[RFC][PR symtab/30520] gdb/symtab: check name matches before expanding a CU

[Dmitry Neverov <dmitry.neverov@jetbrains.com>]

From: "Dmitry.Neverov" <dmitry.neverov@jetbrains.com>

The added check fixes the case when an unqualified lookup
name without template arguments causes expansion of many CUs
which contain the name with template arguments.

This is similar to what dw2_expand_symtabs_matching_symbol does
before expanding the CU.

In the referenced issue the lookup name was wxObjectDataPtr and many
CUs had names like wxObjectDataPtr<wxBitmapBundleImpl>. This caused
their expansion and the lookup took around a minute. The added check
helps to avoid the expansion and makes the symbol lookup to return in
a second or so.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30520
---
 gdb/dwarf2/read.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 1b5e566bb01..ccb32f152b0 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -16882,9 +16882,24 @@ cooked_index_functions::expand_symtabs_matching
 		= lookup_name_without_params.match_type ();
 	      if ((match_type == symbol_name_match_type::FULL
 		   || (lang != language_ada
-		       && match_type == symbol_name_match_type::EXPRESSION))
-		  && parent != nullptr)
-		continue;
+		       && match_type == symbol_name_match_type::EXPRESSION)))
+		{
+		  if (parent != nullptr)
+		    continue;
+
+		  enum language cu_lang = entry->per_cu->lang (false);
+		  if (cu_lang != language_unknown)
+		  {
+		    const language_defn *lang_def = language_def (cu_lang);
+		    symbol_name_matcher_ftype *name_matcher
+		      = lang_def->get_symbol_name_matcher
+		      (lookup_name_without_params);
+		    auto_obstack temp_storage;
+		    if (!name_matcher (entry->full_name(&temp_storage),
+				       lookup_name_without_params, nullptr))
+		      continue;
+		  }
+	      }
 	    }
 	  else
 	    {
-- 
2.39.2