From 7e7f7ca3c607e2e150d63692e9cc320bbbe2e7d8 Mon Sep 17 00:00:00 2001
From: Ed Schouten <ed@FreeBSD.org>
Date: Tue, 29 Jul 2008 16:29:59 +0000
Subject: [PATCH] Convert popen()'s `pidlist' to a SLIST, for consistency.

I guess the original author of the popen() code didn't want to use our
<sys/queue.h> macro's, because the single linked list macro's didn't
offer O(1) deletion. Because I introduced SLIST_REMOVE_NEXT() some time
ago, we can now use the macro's here.

By converting the code to an SLIST, it is more consistent with other
parts of the C library and the operating system.

Reviewed by:	csjp
Approved by:	philip (mentor, implicit)
---
 lib/libc/gen/popen.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/lib/libc/gen/popen.c b/lib/libc/gen/popen.c
index 9e597b95e5d2..f3450b5e1cc4 100644
--- a/lib/libc/gen/popen.c
+++ b/lib/libc/gen/popen.c
@@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
 
 #include "namespace.h"
 #include <sys/param.h>
+#include <sys/queue.h>
 #include <sys/wait.h>
 
 #include <signal.h>
@@ -53,11 +54,12 @@ __FBSDID("$FreeBSD$");
 
 extern char **environ;
 
-static struct pid {
-	struct pid *next;
+struct pid {
+	SLIST_ENTRY(pid) next;
 	FILE *fp;
 	pid_t pid;
-} *pidlist;
+};
+static SLIST_HEAD(, pid) pidlist = SLIST_HEAD_INITIALIZER(pidlist);
 static pthread_mutex_t pidlist_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 #define	THREAD_LOCK()	if (__isthreaded) _pthread_mutex_lock(&pidlist_mutex)
@@ -133,9 +135,8 @@ popen(command, type)
 			}
 			(void)_close(pdes[1]);
 		}
-		for (p = pidlist; p; p = p->next) {
+		SLIST_FOREACH(p, &pidlist, next)
 			(void)_close(fileno(p->fp));
-		}
 		_execve(_PATH_BSHELL, argv, environ);
 		_exit(127);
 		/* NOTREACHED */
@@ -155,8 +156,7 @@ popen(command, type)
 	cur->fp = iop;
 	cur->pid = pid;
 	THREAD_LOCK();
-	cur->next = pidlist;
-	pidlist = cur;
+	SLIST_INSERT_HEAD(&pidlist, cur, next);
 	THREAD_UNLOCK();
 
 	return (iop);
@@ -171,7 +171,7 @@ int
 pclose(iop)
 	FILE *iop;
 {
-	struct pid *cur, *last;
+	struct pid *cur, *last = NULL;
 	int pstat;
 	pid_t pid;
 
@@ -179,17 +179,19 @@ pclose(iop)
 	 * Find the appropriate file pointer and remove it from the list.
 	 */
 	THREAD_LOCK();
-	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
+	SLIST_FOREACH(cur, &pidlist, next) {
 		if (cur->fp == iop)
 			break;
+		last = cur;
+	}
 	if (cur == NULL) {
 		THREAD_UNLOCK();
 		return (-1);
 	}
 	if (last == NULL)
-		pidlist = cur->next;
+		SLIST_REMOVE_HEAD(&pidlist, next);
 	else
-		last->next = cur->next;
+		SLIST_REMOVE_NEXT(&pidlist, last, next);
 	THREAD_UNLOCK();
 
 	(void)fclose(iop);