o files (obviously, this
> will require a linker that knows how to deal with that, so it's a
> longer-term plan).  I'll add objcopy to the list.

Thanks!  I may get around to these too - there's been an outstanding
request for this in Debian for years.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Patch to handle compressed sections

[Daniel Jacobowitz]

On Fri, Apr 18, 2008 at 02:28:06PM -0700, Craig Silverstein wrote:
> } I see.  Well, you could use bfd_getb32 twice... I just felt that the
> } eight copies of that line were excessive.
> 
> Then you'd do something like
>    size = (a << 32) + b;
> which likewise won't work well (well, will give a compiler warning) on
> 32-bit systems.

Not on 32-bit systems, on systems without a 64-bit type.  I don't know
if that even describes any system GDB still compiles on.

> I agree the code ends up being verbose, but it's pretty
> straightforward and robust.  Would you be ok with the code going in
> the way it is now?

Robust is not the word I'd use, since it'll silently drop bits if
the section is in fact monstrously huge.  Of course, if you had such a
file and tried to open it on a system without a 64-bit type, this
seems like the least thing that would go wrong.

I've no objection to the current version.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Patch to handle compressed sections

[Daniel Jacobowitz]

On Fri, Apr 18, 2008 at 02:28:06PM -0700, Craig Silverstein wrote:
> } I see.  Well, you could use bfd_getb32 twice... I just felt that the
> } eight copies of that line were excessive.
> 
> Then you'd do something like
>    size = (a << 32) + b;
> which likewise won't work well (well, will give a compiler warning) on
> 32-bit systems.

Not on 32-bit systems, on systems without a 64-bit type.  I don't know
if that even describes any system GDB still compiles on.

> I agree the code ends up being verbose, but it's pretty
> straightforward and robust.  Would you be ok with the code going in
> the way it is now?

Robust is not the word I'd use, since it'll silently drop bits if
the section is in fact monstrously huge.  Of course, if you had such a
file and tried to open it on a system without a 64-bit type, this
seems like the least thing that would go wrong.

I've no objection to the current version.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Patch to handle compressed sections

[Craig Silverstein]

} I see.  Well, you could use bfd_getb32 twice... I just felt that the
} eight copies of that line were excessive.

Then you'd do something like
   size = (a << 32) + b;
which likewise won't work well (well, will give a compiler warning) on
32-bit systems.

I agree the code ends up being verbose, but it's pretty
straightforward and robust.  Would you be ok with the code going in
the way it is now?

craig