Fix BITPOS unaligned memory access.

src/bitops.c

@@ -104,6 +104,7 @@ long redisBitpos(void *s, unsigned long count, int bit) {
     unsigned long skipval, word = 0, one;
     long pos = 0; /* Position of bit, to return to the caller. */
     unsigned long j;
+    int found;
 
     /* Process whole words first, seeking for first word that is not
      * all ones or all zeros respectively if we are lookig for zeros
@@ -117,21 +118,27 @@ long redisBitpos(void *s, unsigned long count, int bit) {
     /* Skip initial bits not aligned to sizeof(unsigned long) byte by byte. */
     skipval = bit ? 0 : UCHAR_MAX;
     c = (unsigned char*) s;
+    found = 0;
     while((unsigned long)c & (sizeof(*l)-1) && count) {
-        if (*c != skipval) break;
+        if (*c != skipval) {
+            found = 1;
+            break;
+        }
         c++;
         count--;
         pos += 8;
     }
 
     /* Skip bits with full word step. */
-    skipval = bit ? 0 : ULONG_MAX;
     l = (unsigned long*) c;
-    while (count >= sizeof(*l)) {
-        if (*l != skipval) break;
-        l++;
-        count -= sizeof(*l);
-        pos += sizeof(*l)*8;
+    if (!found) {
+        skipval = bit ? 0 : ULONG_MAX;
+        while (count >= sizeof(*l)) {
+            if (*l != skipval) break;
+            l++;
+            count -= sizeof(*l);
+            pos += sizeof(*l)*8;
+        }
     }
 
     /* Load bytes into "word" considering the first byte as the most significant