Re: Crash regression for gdb.dwarf2/dw2-inheritance.exp [Re: [RFA 3/3] Initial Fission support, the actual Fission stuff]

[Doug Evans <dje@google.com>]

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On Sun, Apr 29, 2012 at 1:57 AM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
> On Wed, 18 Apr 2012 20:57:38 +0200, Doug Evans wrote:
>> 2012-04-18  Doug Evans  <dje@google.com>
>>
>>       Initial support for Fission.  http://gcc.gnu.org/wiki/DebugFission
>
>  Running gdb/testsuite/gdb.dwarf2/dw2-inheritance.exp ...
> -PASS: gdb.dwarf2/dw2-inheritance.exp: ptype inherited
> +ERROR: couldn't load /unsafegdb/testsuite.unix.-m32/gdb.dwarf2/dw2-inheritance.x into /unsafegdb/testsuite.unix.-m32/../../gdb/gdb (end of file).
> +ERROR: Couldn't send ptype inherited to GDB.
> +UNRESOLVED: gdb.dwarf2/dw2-inheritance.exp: ptype inherited
>
> Program terminated with signal 11, Segmentation fault.
> #0  0x000000000063037c in dwarf_decode_line_header (offset=0, cu=0x2c4b410) at dwarf2read.c:12320
> 12320     abfd = section->asection->owner;
> (gdb) p section->asection
> $2 = (asection *) 0x0
> (gdb) bt
> #0  0x000000000063037c in dwarf_decode_line_header (offset=0, cu=0x2c4b410) at dwarf2read.c:12320
> #1  0x000000000061c354 in dwarf2_build_include_psymtabs (cu=0x2c4b410, die=0x2c4b5d0, pst=0x2c2d810) at dwarf2read.c:3324
> #2  0x000000000061e46b in process_psymtab_comp_unit_reader (reader=0x7fff3fa1ac90, info_ptr=0x2c2d777 "\003base", comp_unit_die=0x2c4b5d0, has_children=1,
>    data=0x0) at dwarf2read.c:4159
> #3  0x000000000061dc53 in init_and_read_dies_worker (this_cu=0x2c2d7a0, use_existing_cu=0, keep=0, die_reader_func=
>    0x61e036 <process_psymtab_comp_unit_reader>, data=0x0) at dwarf2read.c:3895
> #4  0x000000000061dd12 in init_cu_and_read_dies (this_cu=0x2c2d7a0, use_existing_cu=0, keep=0, die_reader_func=0x61e036 <process_psymtab_comp_unit_reader>,
>    data=0x0) at dwarf2read.c:3936
> #5  0x000000000061e4f9 in process_psymtab_comp_unit (this_cu=0x2c2d7a0) at dwarf2read.c:4178
> #6  0x000000000061e726 in dwarf2_build_psymtabs_hard (objfile=0x2c386d0) at dwarf2read.c:4269
> #7  0x000000000061bca2 in dwarf2_build_psymtabs (objfile=0x2c386d0) at dwarf2read.c:3133
> #8  0x0000000000508db2 in read_psyms (objfile=0x2c386d0) at elfread.c:1449
> #9  0x000000000058f9be in require_partial_symbols (objfile=0x2c386d0, verbose=0) at psymtab.c:92
>
> It happens on RHEL-6 i386/x86_68/x86_64-m32.  Feel free to request more info.
>
>
> Regards,
> Jan

Hi.
I can't recreate this on my fc16 box (neither i386 nor amd64), but the
it's easy enough to see what the issue is.

Can you test this patch?  Regression tested here.
It also fixes a potential segv in dwarf_decode_macros.

2012-04-29  Doug Evans  <dje@seba.sebabeach.org>

        * dwarf2read.c (dwarf_decode_macros): New arg section_name.
        All callers updated.
        (init_cu_die_reader): Verify the section is non-empty.
        (dwarf_decode_line_header): Don't dereference section->asection
        until we know the section is present.  Return NULL, not 0.

