[FFmpeg-cvslog] r21939 - trunk/libavcodec/bitstream.c
mru
subversion
Sun Feb 21 16:11:57 CET 2010
Author: mru
Date: Sun Feb 21 16:11:57 2010
New Revision: 21939
Log:
Avoid negative shifts in build_table()
A shift by a negative amount has undefined behaviour. Even though
the result of this shift is never used, the shift itself could
cause an exception of some kind.
Modified:
trunk/libavcodec/bitstream.c
Modified: trunk/libavcodec/bitstream.c
==============================================================================
--- trunk/libavcodec/bitstream.c Sun Feb 21 15:41:39 2010 (r21938)
+++ trunk/libavcodec/bitstream.c Sun Feb 21 16:11:57 2010 (r21939)
@@ -158,11 +158,12 @@ static int build_table(VLC *vlc, int tab
#endif
/* if code matches the prefix, it is in the table */
n -= n_prefix;
+ if (n > 0) {
if(flags & INIT_VLC_LE)
code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
else
code_prefix2= code >> n;
- if (n > 0 && code_prefix2 == code_prefix) {
+ if (code_prefix2 == code_prefix) {
if (n <= table_nb_bits) {
/* no need to add another table */
j = (code << (table_nb_bits - n)) & (table_size - 1);
@@ -196,6 +197,7 @@ static int build_table(VLC *vlc, int tab
table[j][1] = -n1; //bits
}
}
+ }
}
/* second pass : fill auxillary tables recursively */
More information about the ffmpeg-cvslog
mailing list