minor bug fix

assignment3/malloclab-handout/mm.c

@@ -135,6 +135,10 @@ void mm_free(void *ptr)
  */
 void *mm_realloc(void *ptr, size_t size)
 {   
+    if(size<=0){
+        mm_free(ptr);
+        return NULL;
+    }
     void *oldptr = ptr;
     struct mm_block *blockPtr = (struct mm_block*)((char *)oldptr - SIZE_T_SIZE);
     void *newptr;
@@ -150,8 +154,8 @@ void *mm_realloc(void *ptr, size_t size)
             newptr = blockPtr + ALIGN(blockPtr->size + SIZE_T_SIZE);
             *(struct mm_block *)newptr = newBlock;
             freeList[freeListSize++] = (struct mm_block *)newptr;
-            return oldptr;
         }
+        return oldptr;
     }
     newptr = mm_malloc(size);
     if (newptr == NULL)