feat: add HEDLEY_ALLOC_SIZE macro

NEWS

@@ -2,6 +2,7 @@ Version 16
 ==========
 
 * New macros:
+  * HEDLEY_ALLOC_SIZE
   * HEDLEY_DIAGNOSTIC_DISABLE_EXTRA_SEMI
   * HEDLEY_DIAGNOSTIC_DISABLE_UNSAFE_BUFFER_USAGE
 * Assorted bug fixes and enhancements.

hedley.h

@@ -1326,6 +1326,15 @@ HEDLEY_DIAGNOSTIC_PUSH
 #endif
 HEDLEY_DIAGNOSTIC_POP
 
+#if defined(HEDLEY_ALLOC_SIZE)
+#  undef HEDLEY_ALLOC_SIZE
+#endif
+#if HEDLEY_GCC_VERSION_CHECK(4,3,0) || HEDLEY_HAS_ATTRIBUTE(alloc_size)
+#  define HEDLEY_ALLOC_SIZE(...) __alloc_size__((__VA_ARGS__))
+#else
+#  define HEDLEY_ALLOC_SIZE(...)
+#endif
+
 #if defined(HEDLEY_PRINTF_FORMAT)
 #  undef HEDLEY_PRINTF_FORMAT
 #endif

test/Makefile

@@ -76,6 +76,7 @@ CXX_OUTPUT_FILE ?= --output=
 NULL =
 
 TESTS = \
+	alloc-size \
 	array-param \
 	assume \
 	cast \

test/alloc-size.c

@@ -0,0 +1,18 @@
+#include "common.h"
+
+#include <stdlib.h>
+
+HEDLEY_ALLOC_SIZE(1)
+static void*
+myalloc (size_t buffer_size) {
+  return malloc(buffer_size);
+}
+
+int main(void) {
+  void* buf = myalloc(42);
+  if (buf != NULL) {
+    free(buf);
+  }
+
+  return 0;
+}