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Avoid undefined behavior in color table hashing.

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* image.c (CT_HASH_RGB) [COLOR_TABLE_SUPPORT]: Remove, replacing with ...
(ct_hash_rgb) [COLOR_TABLE_SUPPORT]: New function.  All uses changed.
This function avoids undefined behavior with signed shift overflow.
This commit is contained in:
Paul Eggert 2014-11-12 22:34:52 -08:00
parent 5531e676d4
commit 911ad4a15e
2 changed files with 13 additions and 2 deletions
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7
src/ChangeLog
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@ -1,3 +1,10 @@
2014-11-13 Paul Eggert <eggert@cs.ucla.edu>
Avoid undefined behavior in color table hashing.
* image.c (CT_HASH_RGB) [COLOR_TABLE_SUPPORT]: Remove, replacing with ...
(ct_hash_rgb) [COLOR_TABLE_SUPPORT]: New function. All uses changed.
This function avoids undefined behavior with signed shift overflow.
2014-11-10 Eli Zaretskii <eliz@gnu.org>
* fileio.c (Finsert_file_contents): Invalidate buffer caches also

8
src/image.c
View file

@ -4294,7 +4294,11 @@ struct ct_color
/* Value is a hash of the RGB color given by R, G, and B. */
#define CT_HASH_RGB(R, G, B) (((R) << 16) ^ ((G) << 8) ^ (B))
static unsigned
ct_hash_rgb (unsigned r, unsigned g, unsigned b)
{
return (r << 16) ^ (g << 8) ^ b;
}
/* The color hash table. */
@ -4349,7 +4353,7 @@ free_color_table (void)
static unsigned long
lookup_rgb_color (struct frame *f, int r, int g, int b)
{
unsigned hash = CT_HASH_RGB (r, g, b);
unsigned hash = ct_hash_rgb (r, g, b);
int i = hash % CT_SIZE;
struct ct_color *p;
Display_Info *dpyinfo;