[{"id":3680010,"web_url":"http://patchwork.ozlabs.org/comment/3680010/","msgid":"","list_archive_url":null,"date":"2026-04-21T18:06:47","subject":"Re: [PATCH] c: Fix counted_by attribute error recovery [PR124969]","submitter":{"id":14370,"url":"http://patchwork.ozlabs.org/api/people/14370/","name":"Marek Polacek","email":"polacek@redhat.com"},"content":"On Tue, Apr 21, 2026 at 07:31:01PM +0200, Jakub Jelinek wrote:\n> Hi!\n> \n> The last patch made me try also pointer arithmetics on incomplete\n> type. And here we ICE before actually diagnosing the error\n> because we try to dereference element_size.\n> \n> Furthermore, TYPE_SIZE_UNIT (element_type) is in sizetype, so\n> we shouldn't use build_one_cst (size_type_node) for the void *\n> case, but size_one_node (aka size_int (1)).\n> \n> Ok for trunk if it passes full bootstrap/regtest?\n> \n> 2026-04-21 Jakub Jelinek \n> \n> \tPR sanitizer/124969\n> \t* c-typeck.cc (build_access_with_size_for_counted_by): Use\n> \tsize_one_node instead of build_one_cst (size_type_node). Punt\n> \tif element_size is NULL_TREE.\n> \n> \t* gcc.dg/ubsan/pr124969-2.c: New test.\n> \n> --- gcc/c/c-typeck.cc.jj\t2026-04-01 19:09:38.324343805 +0200\n> +++ gcc/c/c-typeck.cc\t2026-04-21 19:16:20.325644120 +0200\n> @@ -3270,8 +3270,10 @@ build_access_with_size_for_counted_by (l\n> \n> tree element_type = TREE_TYPE (TREE_TYPE (ref));\n> tree element_size = VOID_TYPE_P (element_type)\n> -\t\t ? build_one_cst (size_type_node)\n> +\t\t ? size_one_node\n> \t\t : TYPE_SIZE_UNIT (element_type);\n> + if (element_size == NULL_TREE)\n> + return ref;\n\nI wasn't sure what the right thing to return would be here, but returning\nNULL_TREE would ICE elsewhere. So, OK.\n \n> tree first_param = is_fam\n> \t\t ? c_fully_fold (array_to_pointer_conversion (loc, ref),\n> --- gcc/testsuite/gcc.dg/ubsan/pr124969-2.c.jj\t2026-04-21 19:19:31.114417366 +0200\n> +++ gcc/testsuite/gcc.dg/ubsan/pr124969-2.c\t2026-04-21 19:20:29.357432321 +0200\n> @@ -0,0 +1,15 @@\n> +/* PR sanitizer/124969 */\n> +/* { dg-do compile } */\n> +/* { dg-options \"-fsanitize=undefined\" } */\n> +\n> +struct T;\n> +struct S {\n> + int c;\n> + struct T *b __attribute__ ((counted_by (c)));\n> +} a;\n> +\n> +void *\n> +foo ()\n> +{\n> + return a.b + 10;\t/* { dg-error \"invalid use of undefined type 'struct T'\" } */\n> +}\n> \n> \tJakub\n> \n\nMarek","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=XaW21tpn;\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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