Allow users to replace allocator and handle OOM everywhere. (#800)

* Adds an indirection to every allocation/deallocation to allow users to 
  plug in ones of their choosing (use custom functions, jemalloc, etc).

* Gracefully handle OOM everywhere in hiredis.  This should make it possible
  for users of the library to have more flexibility in how they handle such situations.

* Changes `redisReaderTask->elements` from an `int` to a `long long` to prevent
  a possible overflow when transferring the task elements into a `redisReply`.

* Adds a configurable `max elements` member to `redisReader` that defaults to
  2^32 - 1.  This can be set to "unlimited" by setting the value to zero.

1 files changed, 2 insertions, 4 deletions

diff --git a/sds.c b/sds.c
index e8b996a..f7811a7 100644
--- a/sds.c
+++ b/sds.c
@@ -30,6 +30,7 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include "fmacros.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -219,10 +220,7 @@ sds sdsMakeRoomFor(sds s, size_t addlen) {
     hdrlen = sdsHdrSize(type);
     if (oldtype==type) {
         newsh = s_realloc(sh, hdrlen+newlen+1);
-        if (newsh == NULL) {
-            s_free(sh);
-            return NULL;
-        }
+        if (newsh == NULL) return NULL;
         s = (char*)newsh+hdrlen;
     } else {
         /* Since the header size changes, need to move the string forward,