|
 |
159db5 |
From dd4b061c27dc0865c8f8987d294de6e04b321c18 Mon Sep 17 00:00:00 2001
|
|
|
159db5 |
From: Benjamin Otte <otte@redhat.com>
|
|
|
159db5 |
Date: Sat, 22 Aug 2015 23:06:23 +0200
|
|
|
159db5 |
Subject: [PATCH 2/2] pixops: Be smarter than gcc's optimizer
|
|
|
159db5 |
|
|
|
159db5 |
gcc realizes that the overflow checks aren't necessary. Why not?
|
|
|
159db5 |
|
|
|
159db5 |
Well, if an int overflows, the behavior is undefined. And turning on
|
|
|
159db5 |
-fomit-instructions is valid behavior in an undefined situation.
|
|
|
159db5 |
---
|
|
|
159db5 |
gdk-pixbuf/pixops/pixops.c | 15 +++++++--------
|
|
|
159db5 |
1 file changed, 7 insertions(+), 8 deletions(-)
|
|
|
159db5 |
|
|
|
159db5 |
diff --git a/gdk-pixbuf/pixops/pixops.c b/gdk-pixbuf/pixops/pixops.c
|
|
|
159db5 |
index b7951c7..5564a40 100644
|
|
|
159db5 |
--- a/gdk-pixbuf/pixops/pixops.c
|
|
|
159db5 |
+++ b/gdk-pixbuf/pixops/pixops.c
|
|
|
159db5 |
@@ -1272,18 +1272,17 @@ make_filter_table (PixopsFilter *filter)
|
|
|
159db5 |
int i_offset, j_offset;
|
|
|
159db5 |
int n_x = filter->x.n;
|
|
|
159db5 |
int n_y = filter->y.n;
|
|
|
159db5 |
- int n_weights;
|
|
|
159db5 |
int *weights;
|
|
|
159db5 |
|
|
|
159db5 |
- n_weights = SUBSAMPLE * SUBSAMPLE * n_x;
|
|
|
159db5 |
- if (n_weights / (SUBSAMPLE * SUBSAMPLE) != n_x)
|
|
|
159db5 |
- return NULL; /* overflow, bail */
|
|
|
159db5 |
+ /* check n_x doesn't overflow */
|
|
|
159db5 |
+ if (G_MAXINT / (SUBSAMPLE * SUBSAMPLE) < n_x)
|
|
|
159db5 |
+ return NULL;
|
|
|
159db5 |
|
|
|
159db5 |
- n_weights *= n_y;
|
|
|
159db5 |
- if (n_weights / (SUBSAMPLE * SUBSAMPLE * n_x) != n_y)
|
|
|
159db5 |
- return NULL; /* overflow, bail */
|
|
|
159db5 |
+ /* check n_y doesn't overflow */
|
|
|
159db5 |
+ if (G_MAXINT / (SUBSAMPLE * SUBSAMPLE * n_x) < n_y)
|
|
|
159db5 |
+ return NULL;
|
|
|
159db5 |
|
|
|
159db5 |
- weights = g_try_new (int, n_weights);
|
|
|
159db5 |
+ weights = g_try_new (int, SUBSAMPLE * SUBSAMPLE * n_x * n_y);
|
|
|
159db5 |
if (!weights)
|
|
|
159db5 |
return NULL; /* overflow, bail */
|
|
|
159db5 |
|
|
|
159db5 |
--
|
|
|
159db5 |
2.5.2
|
|
|
159db5 |
|