I don't feel like implementing a brk()/sbrk() vmm, vm_posix.c will be mmap based

include/ni_alloc/alloc.h

@@ -13,6 +13,8 @@ extern "C" {
    Design goal: easy to use in tools, easy to test, portable across Linux/macOS.
 */
 
+//#define ENABLE_NICKEL_ALLOC_SHIM
+
 typedef struct ni_alloc_stats {
     /* current usage */
     size_t bytes_in_use;       /* user-visible allocated bytes (approx if desired) */
@@ -115,6 +117,17 @@ size_t ni_align_up(size_t x, size_t align);
 */
 bool ni_alloc_validate(void);
 
+
+#ifdef ENABLE_NICKEL_ALLOC_SHIM
+   /* Allocation functions using the global allocator.
+      define symbols pointing at our versions 
+   */
+   void* malloc(size_t size) { ni_malloc(size); }
+   void  free(void* ptr) { ni_free(ptr); }
+   void* realloc(void* ptr, size_t new_size) { ni_realloc(ptr, new_size); }
+   void* calloc(size_t count, size_t elem_size) { ni_calloc(count, elem_size); }
+#endif
+
 #ifdef __cplusplus
 }
 #endif