#include <stdio.h> __attribute__((noinline)) void big(void) { /* The below ensures the stack grows a lot. However, we hope the stack extension is not done yet, as no memory has been read/written. */ volatile char c[200000]; /* Access only the higher part of the stack, to avoid mapping SP */ /* The below 2 printfs should produce deterministic output, whatever the random value of c[]. */ if (c[200000 - 1]) fprintf(stderr, "Accessing fresh %s\n", "stack"); else fprintf(stderr, "Accessing %s stack\n", "fresh"); } int main(void ) { big(); return 0; }