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