[{"id":3673797,"web_url":"http://patchwork.ozlabs.org/comment/3673797/","msgid":"<7b51ad8c-ea46-457d-ad8b-9aa238a2e41e@redhat.com>","list_archive_url":null,"date":"2026-04-06T16:37:27","subject":"Re: [PATCH] c++, v2: Fix up handling of for-range-decls of expansion\n stmt [PR124488]","submitter":{"id":4337,"url":"http://patchwork.ozlabs.org/api/people/4337/","name":"Jason Merrill","email":"jason@redhat.com"},"content":"On 4/6/26 2:16 AM, Jakub Jelinek wrote:\n> On Fri, Apr 03, 2026 at 06:03:22PM -0400, Jason Merrill wrote:\n>>> + if (VAR_P (range_decl))\n>>> + {\n>>> + DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (range_decl) = 1;\n>>> + if (decl_maybe_constant_var_p (range_decl)\n>>> +\t /* FIXME setting TREE_CONSTANT on refs breaks the back end. */\n>>> +\t && !TYPE_REF_P (TREE_TYPE (range_decl)))\n>>> +\tTREE_CONSTANT (range_decl) = true;\n>>> + /* Make it value dependent. */\n>>> + retrofit_lang_decl (range_decl);\n>>> + SET_DECL_DEPENDENT_INIT_P (range_decl, 1);\n>>> + DECL_INITIAL (range_decl) = for_range_identifier;\n>>\n>> Why is the dummy DECL_INITIAL needed as well as DECL_DEPENDENT_INIT_P?\n> \n> I was just afraid something might have called value_dependent_expression_p\n> also on the DECL_INITIAL and for NULL_TREE it returns false.\n> \n> But I have nothing in the testsuite that would need it, so here is an\n> updated patch without that.\n> \n> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?\n\nOK.\n\n> 2026-04-06 Jakub Jelinek \n> \n> \tPR c++/124488\n> \t* parser.cc (cp_parser_expansion_statement): Set\n> \tDECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P, DECL_DEPENDENT_INIT_P and\n> \tif maybe constant non-reference TREE_CONSTANT on range_decl.\n> \t* pt.cc (tsubst_stmt) : Set\n> \tDECL_DEPENDENT_INIT_P on decl.\n> \n> \t* g++.dg/cpp26/expansion-stmt33.C: New test.\n> \n> --- gcc/cp/parser.cc.jj\t2026-03-18 06:35:08.369968785 +0100\n> +++ gcc/cp/parser.cc\t2026-03-20 10:24:40.519275212 +0100\n> @@ -16677,6 +16677,20 @@ cp_parser_expansion_statement (cp_parser\n> TEMPLATE_FOR_EXPR (r) = expansion_init;\n> TEMPLATE_FOR_BODY (r) = do_pushlevel (sk_block);\n> \n> + /* We don't know yet if range_decl will be initialized by constant\n> + expression or not. */\n> + if (VAR_P (range_decl))\n> + {\n> + DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (range_decl) = 1;\n> + if (decl_maybe_constant_var_p (range_decl)\n> +\t /* FIXME setting TREE_CONSTANT on refs breaks the back end. */\n> +\t && !TYPE_REF_P (TREE_TYPE (range_decl)))\n> +\tTREE_CONSTANT (range_decl) = true;\n> + /* Make it value dependent. */\n> + retrofit_lang_decl (range_decl);\n> + SET_DECL_DEPENDENT_INIT_P (range_decl, 1);\n> + }\n> +\n> /* Parse the body of the expansion-statement. */\n> parser->in_statement = IN_EXPANSION_STMT;\n> bool prev = note_iteration_stmt_body_start ();\n> --- gcc/cp/pt.cc.jj\t2026-03-18 06:35:08.372968734 +0100\n> +++ gcc/cp/pt.cc\t2026-03-20 10:24:49.890114568 +0100\n> @@ -19776,6 +19776,11 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t complain, tree in_decl)\n> \t orig_decl = TREE_VEC_ELT (orig_decl, 0);\n> \t tree decl = tsubst (orig_decl, args, complain, in_decl);\n> \t maybe_push_decl (decl);\n> +\t if (VAR_P (decl))\n> +\t {\n> +\t\tretrofit_lang_decl (decl);\n> +\t\tSET_DECL_DEPENDENT_INIT_P (decl, 1);\n> +\t }\n> \n> \t cp_decomp decomp_d, *decomp = NULL;\n> \t if (DECL_DECOMPOSITION_P (decl))\n> --- gcc/testsuite/g++.dg/cpp26/expansion-stmt33.C.jj\t2026-03-20 10:02:54.569810934 +0100\n> +++ gcc/testsuite/g++.dg/cpp26/expansion-stmt33.C\t2026-03-20 10:27:18.603565158 +0100\n> @@ -0,0 +1,17 @@\n> +// PR c++/124488\n> +// { dg-do compile { target c++11 } }\n> +// { dg-options \"\" }\n> +\n> +void\n> +foo ()\n> +{\n> + template for (constexpr int a : { 42 })\t// { dg-warning \"'template for' only available with\" \"\" { target c++23_down } }\n> + auto b = [] () { return a; };\n> +}\n> +\n> +void\n> +bar (int x)\n> +{\n> + template for (const int a : { 42, ++x, 5 })\t// { dg-warning \"'template for' only available with\" \"\" { target c++23_down } }\n> + const int b = a;\n> +}\n> \n> \n> \tJakub\n>","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=IzsEPkrV;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; helo=vm01.sourceware.org;\n envelope-from=gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org;\n receiver=patchwork.ozlabs.org)","sourceware.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=IzsEPkrV","sourceware.org; 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