[{"id":3680000,"web_url":"http://patchwork.ozlabs.org/comment/3680000/","msgid":"","list_archive_url":null,"date":"2026-04-21T17:51:17","subject":"Re: [PATCH] c-family: Fix ICE with counted_by attribute [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 07:28:22PM +0200, Jakub Jelinek wrote:\n> Hi!\n> \n> The following valid testcase ICEs, because we try to use\n> TREE_CODE (NULL_TREE).\n> We document that counted_by is supported on pointers to void\n> and that it behaves like the GNU pointer to void arithmetics\n> extension in that case. build_access_with_size_for_counted_by\n> already uses 1 in that case as element_size.\n> \n> The following patch fixes it, plus for error recovery punts\n> if it is a pointer to incomplete type other than void (pointer\n> arithmetics on such type will be diagnosed as error later on).\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-ubsan.cc (get_index_from_pointer_addr_expr): For\n> \tVOID_TYPE_P (pointee_type) use size_one_node instead of\n> \tTYPE_SIZE_UNIT (pointee_type) as pointee_size. Punt if\n> \tpointee_size is NULL_TREE. Formatting fix.\n> \n> \t* gcc.dg/ubsan/pr124969-1.c: New test.\n> \n> --- gcc/c-family/c-ubsan.cc.jj\t2026-03-27 10:17:13.716337560 +0100\n> +++ gcc/c-family/c-ubsan.cc\t2026-04-21 19:02:54.261275681 +0200\n> @@ -741,7 +741,11 @@ get_index_from_pointer_addr_expr (tree p\n> /* Get the pointee type of the call to .ACCESS_WITH_SIZE.\n> This should be the element type of the pointer array. */\n> tree pointee_type = TREE_TYPE (TREE_TYPE (call));\n> - tree pointee_size = TYPE_SIZE_UNIT (pointee_type);\n> + tree pointee_size;\n> + if (VOID_TYPE_P (pointee_type))\n> + pointee_size = size_one_node;\n> + else\n> + pointee_size = TYPE_SIZE_UNIT (pointee_type);\n> \n> tree index_exp = TREE_OPERAND (pointer, 1);\n> *index_p = pointer;\n> @@ -750,6 +754,8 @@ get_index_from_pointer_addr_expr (tree p\n> if (!(TREE_CODE (index_exp) != MULT_EXPR\n> \t&& tree_int_cst_equal (pointee_size, integer_one_node)))\n> {\n> + if (pointee_size == NULL_TREE)\n> +\treturn NULL_TREE;\n\nI won't insist, but could this instead be\n\n if (!COMPLETE_OR_VOID_TYPE_P (pointee_type))\n return NULL_TREE;\n\nabove?\n\n> while (CONVERT_EXPR_CODE_P (TREE_CODE (index_exp)))\n\nNot your problem, but this is CONVERT_EXPR_P.\n\n> \t{\n> \t *index_p = index_exp;\n> @@ -760,7 +766,7 @@ get_index_from_pointer_addr_expr (tree p\n> \t\t\t\t\t index_n, pointee_size);\n> \n> if (!index_exp)\n> - return NULL_TREE;\n> +\treturn NULL_TREE;\n> }\n> \n> while (CONVERT_EXPR_CODE_P (TREE_CODE (index_exp)))\n\nAlso CONVERT_EXPR_P.\n\nI think the patch is OK with or without these changes. Thanks.\n\n> --- gcc/testsuite/gcc.dg/ubsan/pr124969-1.c.jj\t2026-04-21 19:18:43.197227776 +0200\n> +++ gcc/testsuite/gcc.dg/ubsan/pr124969-1.c\t2026-04-21 19:19:23.288549722 +0200\n> @@ -0,0 +1,14 @@\n> +/* PR sanitizer/124969 */\n> +/* { dg-do compile } */\n> +/* { dg-options \"-fsanitize=undefined\" } */\n> +\n> +struct S {\n> + int c;\n> + void *b __attribute__ ((counted_by (c)));\n> +} a;\n> +\n> +void *\n> +foo (void)\n> +{\n> + return a.b + 10;\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=W+TehBl9;\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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