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Re: [PATCH] Fix PR56990


On 2013-04-22 17:21, Jakub Jelinek wrote:
On Mon, Apr 22, 2013 at 06:11:26PM +0200, Marek Polacek wrote:
We're getting SIGFPE, because one simply does not divide by zero.
Fixed by doing the modulo only when size != 0.

Regtested/bootstrapped on x86_64-linux, ok for trunk and 4.8?

2013-04-22  Marek Polacek  <polacek@redhat.com>

	PR sanitizer/56990
	* tsan.c (instrument_expr): Don't count modulo if the size
	is zero.

	* gcc.dg/pr56990.c: New test.

--- gcc/tsan.c.mp	2013-04-19 15:39:46.416450528 +0200
+++ gcc/tsan.c	2013-04-22 17:23:54.115647673 +0200
@@ -131,7 +131,8 @@ instrument_expr (gimple_stmt_iterator gs
    if (TREE_READONLY (base))
      return false;

-  if (bitpos % (size * BITS_PER_UNIT)
+  if ((size != 0

IMHO for size == 0 we should return false too, there is no store or read to
be instrumented.  So
     if (size == 0
	|| bitpos % (size * BITS_PER_UNIT)
	|| bitsize != size * BITS_PER_UNIT)
       return false;
?

Point.  And along those lines, will we ever have bitsize == 0?
If not, then just swapping the conditions is sufficient:


r~


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