1#include "stdio_impl.h" 2#include <fcntl.h> 3 4/* The basic idea of this implementation is to open a new FILE, 5 * hack the necessary parts of the new FILE into the old one, then 6 * close the new FILE. */ 7 8/* Locking IS necessary because another thread may provably hold the 9 * lock, via flockfile or otherwise, when freopen is called, and in that 10 * case, freopen cannot act until the lock is released. */ 11 12int __dup3(int, int, int); 13 14FILE *freopen(const char *restrict filename, const char *restrict mode, FILE *restrict f) 15{ 16 int fl = __fmodeflags(mode); 17 FILE *f2; 18 19 FLOCK(f); 20 21 fflush(f); 22 23 if (!filename) { 24 if (fl&O_CLOEXEC) 25 __syscall(SYS_fcntl, f->fd, F_SETFD, FD_CLOEXEC); 26 fl &= ~(O_CREAT|O_EXCL|O_CLOEXEC); 27 if (syscall(SYS_fcntl, f->fd, F_SETFL, fl) < 0) 28 goto fail; 29 } else { 30 f2 = fopen(filename, mode); 31 if (!f2) goto fail; 32 if (f2->fd == f->fd) f2->fd = -1; /* avoid closing in fclose */ 33 else if (__dup3(f2->fd, f->fd, fl&O_CLOEXEC)<0) goto fail2; 34 35 f->flags = (f->flags & F_PERM) | f2->flags; 36 f->read = f2->read; 37 f->write = f2->write; 38 f->seek = f2->seek; 39 f->close = f2->close; 40 41 fclose(f2); 42 } 43 44 FUNLOCK(f); 45 return f; 46 47fail2: 48 fclose(f2); 49fail: 50 fclose(f); 51 return NULL; 52} 53 54LFS64(freopen); 55