diff options
Diffstat (limited to 'crc32.c')
| -rw-r--r-- | crc32.c | 12 |
1 files changed, 12 insertions, 0 deletions
@@ -237,6 +237,18 @@ unsigned long ZEXPORT crc32(crc, buf, len) #ifdef BYFOUR +/* + This BYFOUR code accesses the passed unsigned char * buffer with a 32-bit + integer pointer type. This violates the strict aliasing rule, where a + compiler can assume, for optimization purposes, that two pointers to + fundamentally different types won't ever point to the same memory. This can + manifest as a problem only if one of the pointers is written to. This code + only reads from those pointers. So long as this code remains isolated in + this compilation unit, there won't be a problem. For this reason, this code + should not be copied and pasted into a compilation unit in which other code + writes to the buffer that is passed to these routines. + */ + /* ========================================================================= */ #define DOLIT4 c ^= *buf4++; \ c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \ |