Implement test_realloc in harness.c

Implement test_realloc() to track memory
adjustments made by realloc().
This patch enables memory allocated by test_malloc() or test_calloc()
to be adjusted using test_realloc().

Inspired by https://danluu.com/malloc-tutorial/.

Change-Id: Ic85b35cfff4dc0b6a46a6e81e6c1ce873625f0ac

Author: chensheep

harness.c

@@ -63,6 +63,7 @@ static bool time_limited = false;
 typedef enum {
     TEST_MALLOC,
     TEST_CALLOC,
+    TEST_REALLOC,
 } alloc_t;
 
 /* Internal functions */
@@ -128,6 +129,7 @@ static void *alloc(alloc_t alloc_type, size_t size)
         char *msg_alloc_forbidden[] = {
             "Calls to malloc are disallowed",
             "Calls to calloc are disallowed",
+            "Calls to realloc are disallowed",
         };
         report_event(MSG_FATAL, "%s", msg_alloc_forbidden[alloc_type]);
         return NULL;
@@ -137,6 +139,7 @@ static void *alloc(alloc_t alloc_type, size_t size)
         char *msg_alloc_failure[] = {
             "Malloc returning NULL",
             "Calloc returning NULL",
+            "Realloc returning NULL",
         };
         report_event(MSG_WARN, "%s", msg_alloc_failure[alloc_type]);
         return NULL;
@@ -187,6 +190,37 @@ void *test_calloc(size_t nelem, size_t elsize)
     return alloc(TEST_CALLOC, nelem * elsize);
 }
 
+void *test_realloc(void *p, size_t new_size)
+{
+    /*
+     * If `p` is NULL, `test_realloc()` behaves like `test_malloc()`.
+     * If `p` is not NULL, check the size of the allocated memory.
+     * If `new_size` is less than or equal to the current allocation size,
+     * update the allocated memory size to `new_size`.
+     * Otherwise, allocate new memory of size `new_size`, copy the contents
+     * from the orginal memory to the newly allocated memory,
+     * and free the original memory.
+     * Reference: Malloc tutorial
+     * https://danluu.com/malloc-tutorial/
+     */
+
+    if (!p)
+        return alloc(TEST_REALLOC, size);
+
+    const block_element_t *b = find_header(p);
+    if (b->payload_size >= size)
+        return p;
+
+    void *new_ptr;
+    new_ptr = alloc(TEST_REALLOC, size);
+    if (!new_ptr)
+        return NULL;
+    memcpy(new_ptr, p, b->payload_size);
+    test_free(p);
+
+    return new_ptr;
+}
+
 void test_free(void *p)
 {
     if (noallocate_mode) {

harness.h

@@ -12,9 +12,9 @@
 
 void *test_malloc(size_t size);
 void *test_calloc(size_t nmemb, size_t size);
+void *test_realloc(void *p, size_t new_size);
 void test_free(void *p);
 char *test_strdup(const char *s);
-/* FIXME: provide test_realloc as well */
 
 #ifdef INTERNAL
 
@@ -56,6 +56,7 @@ void trigger_exception(char *msg);
 /* Tested program use our versions of malloc and free */
 #define malloc test_malloc
 #define calloc test_calloc
+#define realloc test_realloc
 #define free test_free
 
 /* Use undef to avoid strdup redefined error */