From 0add2195f3e6a6e5209f2dfd5814e9e13fea156c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9=20Althaus?= <coding@andre4all.de>
Date: Tue, 2 Jun 2015 20:57:41 +0200
Subject: [PATCH] realloc is not a valid implementation for the wren
 reallocation function

The behavior of realloc for size == 0 is implementation defined.
It can return a non NULL pointer which must not be dereferenced but nether
the less must be freed. When calling the wren reallocation function with
size == 0 the memory pointed to ptr must be freed and NULL returned.
---
 src/vm/wren_vm.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/vm/wren_vm.c b/src/vm/wren_vm.c
index d4c81a1b..53c3edfd 100644
--- a/src/vm/wren_vm.c
+++ b/src/vm/wren_vm.c
@@ -22,9 +22,25 @@
   #include <time.h>
 #endif
 
+static void* defaultReallocate(void* ptr, size_t new_size)
+{
+  // The behavior of realloc for size == 0 is implementation defined.
+  // It can return a non NULL pointer which must not be dereferenced but nether
+  // the less must be freed. When calling the wren reallocation function with
+  // size == 0 the memory pointed to ptr must be freed and NULL returned.
+  if (ptr == NULL && new_size == 0) return NULL;
+  if (ptr != NULL && new_size == 0)
+  {
+    free(ptr);
+    return NULL;
+  }
+
+  return realloc(ptr, new_size);
+}
+
 WrenVM* wrenNewVM(WrenConfiguration* configuration)
 {
-  WrenReallocateFn reallocate = realloc;
+  WrenReallocateFn reallocate = defaultReallocate;
   if (configuration->reallocateFn != NULL)
   {
     reallocate = configuration->reallocateFn;