6.0 BRANCH PATCH: fix dbxread handling of variables' section offsets

[Jim Blandy <jimb@redhat.com>]

This patch is smaller than the ChangeLog entries would suggest.

2003-09-19  Jim Blandy  <jimb@redhat.com>

	Merge from mainline:
	
	2003-09-12  Jim Blandy  <jimb@redhat.com>

	* dbxread.c (read_dbx_symtab): Don't report an internal error if
	the file has no .data, .bss, or .rodata sections.  Instead wait
	until we see a variable alleged to live in one of those sections.

	2003-09-12  Jim Blandy  <jimb@redhat.com>

	* dbxread.c (read_dbx_symtab): If we have no .data section and no
	.bss section, presume that any variables we find live in the
	.rodata section.

	2003-09-12  Jim Blandy  <jimb@redhat.com>

	* dbxread.c (read_dbx_symtab): Add FIXME about finding section
	offsets for global and static variables.

	2003-09-09  Jim Blandy  <jimb@redhat.com>

	* dbxread.c (read_dbx_symtab): The N_DATA and N_DATA | N_EXT
	symbol types are, by definition, in the .data section, so it is
	correct to use SECT_OFF_DATA (objfile) here, not data_sect_index.
	If there is no .data section, there should be no N_DATA or N_DATA
	| N_EXT symbols.

	2003-07-10  Jim Blandy  <jimb@redhat.com>

	* Makefile.in (dbxread.o): Note new dependency on $(gdb_assert_h).
	* dbxread.c: #include "gdb_assert.h".
	(read_dbx_symtab): If the objfile has no .data section, use the
	section index for the .bss section instead.

Index: gdb/Makefile.in
===================================================================
RCS file: /cvs/src/src/gdb/Makefile.in,v
retrieving revision 1.410.2.14
diff -c -r1.410.2.14 Makefile.in
*** gdb/Makefile.in	18 Aug 2003 18:10:52 -0000	1.410.2.14
--- gdb/Makefile.in	20 Sep 2003 00:12:18 -0000
***************
*** 1663,1669 ****
  	$(gdb_stat_h) $(symtab_h) $(breakpoint_h) $(target_h) $(gdbcore_h) \
  	$(libaout_h) $(symfile_h) $(objfiles_h) $(buildsym_h) $(stabsread_h) \
  	$(gdb_stabs_h) $(demangle_h) $(language_h) $(complaints_h) \
! 	$(cp_abi_h) $(aout_aout64_h) $(aout_stab_gnu_h)
  dcache.o: dcache.c $(defs_h) $(dcache_h) $(gdbcmd_h) $(gdb_string_h) \
  	$(gdbcore_h) $(target_h)
  delta68-nat.o: delta68-nat.c $(defs_h)
--- 1663,1669 ----
  	$(gdb_stat_h) $(symtab_h) $(breakpoint_h) $(target_h) $(gdbcore_h) \
  	$(libaout_h) $(symfile_h) $(objfiles_h) $(buildsym_h) $(stabsread_h) \
  	$(gdb_stabs_h) $(demangle_h) $(language_h) $(complaints_h) \
! 	$(cp_abi_h) $(aout_aout64_h) $(aout_stab_gnu_h) $(gdb_assert_h)
  dcache.o: dcache.c $(defs_h) $(dcache_h) $(gdbcmd_h) $(gdb_string_h) \
  	$(gdbcore_h) $(target_h)
  delta68-nat.o: delta68-nat.c $(defs_h)
Index: gdb/dbxread.c
===================================================================
RCS file: /cvs/src/src/gdb/dbxread.c,v
retrieving revision 1.48
diff -c -r1.48 dbxread.c
*** gdb/dbxread.c	11 Jun 2003 22:27:10 -0000	1.48
--- gdb/dbxread.c	20 Sep 2003 00:12:20 -0000
***************
*** 58,63 ****
--- 58,64 ----
  #include "language.h"		/* Needed for local_hex_string */
  #include "complaints.h"
  #include "cp-abi.h"
+ #include "gdb_assert.h"
  
  #include "aout/aout64.h"
  #include "aout/stab_gnu.h"	/* We always use GNU stabs, not native, now */
***************
*** 1304,1309 ****
--- 1305,1311 ----
    struct cleanup *back_to;
    bfd *abfd;
    int textlow_not_set;
+   int data_sect_index;
  
    /* Current partial symtab */
    struct partial_symtab *pst;
***************
*** 1355,1360 ****
--- 1357,1394 ----
    textlow_not_set = 1;
    has_line_numbers = 0;
  
+   /* FIXME: jimb/2003-09-12: We don't apply the right section's offset
+      to global and static variables.  The stab for a global or static
+      variable doesn't give us any indication of which section it's in,
+      so we can't tell immediately which offset in
+      objfile->section_offsets we should apply to the variable's
+      address.
+ 
+      We could certainly find out which section contains the variable
+      by looking up the variable's unrelocated address with
+      find_pc_section, but that would be expensive; this is the
+      function that constructs the partial symbol tables by examining
+      every symbol in the entire executable, and it's
+      performance-critical.  So that expense would not be welcome.  I'm
+      not sure what to do about this at the moment.
+ 
+      What we have done for years is to simply assume that the .data
+      section's offset is appropriate for all global and static
+      variables.  Recently, this was expanded to fall back to the .bss
+      section's offset if there is no .data section, and then to the
+      .rodata section's offset.  */
+   data_sect_index = objfile->sect_index_data;
+   if (data_sect_index == -1)
+     data_sect_index = SECT_OFF_BSS (objfile);
+   if (data_sect_index == -1)
+     data_sect_index = SECT_OFF_RODATA (objfile);
+ 
+   /* If data_sect_index is still -1, that's okay.  It's perfectly fine
+      for the file to have no .data, no .bss, and no .text at all, if
+      it also has no global or static variables.  If it does, we will
+      get an internal error from an ANOFFSET macro below when we try to
+      use data_sect_index.  */
+ 
    for (symnum = 0; symnum < DBX_SYMCOUNT (objfile); symnum++)
      {
        /* Get the symbol for this run and pull out some info */
***************
*** 1757,1763 ****
  	  switch (p[1])
  	  {
  	  case 'S':
! 	    nlist.n_value += ANOFFSET (objfile->section_offsets, SECT_OFF_DATA (objfile));
  #ifdef STATIC_TRANSFORM_NAME
  	    namestring = STATIC_TRANSFORM_NAME (namestring);
  #endif
--- 1791,1797 ----
  	  switch (p[1])
  	  {
  	  case 'S':
! 	    nlist.n_value += ANOFFSET (objfile->section_offsets, data_sect_index);
  #ifdef STATIC_TRANSFORM_NAME
  	    namestring = STATIC_TRANSFORM_NAME (namestring);
  #endif
***************
*** 1768,1774 ****
  				 psymtab_language, objfile);
  	    continue;
  	  case 'G':
! 	    nlist.n_value += ANOFFSET (objfile->section_offsets, SECT_OFF_DATA (objfile));
  	    /* The addresses in these entries are reported to be
  	       wrong.  See the code that reads 'G's for symtabs. */
  	    add_psymbol_to_list (namestring, p - namestring,
--- 1802,1808 ----
  				 psymtab_language, objfile);
  	    continue;
  	  case 'G':
! 	    nlist.n_value += ANOFFSET (objfile->section_offsets, data_sect_index);
  	    /* The addresses in these entries are reported to be
  	       wrong.  See the code that reads 'G's for symtabs. */
  	    add_psymbol_to_list (namestring, p - namestring,