- int fd = fileno (f);
- if (!f || 0 > fd || fread (buffer, 1, 5, f) != 5)
- return 2;
- /* For deterministic results, ensure f read a bigger buffer. */
- if (lseek (fd, 0, SEEK_CUR) == 5)
- return 3;
- /* POSIX requires fflush-fseek to set file offset of fd. */
- if (fflush (f) != 0 || fseek (f, 0, SEEK_CUR) != 0)
- return 4;
- return !(lseek (fd, 0, SEEK_CUR) == 5);
+ int fd;
+ int c;
+ if (f == NULL)
+ return 1;
+ fd = fileno (f);
+ if (fd < 0 || fread (buffer, 1, 5, f) != 5)
+ return 2;
+ /* For deterministic results, ensure f read a bigger buffer. */
+ if (lseek (fd, 0, SEEK_CUR) == 5)
+ return 3;
+ /* POSIX requires fflush-fseek to set file offset of fd. This fails
+ on BSD systems and on mingw. */
+ if (fflush (f) != 0 || fseek (f, 0, SEEK_CUR) != 0)
+ return 4;
+ if (lseek (fd, 0, SEEK_CUR) != 5)
+ return 5;
+ /* Verify behaviour of fflush after ungetc. See
+ <http://www.opengroup.org/austin/aardvark/latest/xshbug3.txt> */
+ /* Verify behaviour of fflush after a backup ungetc. This fails on
+ mingw. */
+ c = fgetc (f);
+ ungetc (c, f);
+ fflush (f);
+ if (fgetc (f) != c)
+ return 6;
+ /* Verify behaviour of fflush after a non-backup ungetc. This fails
+ on glibc 2.8 and on BSD systems. */
+ c = fgetc (f);
+ ungetc ('@', f);
+ fflush (f);
+ if (fgetc (f) != c)
+ return 7;
+ return 0;