From 5c2a5bfcd4e62daeb7d7f25db088816fd1d54194 Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Wed, 28 Jan 2026 09:48:10 +0100
Subject: [PATCH] free-lang-data: Remove C++ annotations [PR123837]

As mentioned in the PR and reproduced on the testcase, we ICE during
LTO streaming because C++ annotation arguments can contain trees LTO
streaming doesn't handle.
We don't really need annotations when the FE is done with the whole
TU, annotations are always TU local and not exposed to the rest and
used in consteval only stuff, so the following patch just removes
all annotations at free-lang-data time.

2026-01-28  Jakub Jelinek  <jakub@redhat.com>

	PR c++/123837
	* ipa-free-lang-data.cc (find_decls_types_r): Remove C++ annotations
	from {DECL,TYPE}_ATRIBUTES.

	* g++.dg/reflect/annotations9.C: New test.
---
 gcc/ipa-free-lang-data.cc                   |  8 ++++++++
 gcc/testsuite/g++.dg/reflect/annotations9.C | 14 ++++++++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/reflect/annotations9.C

diff --git a/gcc/ipa-free-lang-data.cc b/gcc/ipa-free-lang-data.cc
index edc4f1aed81..f32563fdd22 100644
--- a/gcc/ipa-free-lang-data.cc
+++ b/gcc/ipa-free-lang-data.cc
@@ -730,6 +730,10 @@ find_decls_types_r (tree *tp, int *ws, void *data)
       if (TREE_CODE (t) != TYPE_DECL)
 	fld_worklist_push (DECL_INITIAL (t), fld);
 
+      /* Remove C++ annotations, those aren't needed for LTO and contain
+	 trees we sometimes can't stream.  */
+      DECL_ATTRIBUTES (t)
+	= remove_attribute ("annotation ", DECL_ATTRIBUTES (t));
       fld_worklist_push (DECL_ATTRIBUTES (t), fld);
       fld_worklist_push (DECL_ABSTRACT_ORIGIN (t), fld);
 
@@ -763,6 +767,10 @@ find_decls_types_r (tree *tp, int *ws, void *data)
 	fld_worklist_push (TYPE_CACHED_VALUES (t), fld);
       fld_worklist_push (TYPE_SIZE (t), fld);
       fld_worklist_push (TYPE_SIZE_UNIT (t), fld);
+      /* Remove C++ annotations, those aren't needed for LTO and contain
+	 trees we sometimes can't stream.  */
+      TYPE_ATTRIBUTES (t)
+	= remove_attribute ("annotation ", TYPE_ATTRIBUTES (t));
       fld_worklist_push (TYPE_ATTRIBUTES (t), fld);
       fld_worklist_push (TYPE_POINTER_TO (t), fld);
       fld_worklist_push (TYPE_REFERENCE_TO (t), fld);
diff --git a/gcc/testsuite/g++.dg/reflect/annotations9.C b/gcc/testsuite/g++.dg/reflect/annotations9.C
new file mode 100644
index 00000000000..32078f281e1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/annotations9.C
@@ -0,0 +1,14 @@
+// PR c++/123837
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+// { dg-additional-options "-flto" { target lto } }
+
+struct A {};
+[[=A {}]] int a {};
+struct [[=A {}]] B { int b; };
+B b {};
+
+int
+main ()
+{
+}