libio/bug-ungetc.c

   1 /* Test program for ungetc/ftell interaction bug.  */
   2
   3 #include <stdio.h>
   4
   5 #include <support/xunistd.h>
   6
   7 static void do_prepare (void);
   8 #define PREPARE(argc, argv) do_prepare ()
   9 static int do_test (void);
  10 #define TEST_FUNCTION do_test ()
  11 #include <test-skeleton.c>
  12
  13 static const char pattern[] = "12345";
  14 static char *temp_file;
  15
  16 static void
  17 do_prepare (void)
  18 {
  19   int fd = create_temp_file ("bug-ungetc.", &temp_file);
  20   if (fd == -1)
  21     {
  22       printf ("cannot create temporary file: %m\n");
  23       exit (1);
  24     }
  25   xwrite (fd, pattern, sizeof (pattern));
  26   close (fd);
  27 }
  28
  29 static int
  30 do_test (void)
  31 {
  32   int i;
  33   FILE *f;
  34   char buf[10];
  35   long offset, diff;
  36   int result = 0;
  37
  38   f = fopen (temp_file, "rw");
  39
  40   rewind (f);
  41   for (i = 0; i < 3; i++)
  42     printf ("%c\n", getc (f));
  43   offset = ftell (f);
  44   printf ("offset = %ld\n", offset);
  45   if (ungetc ('4', f) != '4')
  46     {
  47       printf ("ungetc failed\n");
  48       abort ();
  49     }
  50   printf ("offset after ungetc = %ld\n", ftell (f));
  51
  52   i = fread ((void *) buf, 4, (size_t) 1, f);
  53   printf ("read %d (%c), offset = %ld\n", i, buf[0], ftell (f));
  54   diff = ftell (f) - offset;
  55   if (diff != 3)
  56     {
  57       printf ("ftell did not update properly.  got %ld, expected 3\n", diff);
  58       result = 1;
  59     }
  60   fclose (f);
  61
  62   return result;
  63 }