https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126017
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
For the streaming itself it could be something like:
--- a/gcc/lto-streamer-out.cc 2026-07-20 09:57:50.693934604 +0200
+++ b/gcc/lto-streamer-out.cc 2026-09-14 18:51:29.227337823 +0200
@@ -560,6 +560,12 @@ lto_is_streamable (tree expr)
{
enum tree_code code = TREE_CODE (expr);
+ /* Allow streaming C++ std::meta::info. */
+ if (code == LANG_TYPE
+ && TYPE_NAME (expr)
+ && TREE_CODE (TYPE_NAME (expr)) == IDENTIFIER_NODE
+ && id_equal (TYPE_NAME (expr), "decltype(^^int)"))
+ return true;
/* Notice that we reject SSA_NAMEs as well. We only emit the SSA
name version in lto_output_tree_ref (see output_ssa_names). */
return !is_lang_specific (expr)
I wish we haven't abused LANG_TYPE here and really used META_TYPE in the
middle-end.
Because having is_lang_specific return true for LANG_TYPE is natural.
