[patch] Fix gdb crash on some missing ELF debug info

[Jan Kratochvil <lace@jankratochvil.net>]

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Hi,

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196439

On Fedora Core 5:
	gdb /usr/lib/valgrind/x86-linux/memcheck
	break _start_in_C
	run
segfaults as the file's debug info references location list while no
".debug_loc" section exists there.
	eu-readelf -w /usr/lib/valgrind/x86-linux/memcheck
		DWARF section '.debug_info' at offset 0x14759c:
		...
		 [ 176d4]    subprogram
		...
		             name		  "_start_in_C"
		...
		             frame_base 	  location list [ 116d7]

Trivia complaint on the file coherency, no frame_info debugging available for
such functions.


Regards,
Jan Kratochvil

[-- Attachment #2: gdb-cvs20060623-debug_loc.patch --]
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https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196439

Fedora Core 5:
	gdb /usr/lib/valgrind/x86-linux/memcheck
	break _start_in_C
	run
segfault

eu-readelf -w /usr/lib/valgrind/x86-linux/memcheck
	DWARF section '.debug_info' at offset 0x14759c:
	...
	 [ 176d4]    subprogram
	...
	             name                 "_start_in_C"
	...
	             frame_base           location list [ 116d7]
corrupted as no location lists (.debug_loc) exist there at all.


Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.199
diff -u -p -r1.199 dwarf2read.c
--- dwarf2read.c	14 Jun 2006 15:06:35 -0000	1.199
+++ dwarf2read.c	23 Jun 2006 10:28:44 -0000
@@ -9324,7 +9324,9 @@ static void
 dwarf2_symbol_mark_computed (struct attribute *attr, struct symbol *sym,
 			     struct dwarf2_cu *cu)
 {
-  if (attr->form == DW_FORM_data4 || attr->form == DW_FORM_data8)
+  if ((attr->form == DW_FORM_data4 || attr->form == DW_FORM_data8)
+      /* DW_UNSND (attr) != 0 would produce non-zero bogus ->size & ->data */
+      && dwarf2_per_objfile->loc_size)
     {
       struct dwarf2_loclist_baton *baton;