[{"id":3678180,"web_url":"http://patchwork.ozlabs.org/comment/3678180/","msgid":"<5caa746b-10db-481e-b0c3-24f44d479210@redhat.com>","list_archive_url":null,"date":"2026-04-16T13:41:33","subject":"Re: [PATCH] c++: Fix up expansion-stmt mangling ICE [PR124120]","submitter":{"id":4337,"url":"http://patchwork.ozlabs.org/api/people/4337/","name":"Jason Merrill","email":"jason@redhat.com"},"content":"On 4/16/26 3:17 AM, Jakub Jelinek wrote:\n> Hi!\n> \n> One of the reflect/* tests ICEs on Solaris but not on Linux (at least not\n> when using recent glibc).\n> I've tracked it down to a problem with expansion statements, due to the\n> workaround we have for missing part of P2686R4 where we make some artificial\n> vars static. Some of them (the __for_range and __for_begin) have DECL_NAMEs\n> (with a space in it) and so even when they are static, don't cause problems.\n> But the iter variable (in https://eel.is/c++draft/stmt.expand#5.2 ) is when\n> constexpr still static and was nameless.\n> Now, because it is constexpr and not odr used, it is optimized out, but if\n> the TU also contains weakref attribute or something else that requires\n> cgraph to construct assembler_name_hash, we ICE when trying to mangle\n> the iter nameless variable.\n> \n> The following patch fixes that by giving it yet another artificial name.\n> \n> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?\n\nOK\n\n> 2026-04-16 Jakub Jelinek \n> \n> \tPR c++/124120\n> \t* pt.cc (finish_expansion_stmt): Give iter variable an artificial\n> \tname.\n> \n> \t* g++.dg/cpp26/expansion-stmt40.C: New test.\n> \n> --- gcc/cp/pt.cc.jj\t2026-04-15 09:01:57.886372126 +0200\n> +++ gcc/cp/pt.cc\t2026-04-15 14:59:25.084554609 +0200\n> @@ -33664,7 +33664,8 @@ finish_expansion_stmt (tree expansion_st\n> \t if (DECL_DECLARED_CONSTEXPR_P (range_decl)\n> \t && !TYPE_REF_P (iter_type))\n> \t iter_type = cp_build_qualified_type (iter_type, TYPE_QUAL_CONST);\n> -\t iter = build_decl (loc, VAR_DECL, NULL_TREE, iter_type);\n> +\t iter = build_decl (loc, VAR_DECL, get_identifier (\"__for_iter \"),\n> +\t\t\t iter_type);\n> \t TREE_USED (iter) = 1;\n> \t DECL_ARTIFICIAL (iter) = 1;\n> \t if (DECL_DECLARED_CONSTEXPR_P (range_decl))\n> --- gcc/testsuite/g++.dg/cpp26/expansion-stmt40.C.jj\t2026-04-15 15:22:48.992056372 +0200\n> +++ gcc/testsuite/g++.dg/cpp26/expansion-stmt40.C\t2026-04-15 15:43:02.282796097 +0200\n> @@ -0,0 +1,40 @@\n> +// PR c++/124120\n> +// { dg-do compile { target c++14 } }\n> +// { dg-require-weak \"\" }\n> +// { dg-options \"\" }\n> +\n> +struct A\n> +{\n> + int x;\n> + constexpr explicit A (int v) : x(v) {}\n> + constexpr A &operator ++ () { ++x; return *this; }\n> + constexpr int operator * () const { return x; }\n> + constexpr bool operator != (const A &o) const { return x != o.x; }\n> + constexpr A operator + (int o) const { A r (x + o); return r; }\n> + constexpr int operator - (const A &o) const { return x - o.x; }\n> +};\n> +\n> +namespace N\n> +{\n> + struct B { constexpr B () {} };\n> + constexpr A begin (const B &) { return A (0); }\n> + constexpr A end (const B &) { return A (6); }\n> +}\n> +\n> +int\n> +bar ()\n> +{\n> + int r = 0;\n> + template for (constexpr auto i : N::B {})\t\t\t// { dg-warning \"'template for' only available with\" \"\" { target c++23_down } }\n> + r += i;\n> + return r;\n> +}\n> +\n> +extern void plugh ();\n> +\n> +[[gnu::weakref (\"plugh\")]] static void xyzzy ();\n> +\n> +void\n> +plugh ()\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=gpIIerpt;\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; 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