Improve popen compatibility with glibc.

* libc/posix/popen.c (popen): The 2006-08-22 change to use
FD_CLOEXEC disagrees with other implementations; instead, use
pidlist to work even when fcntl is not available.  Meanwhile,
support the 'e' modifier to set CLOEXEC, as in glibc.  Drop
cygwin-specific code, now that cygwin has its own version.
* libc/posix/Makefile.am (CHEWOUT_FILES): Document popen.
* libc/posix/posix.tex: New file.

1 files changed, 61 insertions, 14 deletions

diff --git a/newlib/libc/posix/popen.c b/newlib/libc/posix/popen.c
index d09c9c54f..accf76c98 100644
--- a/newlib/libc/posix/popen.c
+++ b/newlib/libc/posix/popen.c
@@ -32,6 +32,53 @@
  * SUCH DAMAGE.
  */
 
+/*
+FUNCTION
+<<popen>>, <<pclose>>---tie a stream to a command string
+
+INDEX
+	popen
+INDEX
+	pclose
+
+ANSI_SYNOPSIS
+	#include <stdio.h>
+	FILE *popen(char *<[s]>, char *<[mode]>);
+
+	int pclose(FILE *<[f]>);
+
+DESCRIPTION
+Use <<popen>> to create a stream to a child process executing a
+command string <<*<[s]>>> as processed by <</bin/sh>> on your system.
+The argument <[mode]> must start with either `<<r>>', where the stream
+reads from the child's <<stdout>>, or `<<w>>', where the stream writes
+to the child's <<stdin>>.  As an extension, <[mode]> may also contain
+`<<e>>' to set the close-on-exec bit of the parent's file descriptor.
+The stream created by <<popen>> must be closed by <<pclose>> to avoid
+resource leaks.
+
+Streams created by prior calls to <<popen>> are not visible in
+subsequent <<popen>> children, regardless of the close-on-exec bit.
+
+Use ``<<system(NULL)>>'' to test whether your system has <</bin/sh>>
+available.
+
+RETURNS
+<<popen>> returns a file stream opened with the specified <[mode]>,
+or <<NULL>> if a child process could not be created.  <<pclose>>
+returns -1 if the stream was not created by <<popen>> or if the
+application used <<wait>> or similar to steal the status; otherwise
+it returns the exit status of the child which can be interpreted
+in the same manner as a status obtained by <<waitpid>>.
+
+PORTABILITY
+POSIX.2 requires <<popen>> and <<pclose>>, but only specifies a mode
+of just <<r>> or <<w>>.  Where <<sh>> is found is left unspecified.
+
+Supporting OS subroutines required: <<_exit>>, <<_execve>>, <<_fork_r>>,
+<<_wait_r>>, <<pipe>>, <<fcntl>>, <<sbrk>>.
+*/
+
 #ifndef _NO_POPEN
 
 #if defined(LIBC_SCCS) && !defined(lint)
@@ -59,21 +106,21 @@ static struct pid {
 	struct pid *next;
 	FILE *fp;
 	pid_t pid;
-} *pidlist; 
-	
+} *pidlist;
+
 FILE *
 _DEFUN(popen, (program, type),
 	const char *program _AND
 	const char *type)
 {
-	struct pid *cur;
+	struct pid *cur, *last;
 	FILE *iop;
 	int pdes[2], pid;
 
        if ((*type != 'r' && *type != 'w')
 	   || (type[1]
-#ifdef __CYGWIN__
-	       && (type[2] || (type[1] != 'b' && type[1] != 't'))
+#ifdef HAVE_FCNTL
+	       && (type[2] || (type[1] != 'e'))
 #endif
 			       )) {
 		errno = EINVAL;
@@ -111,12 +158,11 @@ _DEFUN(popen, (program, type),
 			}
 			(void)close(pdes[1]);
 		}
+		/* Close all fd's created by prior popen.  */
+		for (last = NULL, cur = pidlist; cur;
+		     last = cur, cur = cur->next)
+			(void)close (fileno (cur->fp));
 		execl(_PATH_BSHELL, "sh", "-c", program, NULL);
-#ifdef __CYGWIN__
-		/* On cygwin32, we may not have /bin/sh.  In that
-                   case, try to find sh on PATH.  */
-		execlp("sh", "sh", "-c", program, NULL);
-#endif
 		_exit(127);
 		/* NOTREACHED */
 	}
@@ -131,9 +177,10 @@ _DEFUN(popen, (program, type),
 	}
 
 #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);
+	/* Mark pipe cloexec if requested.  */
+	if (type[1] == 'e')
+		fcntl (fileno (iop), F_SETFD,
+		       fcntl (fileno (iop), F_GETFD, 0) | FD_CLOEXEC);
 #endif /* HAVE_FCNTL */
 
 	/* Link into list of file descriptors. */
@@ -177,7 +224,7 @@ _DEFUN(pclose, (iop),
 	else
 		last->next = cur->next;
 	free(cur);
-		
+
 	return (pid == -1 ? -1 : pstat);
 }