diff options
Diffstat (limited to 'src/stdio/freopen.c')
| -rw-r--r-- | src/stdio/freopen.c | 24 |
1 files changed, 14 insertions, 10 deletions
diff --git a/src/stdio/freopen.c b/src/stdio/freopen.c index c80ce3b4..7ae116d8 100644 --- a/src/stdio/freopen.c +++ b/src/stdio/freopen.c @@ -4,8 +4,9 @@ * hack the necessary parts of the new FILE into the old one, then * close the new FILE. */ -/* Locking is not necessary because, in the event of failure, the stream - * passed to freopen is invalid as soon as freopen is called. */ +/* Locking IS necessary because another thread may provably hold the + * lock, via flockfile or otherwise, when freopen is called, and in that + * case, freopen cannot act until the lock is released. */ int __dup3(int, int, int); @@ -14,6 +15,8 @@ FILE *freopen(const char *restrict filename, const char *restrict mode, FILE *re int fl = __fmodeflags(mode); FILE *f2; + FLOCK(f); + fflush(f); if (!filename) { @@ -22,21 +25,22 @@ FILE *freopen(const char *restrict filename, const char *restrict mode, FILE *re fl &= ~(O_CREAT|O_EXCL|O_CLOEXEC); if (syscall(SYS_fcntl, f->fd, F_SETFL, fl) < 0) goto fail; - return f; } else { f2 = fopen(filename, mode); if (!f2) goto fail; if (f2->fd == f->fd) f2->fd = -1; /* avoid closing in fclose */ else if (__dup3(f2->fd, f->fd, fl&O_CLOEXEC)<0) goto fail2; - } - f->flags = (f->flags & F_PERM) | f2->flags; - f->read = f2->read; - f->write = f2->write; - f->seek = f2->seek; - f->close = f2->close; + f->flags = (f->flags & F_PERM) | f2->flags; + f->read = f2->read; + f->write = f2->write; + f->seek = f2->seek; + f->close = f2->close; - fclose(f2); + fclose(f2); + } + + FUNLOCK(f); return f; fail2: |