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greatly improve freopen behavior

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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.
This commit is contained in:
Rich Felker 2012-10-24 21:16:06 -04:00
parent 708c91f4e9
commit 892cafff66
5 changed files with 41 additions and 17 deletions
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1
src/internal/stdio_impl.h
View File

@ -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)

16
src/stdio/__fmodeflags.c Normal file
View File

@ -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;
}

9
src/stdio/fopen.c
View File

@ -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;

17
src/stdio/freopen.c
View File

@ -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;

15
src/unistd/dup3.c
View File

@ -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);