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BUG: fix strict aliasing UB in MurMur hash implementation. #459

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BUG: fix strict aliasing UB in MurMur hash implementation. #459

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12 changes: 3 additions & 9 deletions src/hash.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12,15 +12,11 @@
*/

#include <stdlib.h>
#include <string.h>
#include <inttypes.h>

#include "hash.h"

static inline uint32_t getblock32(const uint32_t *p, int i)
{
return p[i];
}

static inline uint32_t rotl32(uint32_t x, int8_t r)
{
return (x << r) | (x >> (32 - r));
Expand All @@ -41,7 +37,6 @@ static inline uint32_t fmix32(uint32_t h)
uint32_t hash(const void *key, size_t length)
{
const uint8_t *data = (const uint8_t *)key;
const uint32_t *blocks;
const uint8_t *tail;
const int nblocks = length / 4;
const uint32_t c1 = 0xcc9e2d51;
Expand All @@ -54,9 +49,8 @@ uint32_t hash(const void *key, size_t length)
uint32_t h1 = 0;

/* body */
blocks = (const uint32_t *)(data + nblocks * 4);
for(i = -nblocks; i; i++) {
k1 = getblock32(blocks, i);
memcpy(&k1, data + (nblocks + i) * sizeof(uint32_t), sizeof(uint32_t));

k1 *= c1;
k1 = rotl32(k1, 15);
Expand All @@ -68,7 +62,7 @@ uint32_t hash(const void *key, size_t length)
}

/* tail */
tail = (const uint8_t *)(data + nblocks * 4);
tail = data + nblocks * sizeof(uint32_t);
switch(length & 3) {
case 3:
k2 ^= tail[2] << 16;
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