[{"id":3682139,"web_url":"http://patchwork.ozlabs.org/comment/3682139/","msgid":"","list_archive_url":null,"date":"2026-04-24T16:56:26","subject":"Re: [PATCH] c++/modules: defer completion of streamed-in cNTTPs\n [PR124953]","submitter":{"id":4337,"url":"http://patchwork.ozlabs.org/api/people/4337/","name":"Jason Merrill","email":"jason@redhat.com"},"content":"On 4/24/26 11:01 AM, Patrick Palka wrote:\n> Tested on x86_64-pc-linux-gnu, does this look OK for trunk/16.2?\n\nOK.\n\n> -- >8 --\n> \n> Here we hit lazy loading recursion when streaming in the cNTTP object\n> wrap{}, via get_template_parm_object -> cp_finish_decl ->\n> ensure_literal_type_for_constexpr_object -> complete_type, apparently\n> the class definition of wrap hasn't been streamed in yet.\n> If we disable that literal type check for NTTP objects, we still hit\n> recursion, from layout_var_decl.\n> \n> It seems prudent to defer calling cp_finish_decl for NTTP objects until\n> after lazy loading has completed like we do for expand_or_defer_fn and\n> cdtors. This patch arranges that, as a follow-up to the previous fixes\n> r15-3031 and r16-318 for NTTP object streaming.\n> \n> \tPR c++/124953\n> \n> gcc/cp/ChangeLog:\n> \n> \t* module.cc (trees_in::tree_node) : Push the result\n> \tof get_template_parm_object to post_load_decls.\n> \t(post_load_processing): Call cp_finish_decl on any not yet\n> \tcompleted NTTP objects.\n> \t* pt.cc (get_template_parm_object): Don't call cp_finish_decl\n> \twhen !check_init.\n> \n> gcc/testsuite/ChangeLog:\n> \n> \t* g++.dg/modules/tpl-nttp-3_a.H: New test.\n> \t* g++.dg/modules/tpl-nttp-3_b.C: New test.\n> ---\n> gcc/cp/module.cc | 12 ++++++++++++\n> gcc/cp/pt.cc | 3 +++\n> gcc/testsuite/g++.dg/modules/tpl-nttp-3_a.H | 11 +++++++++++\n> gcc/testsuite/g++.dg/modules/tpl-nttp-3_b.C | 5 +++++\n> 4 files changed, 31 insertions(+)\n> create mode 100644 gcc/testsuite/g++.dg/modules/tpl-nttp-3_a.H\n> create mode 100644 gcc/testsuite/g++.dg/modules/tpl-nttp-3_b.C\n> \n> diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc\n> index 98a285201d00..4d6df0564d91 100644\n> --- a/gcc/cp/module.cc\n> +++ b/gcc/cp/module.cc\n> @@ -10872,6 +10872,7 @@ trees_in::tree_node (bool is_use)\n> \t int tag = insert (res);\n> \t dump (dumper::TREE)\n> \t && dump (\"Created nttp object:%d %N\", tag, name);\n> +\t vec_safe_push (post_load_decls, res);\n> \t }\n> }\n> break;\n> @@ -20531,6 +20532,17 @@ post_load_processing ()\n> \n> dump () && dump (\"Post-load processing of %N\", decl);\n> \n> + if (VAR_P (decl) && DECL_NTTP_OBJECT_P (decl))\n> +\t{\n> +\t if (!DECL_SIZE (decl))\n> +\t {\n> +\t push_to_top_level ();\n> +\t cp_finish_decl (decl, DECL_INITIAL (decl), false, NULL_TREE, 0);\n> +\t pop_from_top_level ();\n> +\t }\n> +\t continue;\n> +\t}\n> +\n> gcc_checking_assert (DECL_MAYBE_IN_CHARGE_CDTOR_P (decl));\n> expand_or_defer_fn (decl);\n> /* As in module_state::read_cluster. */\n> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc\n> index fca63d3950dd..ce324c87ecf8 100644\n> --- a/gcc/cp/pt.cc\n> +++ b/gcc/cp/pt.cc\n> @@ -7582,6 +7582,9 @@ get_template_parm_object (tree expr, tree name, bool check_init/*=true*/)\n> /* FIXME setting TREE_CONSTANT on refs breaks the back end. */\n> if (!TYPE_REF_P (type))\n> \tTREE_CONSTANT (decl) = true;\n> + pushdecl_top_level (decl);\n> + /* The caller must call cp_finish_decl to complete its processing. */\n> + return decl;\n> }\n> \n> pushdecl_top_level_and_finish (decl, expr);\n> diff --git a/gcc/testsuite/g++.dg/modules/tpl-nttp-3_a.H b/gcc/testsuite/g++.dg/modules/tpl-nttp-3_a.H\n> new file mode 100644\n> index 000000000000..1b28780b14b6\n> --- /dev/null\n> +++ b/gcc/testsuite/g++.dg/modules/tpl-nttp-3_a.H\n> @@ -0,0 +1,11 @@\n> +// PR c++/124953\n> +// { dg-do compile { target c++20 } }\n> +// { dg-additional-options \"-fmodule-header\" }\n> +\n> +template struct wrap { using type = T; };\n> +template using unwrap = decltype(V)::type;\n> +\n> +struct Foo {\n> + struct Storage {};\n> + unwrap{}> data_{};\n> +};\n> diff --git a/gcc/testsuite/g++.dg/modules/tpl-nttp-3_b.C b/gcc/testsuite/g++.dg/modules/tpl-nttp-3_b.C\n> new file mode 100644\n> index 000000000000..2a51186c64d3\n> --- /dev/null\n> +++ b/gcc/testsuite/g++.dg/modules/tpl-nttp-3_b.C\n> @@ -0,0 +1,5 @@\n> +// PR c++/124953\n> +// { dg-do compile { target c++20 } }\n> +// { dg-additional-options \"-fmodules -fno-module-lazy\" }\n> +\n> +import \"tpl-nttp-3_a.H\";","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=aVcbgl3O;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=38.145.34.32; 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