When possible, use system_free() to free asprintf() results.

On OS X, Ruby Enterprise Edition allocates memory with tcmalloc which is
not compatible with the system malloc. asprintf() allocates memory with
the system malloc so we need to free its result with the system free()
function instead of tcmalloc's free() function. REE's system_free()
API call does that.

Author: FooBarWidget

ext/cbson/cbson.c

@@ -162,16 +162,23 @@ static void write_utf8(buffer_t buffer, VALUE string, char check_null) {
         *buffer = malloc(vslength);             \
         _snprintf(*buffer, vslength, "%d", i);  \
     }
+#define FREE_INTSTRING(buffer) free(buffer)
 #else
 #define INT2STRING(buffer, i)                   \
     {                                           \
         int vslength = snprintf(NULL, 0, "%d", i) + 1;  \
         *buffer = malloc(vslength);             \
         snprintf(*buffer, vslength, "%d", i);   \
     }
+#define FREE_INTSTRING(buffer) free(buffer)
 #endif
 #else
 #define INT2STRING(buffer, i) asprintf(buffer, "%d", i);
+#ifdef USING_SYSTEM_ALLOCATOR_LIBRARY /* Ruby Enterprise Edition with tcmalloc */
+#define FREE_INTSTRING(buffer) system_free(buffer)
+#else
+#define FREE_INTSTRING(buffer) free(buffer)
+#endif
 #endif
 
 #ifndef RREGEXP_SRC
@@ -320,7 +327,7 @@ static int write_element(VALUE key, VALUE value, VALUE extra, int allow_id) {
                 INT2STRING(&name, i);
                 key = rb_str_new2(name);
                 write_element_with_id(key, rb_ary_entry(value, i), pack_extra(buffer, check_keys));
-                free(name);
+                FREE_INTSTRING(name);
             }
 
             // write null byte and fill in length