text: #include <stdio.h>
  #include <string.h>
  #include <stdlib.h>
  
  
  static int
  do_test (void)
  {
    size_t size;
    char *buf;
    FILE *fp = open_memstream (&buf, &size);
    if (fp == NULL)
      {
        puts ("open_memstream failed");
        return 1;
      }
  
    off64_t off = ftello64 (fp);
    if (off != 0)
      {
        puts ("initial position wrong");
        return 1;
      }
  
    if (fseek (fp, 32768, SEEK_SET) != 0)
      {
        puts ("fseek failed");
        return 1;
      }
  
    if (fputs ("foo", fp) == EOF)
      {
        puts ("fputs failed");
        return 1;
      }
  
    if (fclose (fp) == EOF)
      {
        puts ("fclose failed");
        return 1;
      }
  
    if (size != 32768 + 3)
      {
        printf ("expected size %d, got %zu\n", 32768 + 3, size);
        return 1;
      }
  
    for (int i = 0; i < 32768; ++i)
      if (buf[i] != '\0')
        {
  	printf ("byte at offset %d is %#hhx\n", i, buf[i]);
  	return 1;
        }
  
    if (memcmp (buf + 32768, "foo", 3) != 0)
      {
        puts ("written string incorrect");
        return 1;
      }
  
    /* Mark the buffer.  */
    memset (buf, 'A', size);
    free (buf);
  
    /* Try again, this time with write mode enabled before the seek.  */
    fp = open_memstream (&buf, &size);
    if (fp == NULL)
      {
        puts ("2nd open_memstream failed");
        return 1;
      }
  
    off = ftello64 (fp);
    if (off != 0)
      {
        puts ("2nd initial position wrong");
        return 1;
      }
  
    if (fputs ("bar", fp) == EOF)
      {
        puts ("2nd fputs failed");
        return 1;
      }
  
    if (fseek (fp, 32768, SEEK_SET) != 0)
      {
        puts ("2nd fseek failed");
        return 1;
      }
  
    if (fputs ("foo", fp) == EOF)
      {
        puts ("3rd fputs failed");
        return 1;
      }
  
    if (fclose (fp) == EOF)
      {
        puts ("2nd fclose failed");
        return 1;
      }
  
    if (size != 32768 + 3)
      {
        printf ("2nd expected size %d, got %zu\n", 32768 + 3, size);
        return 1;
      }
  
    if (memcmp (buf, "bar", 3) != 0)
      {
        puts ("initial string incorrect in 2nd try");
        return 1;
      }
  
    for (int i = 3; i < 32768; ++i)
      if (buf[i] != '\0')
        {
  	printf ("byte at offset %d is %#hhx in 2nd try\n", i, buf[i]);
  	return 1;
        }
  
    if (memcmp (buf + 32768, "foo", 3) != 0)
      {
        puts ("written string incorrect in 2nd try");
        return 1;
      }
  
    return 0;
  }
  
  #define TEST_FUNCTION do_test ()
  #include "../test-skeleton.c"
  