Re: [PATCH][gdb/symtab] Handle .gdb_index in ada language mode

[Tom de Vries <tdevries@suse.de>]

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On 19-05-2020 22:32, Tom Tromey wrote:
>>>>>> "Tom" == Tom de Vries <tdevries@suse.de> writes:
> 
> Tom> Fix the inconsistency by completing implementation of
> Tom> dw2_map_matching_symbols.
> 
> Thanks for doing this.
> 
> Tom> Tested on x86_64-linux, both with native and target board
> Tom> cc-with-debug-index.
> 
> Tom> Any comments?
> 
> This may be the only barrier to supporting Ada in .gdb_index.
> So, it seems like the Ada check in dwarf2/index-write.c should probably
> be removed as well...?
> 
> I'm not 100% sure whether it will work or not.

Using this patch, I managed to get it working.

The patch does the following:
- enable ada .gdb_index by removing the ada check in write_psymbols
- copy some ada-specific code from debug_names::insert to
  write_psymbols
- disable a workaround for gold/15646 in dw2_expand_marked_cus

As for the disabled workaround, I ran into trouble in
gdb.ada/access_tagged_param.exp, where setting a breakpoint on foo failed.

The index shows that there are two entries for foo, one variable, one
function:
...
[3733] foo:
        3 [global, variable]
        5 [global, function]
...
The workaround skips the function, so disabling the workaround allows
the test to pass (my guess atm is that the workaround is not precise
enough).

FWIW, if I use .debug_names instead, I see the same pattern:
...
[445] #0b887389 foo:
        <6> DW_TAG_subprogram DW_IDX_compile_unit=5 DW_IDX_GNU_external=1
        <2> DW_TAG_variable DW_IDX_compile_unit=3 DW_IDX_GNU_external=1
...

Thanks,
- Tom

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try

---
 gdb/dwarf2/index-write.c | 34 ++++++++++++++++++++++++++++++----
 gdb/dwarf2/read.c        | 12 ------------
 2 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/gdb/dwarf2/index-write.c b/gdb/dwarf2/index-write.c
index eabfe5d682..3e83e3ae2c 100644
--- a/gdb/dwarf2/index-write.c
+++ b/gdb/dwarf2/index-write.c
@@ -543,18 +543,44 @@ write_psymbols (struct mapped_symtab *symtab,
   for (; count-- > 0; ++psymp)
     {
       struct partial_symbol *psym = *psymp;
+      const char *name = psym->ginfo.search_name ();
 
       if (psym->ginfo.language () == language_ada)
-	error (_("Ada is not currently supported by the index; "
-		 "use the DWARF 5 index instead"));
+	{
+	  /* We want to ensure that the Ada main function's name appears
+	     verbatim in the index.  However, this name will be of the
+	     form "_ada_mumble", and will be rewritten by ada_decode.
+	     So, recognize it specially here and add it to the index by
+	     hand.  */
+	  if (strcmp (main_name (), name) == 0)
+	    {
+	      gdb_index_symbol_kind kind = symbol_kind (psym);
+
+	      add_index_entry (symtab, name, is_static, kind, cu_index);
+	    }
+
+	  /* In order for the index to work when read back into gdb, it
+	     has to supply a funny form of the name: it should be the
+	     encoded name, with any suffixes stripped.  Using the
+	     ordinary encoded name will not work properly with the
+	     searching logic in find_name_components_bounds; nor will
+	     using the decoded name.  Furthermore, an Ada "verbatim"
+	     name (of the form "<MumBle>") must be entered without the
+	     angle brackets.  Note that the current index is unusual,
+	     see PR symtab/24820 for details.  */
+	  std::string decoded = ada_decode (name);
+	  if (decoded[0] == '<')
+	    name = (char *) strndup (decoded.c_str () + 1, decoded.length () - 2);
+	  else
+	    name = strdup (ada_encode (decoded.c_str ()));
+	}
 
       /* Only add a given psymbol once.  */
       if (psyms_seen.insert (psym).second)
 	{
 	  gdb_index_symbol_kind kind = symbol_kind (psym);
 
-	  add_index_entry (symtab, psym->ginfo.search_name (),
-			   is_static, kind, cu_index);
+	  add_index_entry (symtab, name, is_static, kind, cu_index);
 	}
     }
 }
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index ded71f53b5..d25e8ecb8c 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -4514,7 +4514,6 @@ dw2_expand_marked_cus
    search_domain kind)
 {
   offset_type *vec, vec_len, vec_idx;
-  bool global_seen = false;
   mapped_index &index = *dwarf2_per_objfile->index_table;
 
   vec = (offset_type *) (index.constant_pool
@@ -4523,8 +4522,6 @@ dw2_expand_marked_cus
   for (vec_idx = 0; vec_idx < vec_len; ++vec_idx)
     {
       offset_type cu_index_and_attrs = MAYBE_SWAP (vec[vec_idx + 1]);
-      /* This value is only valid for index versions >= 7.  */
-      int is_static = GDB_INDEX_SYMBOL_STATIC_VALUE (cu_index_and_attrs);
       gdb_index_symbol_kind symbol_kind =
 	GDB_INDEX_SYMBOL_KIND_VALUE (cu_index_and_attrs);
       int cu_index = GDB_INDEX_CU_VALUE (cu_index_and_attrs);
@@ -4536,15 +4533,6 @@ dw2_expand_marked_cus
 	(index.version >= 7
 	 && symbol_kind != GDB_INDEX_SYMBOL_KIND_NONE);
 
-      /* Work around gold/15646.  */
-      if (attrs_valid)
-	{
-	  if (!is_static && global_seen)
-	    continue;
-	  if (!is_static)
-	    global_seen = true;
-	}
-
       /* Only check the symbol's kind if it has one.  */
       if (attrs_valid)
 	{