1#include <stdio.h>
2#include <string.h>
3
4char x[4096], z[4096], b[21], m[4096 * 4];
5
6int
7main (void)
8{
9 FILE *f = tmpfile ();
10 int i, failed = 0;
11
12 memset (x, 'x', 4096);
13 memset (z, 'z', 4096);
14 b[20] = 0;
15
16 for (i = 0; i <= 5; i++)
17 {
18 fwrite (x, 4096, 1, f);
19 fwrite (z, 4096, 1, f);
20 }
21 rewind (f);
22
23 fread (ptr: m, size: 4096 * 4 - 10, n: 1, stream: f);
24 fread (ptr: b, size: 20, n: 1, stream: f);
25 printf (format: "got %s (should be %s)\n", b, "zzzzzzzzzzxxxxxxxxxx");
26 if (strcmp (b, "zzzzzzzzzzxxxxxxxxxx"))
27 failed = 1;
28
29 fseek (f, -40, SEEK_CUR);
30 fread (ptr: b, size: 20, n: 1, stream: f);
31 printf (format: "got %s (should be %s)\n", b, "zzzzzzzzzzzzzzzzzzzz");
32 if (strcmp (b, "zzzzzzzzzzzzzzzzzzzz"))
33 failed = 1;
34
35 fread (ptr: b, size: 20, n: 1, stream: f);
36 printf (format: "got %s (should be %s)\n", b, "zzzzzzzzzzxxxxxxxxxx");
37 if (strcmp (b, "zzzzzzzzzzxxxxxxxxxx"))
38 failed = 1;
39
40 fread (ptr: b, size: 20, n: 1, stream: f);
41 printf (format: "got %s (should be %s)\n", b, "xxxxxxxxxxxxxxxxxxxx");
42 if (strcmp (b, "xxxxxxxxxxxxxxxxxxxx"))
43 failed = 1;
44
45 return failed;
46}
47

source code of glibc/stdio-common/bug12.c