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1 #include <assert.h>
2 #include <stdio.h>
3 #include <sys/syscall.h>
4 #include <sys/types.h>
5 #include <unistd.h>
6 
7 // kernel brk() and libc brk() act quite differently...
8 
main(void)9 int main(void)
10 {
11    int i;
12    void* orig_ds = sbrk(0);
13    void* ds = orig_ds;
14    void* vals[10];
15    void* res __attribute__((unused));
16 #define EOL ((void*)( ~(long)0 ))
17    vals[0] = (void*)0;
18    vals[1] = (void*)1;
19    vals[2] = ds - 0x1;          // small shrink
20    vals[3] = ds;
21    vals[4] = ds + 0x1000;       // small growth
22    vals[5] = ds + 0x40000000;   // too-big growth
23    vals[6] = ds + 0x500;        // shrink a little, but still above start size
24    vals[7] = ds - 0x1;          // shrink below start size
25 //   vals[8] = ds - 0x1000;       // shrink a lot below start size (into text)
26 //   vals[9] = EOL;
27    vals[8] = EOL;
28 
29    for (i = 0; EOL != vals[i]; i++) {
30       res = (void*)syscall(__NR_brk, vals[i]);
31    }
32 
33    assert( 0 == brk(orig_ds) );  // libc brk()
34 
35    for (i = 0; EOL != vals[i]; i++) {
36       res = (void*)(long)brk(vals[i]);
37    }
38 
39    return 0;
40 }
41