popen: fix cygwin 1.5 bug when stdin closed

* doc/posix-functions/popen.texi (popen): Document cygwin bugs.
* modules/popen: New file.
* modules/popen-tests: Likewise.
* tests/test-popen.c: Likewise.
* m4/popen.m4: Likewise.
* lib/popen.c: Likewise.
* lib/stdio.in.h (popen): New declaration.
* m4/stdio_h.m4 (gl_STDIO_H_DEFAULTS): Add popen.
* modules/stdio (Makefile.am): Likewise.
* MODULES.html.sh (systems lacking POSIX:2008): Mention it.

Signed-off-by: Eric Blake <ebb9@byu.net>

1 files changed, 81 insertions, 0 deletions

diff --git a/lib/popen.c b/lib/popen.c
new file mode 100644
index 0000000000..a1f1d45bfd
--- /dev/null
+++ b/lib/popen.c
@@ -0,0 +1,81 @@
+/* Open a stream to a sub-process.
+   Copyright (C) 2009 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Eric Blake <ebb9@byu.net>, 2009.  */
+
+#include <config.h>
+
+/* Get the original definition of popen.  It might be defined as a macro.  */
+#define __need_FILE
+# include <stdio.h>
+#undef __need_FILE
+
+static inline FILE *
+orig_popen (const char *filename, const char *mode)
+{
+  return popen (filename, mode);
+}
+
+/* Specification.  */
+#include <stdio.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+FILE *
+rpl_popen (const char *filename, const char *mode)
+{
+  /* The mingw popen works fine, and all other platforms have fcntl.
+     The bug of the child clobbering its own file descriptors if stdin
+     or stdout was closed in the parent can be worked around by
+     opening those two fds as close-on-exec to begin with.  */
+  /* Cygwin 1.5.x also has a bug where the popen fd is improperly
+     marked close-on-exec, and if the application undoes this, then
+     the fd leaks into subsequent popen calls.  We could work around
+     this by maintaining a list of all fd's opened by popen, and
+     temporarily marking them cloexec around the real popen call, but
+     we would also have to override pclose, and the bookkeepping seems
+     extreme given that cygwin 1.7 no longer has the bug.  */
+  FILE *result;
+  int cloexec0 = fcntl (STDIN_FILENO, F_GETFD);
+  int cloexec1 = fcntl (STDOUT_FILENO, F_GETFD);
+  int saved_errno;
+
+  if (cloexec0 < 0)
+    {
+      if (open ("/dev/null", O_RDONLY) != STDIN_FILENO
+	  || fcntl (STDIN_FILENO, F_SETFD,
+		    fcntl (STDIN_FILENO, F_GETFD) | FD_CLOEXEC) == -1)
+	abort ();
+    }
+  if (cloexec1 < 0)
+    {
+      if (open ("/dev/null", O_RDONLY) != STDOUT_FILENO
+	  || fcntl (STDOUT_FILENO, F_SETFD,
+		    fcntl (STDOUT_FILENO, F_GETFD) | FD_CLOEXEC) == -1)
+	abort ();
+    }
+  result = orig_popen (filename, mode);
+  saved_errno = errno;
+  if (cloexec0 < 0)
+    close (STDIN_FILENO);
+  if (cloexec1 < 0)
+    close (STDOUT_FILENO);
+  errno = saved_errno;
+  return result;
+}