macosx specific zmalloc.c, uses malloc_size function in order to avoid to waste memory and time to put an additional header

TODO

@@ -29,7 +29,8 @@ AFTER 1.0 stable release
    side the type also takes an hash table with key->score mapping, so that when
    there is an update we lookup the current score and can traverse the tree.
  * BITMAP type
- * LRANGE 4 0 should return the same elements as LRANGE 0 4 but in reverse order
+ * LRANGE 4 0 should return the same elements as LRANGE 0 4 but in reverse order (only if we get enough motivated requests about it)
+ * zmalloc() should avoid to add a private header for archs where there is some other kind of libc-specific way to get the size of a malloced block.
 
 FUTURE HINTS
 

zmalloc.c

@@ -31,23 +31,45 @@
 #include <stdlib.h>
 #include <string.h>
 
+#ifdef __APPLE__
+#include <malloc/malloc.h>
+#define HAVE_MALLOC_SIZE
+#define redis_malloc_size(p) malloc_size(p)
+#endif
+
 static size_t used_memory = 0;
 
 void *zmalloc(size_t size) {
     void *ptr = malloc(size+sizeof(size_t));
 
     if (!ptr) return NULL;
+#ifdef HAVE_MALLOC_SIZE
+    used_memory += redis_malloc_size(ptr);
+    return ptr;
+#else
     *((size_t*)ptr) = size;
     used_memory += size+sizeof(size_t);
     return (char*)ptr+sizeof(size_t);
+#endif
 }
 
 void *zrealloc(void *ptr, size_t size) {
+#ifndef HAVE_MALLOC_SIZE
     void *realptr;
+#endif
     size_t oldsize;
     void *newptr;
 
     if (ptr == NULL) return zmalloc(size);
+#ifdef HAVE_MALLOC_SIZE
+    oldsize = redis_malloc_size(ptr);
+    newptr = realloc(ptr,size);
+    if (!newptr) return NULL;
+
+    used_memory -= oldsize;
+    used_memory += redis_malloc_size(newptr);
+    return newptr;
+#else
     realptr = (char*)ptr-sizeof(size_t);
     oldsize = *((size_t*)realptr);
     newptr = realloc(realptr,size+sizeof(size_t));
@@ -57,17 +79,25 @@ void *zrealloc(void *ptr, size_t size) {
     used_memory -= oldsize;
     used_memory += size;
     return (char*)newptr+sizeof(size_t);
+#endif
 }
 
 void zfree(void *ptr) {
+#ifndef HAVE_MALLOC_SIZE
     void *realptr;
     size_t oldsize;
+#endif
 
     if (ptr == NULL) return;
+#ifdef HAVE_MALLOC_SIZE
+    used_memory -= redis_malloc_size(ptr);
+    free(ptr);
+#else
     realptr = (char*)ptr-sizeof(size_t);
     oldsize = *((size_t*)realptr);
     used_memory -= oldsize+sizeof(size_t);
     free(realptr);
+#endif
 }
 
 char *zstrdup(const char *s) {