Switch to a realloc_array()-style allocator (with default implementation)

src/default_allocator.c

@@ -0,0 +1,59 @@
+/* threadless.io
+ * Copyright (c) 2016 Justin R. Cutler
+ * Licensed under the MIT License. See LICENSE file in the project root for
+ * full license information.
+ */
+/** @file
+ * default allocator implementation
+ * @author Justin R. Cutler <justin.r.cutler@gmail.com>
+ */
+/* errno, ENOMEM */
+#include <errno.h>
+/* realloc */
+#include <stdlib.h>
+
+/* ... */
+#include <threadless/allocator.h>
+
+
+#ifndef SIZE_MAX
+# define SIZE_MAX ((size_t)-1)
+#endif
+
+#define SQRT_SIZE_MAX_PLUS_1 ((size_t)1 << (sizeof(size_t) * 4))
+
+
+static void *default_allocate(allocator_t *allocator, void *ptr, size_t nmemb,
+    size_t size)
+{
+    /* ignore allocator */
+    (void) allocator;
+    /* test for multiplication overflow */
+    if (((nmemb >= SQRT_SIZE_MAX_PLUS_1) || (size >= SQRT_SIZE_MAX_PLUS_1)) &&
+        (nmemb != 0) && ((SIZE_MAX / nmemb) < size)) {
+        /* overflow detected */
+        errno = ENOMEM;
+        return NULL;
+    }
+    /* perform allocator action */
+    return realloc(ptr, size * nmemb);
+}
+
+
+static void default_destory(allocator_t *allocator)
+{
+    /* ignore allocator */
+    (void) allocator;
+}
+
+
+static allocator_t default_allocator = {
+    .allocate = default_allocate,
+    .destroy = default_destory,
+};
+
+
+allocator_t *allocator_get_default(void)
+{
+    return &default_allocator;
+}