[PATCH] Backport ubsan fix to 4.9

[PATCH] Backport ubsan fix to 4.9

[Marek Polacek]

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?

2015-03-10  Marek Polacek  <polacek@redhat.com>

	Backported from mainline
	2014-12-04  Marek Polacek  <polacek@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

Re: [PATCH] Backport ubsan fix to 4.9

[Richard Biener]

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  <polacek@redhat.com>
> 
> 	Backported from mainline
> 	2014-12-04  Marek Polacek  <polacek@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 <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Jennifer Guild,
Dilip Upmanyu, Graham Norton HRB 21284 (AG Nuernberg)