| From dd4b061c27dc0865c8f8987d294de6e04b321c18 Mon Sep 17 00:00:00 2001 |
| From: Benjamin Otte <otte@redhat.com> |
| Date: Sat, 22 Aug 2015 23:06:23 +0200 |
| Subject: [PATCH] pixops: Be smarter than gcc's optimizer |
| |
| gcc realizes that the overflow checks aren't necessary. Why not? |
| |
| Well, if an int overflows, the behavior is undefined. And turning on |
| -fomit-instructions is valid behavior in an undefined situation. |
| --- |
| gdk-pixbuf/pixops/pixops.c | 15 +++++++-------- |
| 1 file changed, 7 insertions(+), 8 deletions(-) |
| |
| diff --git a/gdk-pixbuf/pixops/pixops.c b/gdk-pixbuf/pixops/pixops.c |
| index b7951c7..5564a40 100644 |
| --- a/gdk-pixbuf/pixops/pixops.c |
| +++ b/gdk-pixbuf/pixops/pixops.c |
| @@ -1272,18 +1272,17 @@ make_filter_table (PixopsFilter *filter) |
| int i_offset, j_offset; |
| int n_x = filter->x.n; |
| int n_y = filter->y.n; |
| - int n_weights; |
| int *weights; |
| |
| - n_weights = SUBSAMPLE * SUBSAMPLE * n_x; |
| - if (n_weights / (SUBSAMPLE * SUBSAMPLE) != n_x) |
| - return NULL; /* overflow, bail */ |
| + /* check n_x doesn't overflow */ |
| + if (G_MAXINT / (SUBSAMPLE * SUBSAMPLE) < n_x) |
| + return NULL; |
| |
| - n_weights *= n_y; |
| - if (n_weights / (SUBSAMPLE * SUBSAMPLE * n_x) != n_y) |
| - return NULL; /* overflow, bail */ |
| + /* check n_y doesn't overflow */ |
| + if (G_MAXINT / (SUBSAMPLE * SUBSAMPLE * n_x) < n_y) |
| + return NULL; |
| |
| - weights = g_try_new (int, n_weights); |
| + weights = g_try_new (int, SUBSAMPLE * SUBSAMPLE * n_x * n_y); |
| if (!weights) |
| return NULL; /* overflow, bail */ |
| |
| -- |
| 2.5.1 |
| |