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2012-04-29  Doug Evans  <dje@seba.sebabeach.org>

	* dwarf2read.c (dwarf_decode_macros): New arg section_name.
	All callers updated.
	(init_cu_die_reader): Verify the section is non-empty.
	(dwarf_decode_line_header): Don't dereference section->asection
	until we know the section is present.  Return NULL, not 0.

Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.644
diff -u -p -r1.644 dwarf2read.c
--- dwarf2read.c	28 Apr 2012 23:22:13 -0000	1.644
+++ dwarf2read.c	29 Apr 2012 22:13:16 -0000
@@ -1317,7 +1317,7 @@ static struct die_info *dwarf_alloc_die 
 static void dwarf_decode_macros (struct line_header *, unsigned int,
                                  char *, bfd *, struct dwarf2_cu *,
 				 struct dwarf2_section_info *,
-				 int);
+				 int, const char *);
 
 static int attr_form_is_block (struct attribute *);
 
@@ -1671,7 +1671,8 @@ zlib_decompress_section (struct objfile 
 #endif
 }
 
-/* A helper function that decides whether a section is empty.  */
+/* A helper function that decides whether a section is empty,
+   or not present.  */
 
 static int
 dwarf2_section_empty_p (struct dwarf2_section_info *info)
@@ -3588,7 +3589,7 @@ init_cu_die_reader (struct die_reader_sp
 		    struct dwarf2_section_info *section,
 		    struct dwo_file *dwo_file)
 {
-  gdb_assert (section->readin);
+  gdb_assert (section->readin && section->buffer != NULL);
   reader->abfd = section->asection->owner;
   reader->cu = cu;
   reader->dwo_file = dwo_file;
@@ -6354,7 +6355,8 @@ read_file_scope (struct die_info *die, s
 
       dwarf_decode_macros (cu->line_header, DW_UNSND (attr),
 			   comp_dir, abfd, cu,
-			   &dwarf2_per_objfile->macro, 1);
+			   &dwarf2_per_objfile->macro, 1,
+			   ".debug_macro");
     }
   else
     {
@@ -6365,7 +6367,8 @@ read_file_scope (struct die_info *die, s
 
 	  dwarf_decode_macros (cu->line_header, macro_offset,
 			       comp_dir, abfd, cu,
-			       &dwarf2_per_objfile->macinfo, 0);
+			       &dwarf2_per_objfile->macinfo, 0,
+			       ".debug_macinfo");
 	}
     }
 
@@ -12317,7 +12320,6 @@ dwarf_decode_line_header (unsigned int o
     section = &cu->dwo_unit->dwo_file->sections.line;
   else
     section = &dwarf2_per_objfile->line;
-  abfd = section->asection->owner;
 
   dwarf2_read_section (dwarf2_per_objfile->objfile, section);
   if (section->buffer == NULL)
@@ -12329,6 +12331,10 @@ dwarf_decode_line_header (unsigned int o
       return 0;
     }
 
+  /* We can't do this until we know the section is non-empty.
+     Only then do we know we have such a section.  */
+  abfd = section->asection->owner;
+
   /* Make sure that at least there's room for the total_length field.
      That could be 12 bytes long, but we're just going to fudge that.  */
   if (offset + 4 >= section->size)
@@ -16894,7 +16900,7 @@ dwarf_decode_macros (struct line_header 
                      char *comp_dir, bfd *abfd,
                      struct dwarf2_cu *cu,
 		     struct dwarf2_section_info *section,
-		     int section_is_gnu)
+		     int section_is_gnu, const char *section_name)
 {
   struct objfile *objfile = dwarf2_per_objfile->objfile;
   gdb_byte *mac_ptr, *mac_end;
@@ -16909,8 +16915,7 @@ dwarf_decode_macros (struct line_header 
   dwarf2_read_section (objfile, section);
   if (section->buffer == NULL)
     {
-      complaint (&symfile_complaints, _("missing %s section"),
-		 section->asection->name);
+      complaint (&symfile_complaints, _("missing %s section"), section_name);
       return;
     }