diff -r f1e4c6dabfb4 -r 38ee262e8b94 src/allocator.c
--- a/src/allocator.c	Sun Sep 26 17:58:27 2021 +0200
+++ b/src/allocator.c	Sun Sep 26 18:01:51 2021 +0200
@@ -29,21 +29,23 @@
 #include "cx/allocator.h"
 
 #include <stdlib.h>
-#include <errno.h>
 
-void *cx_malloc_stdlib(void *unused, size_t n) {
+__attribute__((malloc))
+void *cx_malloc_stdlib(__attribute__((unused)) void *d, size_t n) {
     return malloc(n);
 }
 
-void *cx_realloc_stdlib(void *unused, void *mem, size_t n) {
+void *cx_realloc_stdlib(__attribute__((unused)) void *d, void *mem, size_t n) {
     return realloc(mem, n);
 }
 
-void *cx_calloc_stdlib(void *unused, size_t nelem, size_t n) {
+__attribute__((malloc))
+void *cx_calloc_stdlib(__attribute__((unused)) void *d, size_t nelem, size_t n) {
     return calloc(nelem, n);
 }
 
-void cx_free_stdlib(void *unused, void *mem) {
+__attribute__((nonnull))
+void cx_free_stdlib(__attribute__((unused)) void *d, void *mem) {
     free(mem);
 }
 
@@ -60,6 +62,8 @@
 };
 CxAllocator cxDefaultAllocator = &cx_default_allocator;
 
+/* IMPLEMENTATION OF HIGH LEVEL API */
+
 void *cxMalloc(CxAllocator allocator, size_t n) {
     return allocator->cl->malloc(allocator->data, n);
 }
@@ -69,10 +73,6 @@
 }
 
 int cxReallocate(CxAllocator allocator, void **mem, size_t n) {
-    if (mem == NULL) {
-        errno = EINVAL;
-        return 1;
-    }
     void* nmem = allocator->cl->realloc(allocator->data, *mem, n);
     if (nmem == NULL) {
         return 1;