File gdb-symtab-cache-dw2_get_file_names-result-for-dummy.patch of Package gdb

From c7e0fde828e5b2d5fb22c11ad4cf0dcfc6de0292 Mon Sep 17 00:00:00 2001
From: Tom de Vries <tdevries@suse.de>
Date: Wed, 14 Jan 2026 21:47:05 +0100
Subject: [PATCH 3/4] [gdb/symtab] Cache dw2_get_file_names result for dummy CU

Consider function dw2_get_file_names:
...
static struct quick_file_names *
dw2_get_file_names (dwarf2_per_cu *this_cu, dwarf2_per_objfile *per_objfile)
{
  /* This should never be called for TUs.  */
  gdb_assert (!this_cu->is_debug_types ());

  if (this_cu->files_read)
    return this_cu->file_names;

  cutu_reader reader (*this_cu, *per_objfile, nullptr,
                      per_objfile->get_cu (this_cu), true, language_minimal,
                      nullptr);
  if (!reader.is_dummy ())
    dw2_get_file_names_reader (reader.cu (), reader.top_level_die ());

  return this_cu->file_names;
}
...

If dw2_get_file_names_reader is called, the result is cached in
this_cu->file_names, and this fact is tracked in this_cu->files_read, allowing
subsequent calls to access the cached value.

But for dummy CUs, while the result (nullptr) is cached in
this_cu->file_names, this is not noted in this_cu->files_read, and
consequently subsequent calls will read the top-level DIE in the CU again.

Fix this by setting this_cu->files_read also for dummy CUs.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33777
(cherry picked from commit 5a8351167a8b4547d6583a5d713936c1aec39565) master
(cherry picked from commit 0ac91006f95d5b8dd4c1610069628f31b252a175) gdb-17-branch
---
 gdb/dwarf2/read.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index f4a1eaf0f53..d6722a01376 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -1957,7 +1957,12 @@ dw2_get_file_names (dwarf2_per_cu_data *this_cu,
     return this_cu->file_names;
 
   cutu_reader reader (this_cu, per_objfile);
-  if (!reader.dummy_p)
+  if (reader.dummy_p)
+    {
+      /* Make sure we don't re-read the dummy CU.  */
+      this_cu->files_read = true;
+    }
+  else
     dw2_get_file_names_reader (&reader, reader.comp_unit_die);
 
   return this_cu->file_names;
-- 
2.51.0