On Tue, 10 Mar 2015, Marek Polacek wrote:
> I'd like to backport the following patch that suppresses bogus ubsan errors.
> I had to tweak the testcase a bit since 4.9 doesn't know
> -fno-sanitize-recover.
>
> Bootstrapped/regtested on x86_64-linux, ok for 4.9?
Ok.
Thanks,
Richard.
> 2015-03-10 Marek Polacek <pola...@redhat.com>
>
> Backported from mainline
> 2014-12-04 Marek Polacek <pola...@redhat.com>
>
> PR middle-end/56917
> * fold-const.c (fold_unary_loc): Perform the negation in A's type
> when transforming ~ (A - 1) or ~ (A + -1) to -A.
>
> * c-c++-common/ubsan/pr56917.c: New test.
>
> --- gcc/fold-const.c
> +++ gcc/fold-const.c
> @@ -8324,9 +8324,14 @@ fold_unary_loc (location_t loc, enum tree_code code,
> tree type, tree op0)
> && integer_onep (TREE_OPERAND (arg0, 1)))
> || (TREE_CODE (arg0) == PLUS_EXPR
> && integer_all_onesp (TREE_OPERAND (arg0, 1)))))
> - return fold_build1_loc (loc, NEGATE_EXPR, type,
> - fold_convert_loc (loc, type,
> - TREE_OPERAND (arg0, 0)));
> + {
> + /* Perform the negation in ARG0's type and only then convert
> + to TYPE as to avoid introducing undefined behavior. */
> + tree t = fold_build1_loc (loc, NEGATE_EXPR,
> + TREE_TYPE (TREE_OPERAND (arg0, 0)),
> + TREE_OPERAND (arg0, 0));
> + return fold_convert_loc (loc, type, t);
> + }
> /* Convert ~(X ^ Y) to ~X ^ Y or X ^ ~Y if ~X or ~Y simplify. */
> else if (TREE_CODE (arg0) == BIT_XOR_EXPR
> && (tem = fold_unary_loc (loc, BIT_NOT_EXPR, type,
> --- gcc/testsuite/c-c++-common/ubsan/pr56917.c
> +++ gcc/testsuite/c-c++-common/ubsan/pr56917.c
> @@ -0,0 +1,43 @@
> +/* PR middle-end/56917 */
> +/* { dg-do run } */
> +/* { dg-options "-fsanitize=undefined" } */
> +
> +#include <stdio.h>
> +
> +#define INT_MIN (-__INT_MAX__ - 1)
> +#define LONG_MIN (-__LONG_MAX__ - 1L)
> +#define LLONG_MIN (-__LONG_LONG_MAX__ - 1LL)
> +
> +int __attribute__ ((noinline,noclone))
> +fn1 (unsigned int u)
> +{
> + return (-(int) (u - 1U)) - 1;
> +}
> +
> +long __attribute__ ((noinline,noclone))
> +fn2 (unsigned long int ul)
> +{
> + return (-(long) (ul - 1UL)) - 1L;
> +}
> +
> +long long __attribute__ ((noinline,noclone))
> +fn3 (unsigned long long int ull)
> +{
> + return (-(long long) (ull - 1ULL)) - 1LL;
> +}
> +
> +int
> +main (void)
> +{
> + fputs ("UBSAN TEST START\n", stderr);
> +
> + if (fn1 (__INT_MAX__ + 1U) != INT_MIN
> + || fn2 (__LONG_MAX__ + 1UL) != LONG_MIN
> + || fn3 (__LONG_LONG_MAX__ + 1ULL) != LLONG_MIN)
> + __builtin_abort ();
> +
> + fputs ("UBSAN TEST END\n", stderr);
> + return 0;
> +}
> +
> +/* { dg-output "UBSAN TEST START(\n|\r\n|\r)UBSAN TEST END" } */
>
> Marek
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Jennifer Guild,
Dilip Upmanyu, Graham Norton HRB 21284 (AG Nuernberg)
