Allocate high addresses with mmap

mmap_high.c

#include <stdio.h>
#include <stdint.h>

#include <sys/mman.h>

int main(void){
    void * const hint = (void*)~(uintptr_t)0;
    const void * const reserved = mmap(hint, 1, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    printf("hint:%p\nreserved: %p\n", hint, reserved);
}