[binutils-gdb] Fix use of "main" marker in gdb index

[Tom Tromey]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=f283e80fed61096b39c17dc325ad13926aaafef0

commit f283e80fed61096b39c17dc325ad13926aaafef0
Author: Tom Tromey <tom@tromey.com>
Date:   Mon Sep 22 09:08:46 2025 -0600

    Fix use of "main" marker in gdb index
    
    Tom de Vries noticed that with .gdb_index, the "main" marker would
    sometimes seemingly be ignored.
    
    I tracked this down to an interaction between the rewritten reader and
    the "main"-finding code in cooked_index.  With the ordinary DWARF
    scanner, a C "main" won't be marked as IS_MAIN; whereas with
    .gdb_index this can happen.  In this case, the code thinks that C
    requires canonicalization (which is only true for types), and skips
    using the symbol.
    
    This patch fixes the problem and adds some comments explaining what is
    going on.
    
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33441

Diff:
---
 gdb/dwarf2/cooked-index-shard.c |  3 ++-
 gdb/dwarf2/cooked-index.c       | 19 +++++--------------
 2 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/gdb/dwarf2/cooked-index-shard.c b/gdb/dwarf2/cooked-index-shard.c
index e440d85e1c9..58a02316e63 100644
--- a/gdb/dwarf2/cooked-index-shard.c
+++ b/gdb/dwarf2/cooked-index-shard.c
@@ -224,7 +224,8 @@ cooked_index_shard::finalize (const parent_map_map *parent_maps)
 	}
 
       /* Note that this code must be kept in sync with
-	 language_requires_canonicalization.  */
+	 cooked_index::get_main -- if canonicalization is required
+	 here, then a check might be required there.  */
       gdb_assert (entry->canonical == nullptr);
       if ((entry->flags & IS_LINKAGE) != 0)
 	entry->canonical = entry->name;
diff --git a/gdb/dwarf2/cooked-index.c b/gdb/dwarf2/cooked-index.c
index 6209590febb..fbcfe8ff3b6 100644
--- a/gdb/dwarf2/cooked-index.c
+++ b/gdb/dwarf2/cooked-index.c
@@ -32,19 +32,6 @@
    here, and then these are all waited for before exit proceeds.  */
 static gdb::unordered_set<cooked_index *> active_vectors;
 
-/* Return true if LANG requires canonicalization.  This is used
-   primarily to work around an issue computing the name of "main".
-   This function must be kept in sync with
-   cooked_index_shard::finalize.  */
-
-static bool
-language_requires_canonicalization (enum language lang)
-{
-  return (lang == language_ada
-	  || lang == language_c
-	  || lang == language_cplus);
-}
-
 cooked_index::cooked_index (cooked_index_worker_up &&worker)
   : m_state (std::move (worker))
 {
@@ -201,7 +188,11 @@ cooked_index::get_main () const
 	{
 	  if ((entry->flags & IS_MAIN) != 0)
 	    {
-	      if (!language_requires_canonicalization (entry->lang))
+	      /* This should be kept in sync with
+		 cooked_index_shard::finalize.  Note that there, C
+		 requires canonicalization -- but that is only for
+		 types, 'main' doesn't count.  */
+	      if (entry->lang != language_ada && entry->lang != language_cplus)
 		{
 		  /* There won't be one better than this.  */
 		  return entry;