greatly improve freopen behavior

[musl] / src / stdio / freopen.c

diff --git a/src/stdio/freopen.c b/src/stdio/freopen.c
index 5b4f126..c80ce3b 100644 (file)
--- a/src/stdio/freopen.c
+++ b/src/stdio/freopen.c
@@ -7,24 +7,27 @@
 /* Locking is not necessary because, in the event of failure, the stream
  * passed to freopen is invalid as soon as freopen is called. */
 
+int __dup3(int, int, int);
+
 FILE *freopen(const char *restrict filename, const char *restrict mode, FILE *restrict f)
 {
-       int fl;
+       int fl = __fmodeflags(mode);
        FILE *f2;
 
        fflush(f);
 
        if (!filename) {
-               f2 = fopen("/dev/null", mode);
-               if (!f2) goto fail;
-               fl = __syscall(SYS_fcntl, f2->fd, F_GETFL, 0);
+               if (fl&O_CLOEXEC)
+                       __syscall(SYS_fcntl, f->fd, F_SETFD, FD_CLOEXEC);
+               fl &= ~(O_CREAT|O_EXCL|O_CLOEXEC);
                if (syscall(SYS_fcntl, f->fd, F_SETFL, fl) < 0)
-                       goto fail2;
+                       goto fail;
+               return f;
        } else {
                f2 = fopen(filename, mode);
                if (!f2) goto fail;
-               if (syscall(SYS_dup2, f2->fd, f->fd) < 0)
-                       goto fail2;
+               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;