[Bug symtab/29367] [gdb, debug-types, gdb-index] Bad CU index complaint not triggered

["vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29367

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom de Vries from comment #0)
> Now the question: is this change correct?
> 
> I can't figure out how a type in a .debug_types section would be addressed
> from the index.
> 
> Maybe 56 is the correct way to address TU 0 ?

At https://sourceware.org/gdb/onlinedocs/gdb/Index-Section-Format.html I find:
...
Note that if there are type CUs, then conceptually CUs and type CUs form a
single list for the purposes of CU indices.
...

I guess that answers my question.

So this:
...
       /* Don't crash on bad data.  */
-      if (cu_index >= per_objfile->per_bfd->all_comp_units.size (CUTU))
+      if (cu_index >= per_objfile->per_bfd->all_comp_units.size (CU))
...
is incorrect, the current code is in fact correct.

But we might be able to be more strict though:
...
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index bcd01107377..8d216318c13 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -2975,7 +2975,13 @@ dw2_symtab_iter_next (struct dw2_symtab_iterator *iter,
                         && symbol_kind != GDB_INDEX_SYMBOL_KIND_NONE);

       /* Don't crash on bad data.  */
-      if (cu_index >= per_objfile->per_bfd->all_comp_units.size ())
+      size_t nr_tus = per_objfile->per_bfd->tu_stats.nr_tus;
+      size_t nr_cus = (per_objfile->per_bfd->all_comp_units.size () - nr_tus);
+      /* Only allow type symbols in type units.  */
+      size_t size_for_kind = (symbol_kind == GDB_INDEX_SYMBOL_KIND_TYPE
+                             ? nr_cus + nr_tus
+                             : nr_cus);
+      if (cu_index >= size_for_kind)
        {
          complaint (_(".gdb_index entry has bad CU index"
                       " [in module %s]"), objfile_name
(per_objfile->objfile));
...
by assuming there are only type symbols in the type units, which means for
other symbols we can be more strict about the allowed indices.

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