Mail Archives: cygwin/2006/08/22/15:16:11
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> Cygwin popen does not match Linux popen when stdout is closed.
...
> Oops - when stdout is closed, and the pipe is output on child, cygwin
> popen mistakenly lost the pipe in both processes.
>
>
> The real world case that found this:
> cygwin$ echo 'errprint(esyscmd(echo hi))dnl' | m4 >&-
> sh: line 0: echo: write error: Bad file descriptor
>
> linux$ echo 'errprint(esyscmd(echo hi))dnl' | m4 >&-
> hi
Fixed as follows, along with a fix to obey POSIX "The popen() function
shall ensure that any streams from previous popen() calls that remain open
in the parent process are closed in the new child process."
2006-08-22 Eric Blake <ebb9 AT byu DOT net>
* libc/posix/popen.c (popen): Don't close output end of pipe in
child if stdout was closed on entry.
[HAVE_FCNTL]: In parent, mark file as close-on-exec, per POSIX.
- --
Life is short - so eat dessert first!
Eric Blake ebb9 AT byu DOT net
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Index: libc/posix/popen.c
===================================================================
RCS file: /cvs/src/src/newlib/libc/posix/popen.c,v
retrieving revision 1.5
diff -u -p -r1.5 popen.c
--- libc/posix/popen.c 6 Jun 2003 19:57:51 -0000 1.5
+++ libc/posix/popen.c 22 Aug 2006 19:13:23 -0000
@@ -1,7 +1,7 @@
/* $NetBSD: popen.c,v 1.11 1995/06/16 07:05:33 jtc Exp $ */
/*
- * Copyright (c) 1988, 1993
+ * Copyright (c) 1988, 1993, 2006
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software written by Ken Arnold and
@@ -55,6 +55,7 @@ static char rcsid[] = "$NetBSD: popen.c,
#include <stdlib.h>
#include <string.h>
#include <paths.h>
+#include <fcntl.h>
static struct pid {
struct pid *next;
@@ -102,7 +103,9 @@ _DEFUN(popen, (program, type),
(void)dup2(pdes[1], STDOUT_FILENO);
(void)close(pdes[1]);
}
- (void) close(pdes[0]);
+ if (pdes[0] != STDOUT_FILENO) {
+ (void) close(pdes[0]);
+ }
} else {
if (pdes[0] != STDIN_FILENO) {
(void)dup2(pdes[0], STDIN_FILENO);
@@ -129,6 +132,12 @@ _DEFUN(popen, (program, type),
(void)close(pdes[0]);
}
+#ifdef HAVE_FCNTL
+ /* Hide pipe from future popens; assume fcntl can't fail. */
+ fcntl (fileno (iop), F_SETFD,
+ fcntl (fileno (iop), F_GETFD, 0) | FD_CLOEXEC);
+#endif /* HAVE_FCNTL */
+
/* Link into list of file descriptors. */
cur->fp = iop;
cur->pid = pid;
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