libio/bug-ungetc.c

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