greatly improve freopen behavior

1. don't open /dev/null just as a basis to copy flags; use shared
__fmodeflags function to get the right file flags for the mode.

2. handle the case (probably invalid, but whatever) case where the
original stream's file descriptor was closed; previously, the logic
re-closed it.

3. accept the "e" mode flag for close-on-exec; update dup3 to fallback
to using dup2 so we can simply call __dup3 instead of putting fallback
logic in freopen itself.

diff --git a/src/internal/stdio_impl.h b/src/internal/stdio_impl.h
index 65dcfbd..279e91f 100644 (file)
--- a/src/internal/stdio_impl.h
+++ b/src/internal/stdio_impl.h
@@ -87,6 +87,7 @@ size_t __fwritex(const unsigned char *, size_t, FILE *);
 int __putc_unlocked(int, FILE *);
 
 FILE *__fdopen(int, const char *);
+int __fmodeflags(const char *);
 
 #define OFLLOCK() LOCK(libc.ofl_lock)
 #define OFLUNLOCK() UNLOCK(libc.ofl_lock)

diff --git a/src/stdio/__fmodeflags.c b/src/stdio/__fmodeflags.c
new file mode 100644 (file)
index 0000000..da9f23b
--- /dev/null
+++ b/src/stdio/__fmodeflags.c
@@ -0,0 +1,16 @@
+#include <fcntl.h>
+#include <string.h>
+
+int __fmodeflags(const char *mode)
+{
+       int flags;
+       if (strchr(mode, '+')) flags = O_RDWR;
+       else if (*mode == 'r') flags = O_RDONLY;
+       else flags = O_WRONLY;
+       if (strchr(mode, 'x')) flags |= O_EXCL;
+       if (strchr(mode, 'e')) flags |= O_CLOEXEC;
+       if (*mode != 'r') flags |= O_CREAT;
+       if (*mode == 'w') flags |= O_TRUNC;
+       if (*mode == 'a') flags |= O_APPEND;
+       return flags;
+}

diff --git a/src/stdio/fopen.c b/src/stdio/fopen.c
index 03c10cd..c741aed 100644 (file)
--- a/src/stdio/fopen.c
+++ b/src/stdio/fopen.c
@@ -13,14 +13,7 @@ FILE *fopen(const char *restrict filename, const char *restrict mode)
        }
 
        /* Compute the flags to pass to open() */
-       if (strchr(mode, '+')) flags = O_RDWR;
-       else if (*mode == 'r') flags = O_RDONLY;
-       else flags = O_WRONLY;
-       if (strchr(mode, 'x')) flags |= O_EXCL;
-       if (strchr(mode, 'e')) flags |= O_CLOEXEC;
-       if (*mode != 'r') flags |= O_CREAT;
-       if (*mode == 'w') flags |= O_TRUNC;
-       if (*mode == 'a') flags |= O_APPEND;
+       flags = __fmodeflags(mode);
 
        fd = syscall_cp(SYS_open, filename, flags|O_LARGEFILE, 0666);
        if (fd < 0) return 0;

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;

diff --git a/src/unistd/dup3.c b/src/unistd/dup3.c
index 18f6fcc..1f7134b 100644 (file)
--- a/src/unistd/dup3.c
+++ b/src/unistd/dup3.c
@@ -1,10 +1,21 @@
 #define _GNU_SOURCE
 #include <unistd.h>
 #include <errno.h>
+#include <fcntl.h>
 #include "syscall.h"
+#include "libc.h"
 
-int dup3(int old, int new, int flags) {
+int __dup3(int old, int new, int flags)
+{
        int r;
-       while ((r=__syscall(SYS_dup3, old, new, flags))==-EBUSY);
+       if (old==new) return __syscall_ret(-EINVAL);
+       if (flags & O_CLOEXEC) {
+               while ((r=__syscall(SYS_dup3, old, new, flags))==-EBUSY);
+               if (r!=-ENOSYS) return __syscall_ret(r);
+       }
+       while ((r=__syscall(SYS_dup2, old, new))==-EBUSY);
+       if (flags & O_CLOEXEC) __syscall(SYS_fcntl, new, F_SETFD, FD_CLOEXEC);
        return __syscall_ret(r);
 }
+
+weak_alias(__dup3, dup3);