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#include <assert.h>
#include <stdio.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
// kernel brk() and libc brk() act quite differently...
int main(void)
{
int i;
void* orig_ds = sbrk(0);
void* ds = orig_ds;
void* vals[10];
void* res __attribute__((unused));
#define EOL ((void*)( ~(long)0 ))
vals[0] = (void*)0;
vals[1] = (void*)1;
vals[2] = ds - 0x1; // small shrink
vals[3] = ds;
vals[4] = ds + 0x1000; // small growth
vals[5] = ds + 0x40000000; // too-big growth
vals[6] = ds + 0x500; // shrink a little, but still above start size
vals[7] = ds - 0x1; // shrink below start size
// vals[8] = ds - 0x1000; // shrink a lot below start size (into text)
// vals[9] = EOL;
vals[8] = EOL;
for (i = 0; EOL != vals[i]; i++) {
res = (void*)syscall(__NR_brk, vals[i]);
}
assert( 0 == brk(orig_ds) ); // libc brk()
for (i = 0; EOL != vals[i]; i++) {
res = (void*)(long)brk(vals[i]);
}
return 0;
}
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