[{"id":3677381,"web_url":"http://patchwork.ozlabs.org/comment/3677381/","msgid":"<240bc543-080a-4242-9c22-c9f493d1891a@redhat.com>","list_archive_url":null,"date":"2026-04-14T19:59:59","subject":"Re: [PATCH] c++: Check base accessibility in cp_decomp_size\n [PR124862]","submitter":{"id":4337,"url":"http://patchwork.ozlabs.org/api/people/4337/","name":"Jason Merrill","email":"jason@redhat.com"},"content":"On 4/14/26 2:50 AM, Jakub Jelinek wrote:\n> Hi!\n> \n> clang in __builtin_structured_binding_size checks whether base which\n> contains the destructible members is accessible.\n> In cp_finish_decomp we call:\n> if (type != btype)\n> {\n> t = convert_to_base (t, btype, /*check_access*/true,\n> /*nonnull*/false, tf_warning_or_error);\n> type = btype;\n> }\n> which calls lookup_base which diagnoses that. The following patch\n> just calls lookup_base in that case.\n> \n> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?\n\nOK.\n\n> 2026-04-14 Jakub Jelinek \n> \n> \tPR c++/124862\n> \t* decl.cc (cp_decomp_size): If btype is different from type,\n> \tcheck if it is accessible.\n> \n> \t* g++.dg/ext/builtin-structured-binding-size5.C: New test.\n> \t* g++.dg/ext/builtin-structured-binding-size6.C: New test.\n> \n> --- gcc/cp/decl.cc.jj\t2026-04-08 07:46:31.098631631 +0200\n> +++ gcc/cp/decl.cc\t2026-04-13 10:47:38.170670623 +0200\n> @@ -10671,6 +10671,12 @@ cp_decomp_size (location_t loc, tree typ\n> \treturn -1;\n> else if (btype == NULL_TREE)\n> \treturn 0;\n> + if (btype != type)\n> +\t{\n> +\t tree binfo = lookup_base (type, btype, ba_check, NULL, complain);\n> +\t if (binfo == NULL_TREE || binfo == error_mark_node)\n> +\t return -1;\n> +\t}\n> for (tree field = TYPE_FIELDS (btype); field; field = TREE_CHAIN (field))\n> \tif (TREE_CODE (field) != FIELD_DECL\n> \t || DECL_ARTIFICIAL (field)\n> --- gcc/testsuite/g++.dg/ext/builtin-structured-binding-size5.C.jj\t2026-04-13 10:53:55.136222340 +0200\n> +++ gcc/testsuite/g++.dg/ext/builtin-structured-binding-size5.C\t2026-04-13 11:00:39.924299802 +0200\n> @@ -0,0 +1,13 @@\n> +// PR c++/124862\n> +// { dg-do compile { target c++20 } }\n> +\n> +struct S\n> +{\n> + int a = 0, b = 0, c = 0;\n> +};\n> +\n> +struct T : private S\n> +{};\n> +\n> +static_assert (__builtin_structured_binding_size (S) == 3);\n> +auto a = __builtin_structured_binding_size (T);\t\t// { dg-error \"'S' is an inaccessible base of 'T'\" }\n> --- gcc/testsuite/g++.dg/ext/builtin-structured-binding-size6.C.jj\t2026-04-13 10:54:38.765476033 +0200\n> +++ gcc/testsuite/g++.dg/ext/builtin-structured-binding-size6.C\t2026-04-13 10:55:37.163477088 +0200\n> @@ -0,0 +1,16 @@\n> +// PR c++/124862\n> +// { dg-do compile { target c++20 } }\n> +\n> +struct S\n> +{\n> + int a = 0, b = 0, c = 0;\n> +};\n> +\n> +struct T : private S\n> +{};\n> +\n> +template \n> +concept is_destructurable = requires { { __builtin_structured_binding_size (T) }; };\n> +\n> +static_assert (is_destructurable );\n> +static_assert (!is_destructurable );\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=cTQXSSpZ;\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=cTQXSSpZ","sourceware.org; dmarc=pass (p=quarantine dis=none)\n header.from=redhat.com","sourceware.org; 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