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* syscalls.cc (popen): Rewrite to accommodate situations where stdin, stdout, 

or stderr are closed.
This commit is contained in:
Christopher Faylor 2009-08-18 01:40:46 +00:00
parent 28c054b720
commit d5c44ae231
2 changed files with 79 additions and 49 deletions
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5
winsup/cygwin/ChangeLog
View File

@ -1,3 +1,8 @@
2009-08-17 Christopher Faylor <me+cygwin@cgf.cx>
* syscalls.cc (popen): Rewrite to accommodate situations where stdin,
stdout, or stderr are closed.
2009-08-17 Christopher Faylor <me+cygwin@cgf.cx>
* pipe.cc (fhandler_pipe::create_selectable): Add -pipe to default pipe names.

123
winsup/cygwin/syscalls.cc
View File

@ -3618,6 +3618,7 @@ popen (const char *command, const char *in_type)
const char *type = in_type;
char rw = *type++;
/* Sanity check in_type */
if (*type == 'b' || *type == 't')
type++;
if ((rw != 'r' && rw != 'w') || (*type != '\0'))
@ -3626,62 +3627,86 @@ popen (const char *command, const char *in_type)
return NULL;
}
int fd, other_fd, __stdin, __stdout, stdwhat;
int fds[2];
if (pipe (fds) < 0)
return NULL;
switch (rw)
int orig_fds[2] = {fds[0], fds[1]};
int myix = rw == 'r' ? 0 : 1;
int __std[2];
__std[myix] = -1; /* -1 denotes don't pass this fd to child process */
lock_process now;
FILE *fp = fdopen (fds[myix], in_type);
if (fp)
{
case 'r':
__stdin = -1;
stdwhat = 1;
other_fd = __stdout = fds[1];
fd = fds[0];
break;
case 'w':
__stdout = -1;
stdwhat = 0;
other_fd = __stdin = fds[0];
fd = fds[1];
break;
default:
return NULL; /* avoid a compiler warning */
/* If fds are in the range of stdin/stdout/stderr, move them
out of the way (possibly temporarily). Otherwise, spawn_guts
will be confused. We do this here rather than adding logic to
spawn_guts because spawn_guts is likely to be a more frequently
used routine and having stdin/stdout/stderr closed and reassigned
to pipe handles is an unlikely event. */
for (int i = 0; i < 2; i++)
if (fds[i] <= 2)
{
cygheap_fdnew newfd(3);
cygheap->fdtab.move_fd (fds[i], newfd);
fds[i] = newfd;
}
int myfd = fds[myix]; /* myfd - convenience variable for manipulation
of the "parent" end of the pipe. */
int stdchild = myix ^ 1; /* stdchild denotes the index into fd for the
handle which will be redirected to
stdin/stdout */
__std[stdchild] = fds[stdchild];
const char *argv[4] =
{
"/bin/sh",
"-c",
command,
NULL
};
/* Don't pass our end of the pipe to the child process */
int fd_state = fcntl64 (myfd, F_GETFD, 0);
fcntl64 (myfd, F_SETFD, fd_state | FD_CLOEXEC);
/* Also don't pass the file handle currently associated with stdin/stdout
to the child. This function may actually fail if the stdchild fd
is closed. But that's ok. */
int stdchild_state = fcntl64 (stdchild, F_GETFD, 0);
fcntl64 (stdchild, F_SETFD, stdchild_state | FD_CLOEXEC);
/* Start a shell process to run the given command without forking. */
pid_t pid = spawn_guts ("/bin/sh", argv, cur_environ (), _P_NOWAIT,
__std[0], __std[1]);
/* Reinstate the close-on-exec state */
fcntl64 (stdchild, F_SETFD, stdchild_state);
/* If pid >= 0 then spawn_guts succeeded. */
if (pid >= 0)
{
close (fds[stdchild]); /* Close the child end of the pipe. */
/* Move the fd back to its original slot if it has been moved since
we're always supposed to open the lowest numbered available fd
and, if fds[mix] != orig_fds[myix] then orig_fds[myix] is
presumably lower. */
if (fds[myix] != orig_fds[myix])
cygheap->fdtab.move_fd (fds[myix], myfd = orig_fds[myix]);
fhandler_pipe *fh = (fhandler_pipe *) cygheap->fdtab[myfd];
/* Flag that this handle is associated with popen and then reset
the handle's original close-on-exec state. */
fh->set_popen_pid (pid);
fcntl64 (myfd, F_SETFD, fd_state);
return fp;
}
}
FILE *fp = fdopen (fd, in_type);
fcntl64 (fd, F_SETFD, fcntl64 (fd, F_GETFD, 0) | FD_CLOEXEC);
if (!fp)
goto err;
pid_t pid;
const char *argv[4];
argv[0] = "/bin/sh";
argv[1] = "-c";
argv[2] = command;
argv[3] = NULL;
{
lock_process now;
int state = fcntl64 (stdwhat, F_GETFD, 0);
fcntl64 (stdwhat, F_SETFD, state | FD_CLOEXEC);
pid = spawn_guts ("/bin/sh", argv, cur_environ (), _P_NOWAIT,
__stdin, __stdout);
fcntl64 (stdwhat, F_SETFD, state);
}
if (pid >= 0)
{
close (other_fd);
fhandler_pipe *fh = (fhandler_pipe *) cygheap->fdtab[fd];
fh->set_popen_pid (pid);
return fp;
}
err:
/* If we reach here we've seen an error but the pipe handles are open.
Close them and return NULL. */
int save_errno = get_errno ();
close (fds[0]);
close (fds[1]);