[PATCH] Make insque POSIX compliant (BZ #2766)

[Jakub Jelinek <jakub@redhat.com>]

Hi!

POSIX mandates that insque (ptr, NULL) initializes ptr's forward and
backward pointers to NULL (i.e. ptr is now part of single entry
linear doubly-linked list).

2006-06-14  Jakub Jelinek  <jakub@redhat.com>

	[BZ #2766]
	* misc/insremque.c (insque): Handle prev == NULL.
	* misc/Makefile (tests): Add tst-insremque.
	* misc/tst-insremque.c: New test.

--- libc/misc/insremque.c.jj	2001-07-06 06:55:36.000000000 +0200
+++ libc/misc/insremque.c	2006-06-14 14:02:35.000000000 +0200
@@ -1,4 +1,4 @@
-/* Copyright (C) 1992, 1995, 1996 Free Software Foundation, Inc.
+/* Copyright (C) 1992, 1995, 1996, 2006 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -24,12 +24,20 @@
 void
 insque (void *elem, void *prev)
 {
-  struct qelem *next = ((struct qelem *) prev)->q_forw;
-  ((struct qelem *) prev)->q_forw = (struct qelem *) elem;
-  if (next != NULL)
-    next->q_back = (struct qelem *) elem;
-  ((struct qelem *) elem)->q_forw = next;
-  ((struct qelem *) elem)->q_back = (struct qelem *) prev;
+  if (prev == NULL)
+    {
+      ((struct qelem *) elem)->q_forw = NULL;
+      ((struct qelem *) elem)->q_back = NULL;
+    }
+  else
+    {
+      struct qelem *next = ((struct qelem *) prev)->q_forw;
+      ((struct qelem *) prev)->q_forw = (struct qelem *) elem;
+      if (next != NULL)
+	next->q_back = (struct qelem *) elem;
+      ((struct qelem *) elem)->q_forw = next;
+      ((struct qelem *) elem)->q_back = (struct qelem *) prev;
+    }
 }
 
 /* Unlink ELEM from the doubly-linked list that it is in.  */
--- libc/misc/Makefile.jj	2006-02-24 10:58:23.000000000 +0100
+++ libc/misc/Makefile	2006-06-14 14:23:50.000000000 +0200
@@ -78,7 +78,7 @@ endif
 gpl2lgpl := error.c error.h
 
 tests := tst-dirname tst-tsearch tst-fdset tst-efgcvt tst-mntent tst-hsearch \
-	 tst-error1 tst-pselect
+	 tst-error1 tst-pselect tst-insremque
 ifeq (no,$(cross-compiling))
 tests: $(objpfx)tst-error1-mem
 endif
--- libc/misc/tst-insremque.c.jj	2006-06-14 14:29:18.000000000 +0200
+++ libc/misc/tst-insremque.c	2006-06-14 14:23:22.000000000 +0200
@@ -0,0 +1,61 @@
+#include <search.h>
+#include <stdio.h>
+#include <string.h>
+
+#define CHECK(cond) \
+  do									\
+    if (! (cond))							\
+      {									\
+	printf ("Condition " #cond " not true on line %d\n", __LINE__);	\
+	ret = 1;							\
+      }									\
+  while (0)
+
+static int
+do_test (void)
+{
+  struct qelem elements[4];
+  int ret = 0;
+
+  /* Linear list.  */
+  memset (elements, 0xff, sizeof (elements));
+  insque (&elements[0], NULL);
+  remque (&elements[0]);
+  insque (&elements[0], NULL);
+  insque (&elements[2], &elements[0]);
+  insque (&elements[1], &elements[0]);
+  insque (&elements[3], &elements[2]);
+  remque (&elements[2]);
+  insque (&elements[2], &elements[0]);
+  CHECK (elements[0].q_back == NULL);
+  CHECK (elements[0].q_forw == &elements[2]);
+  CHECK (elements[1].q_back == &elements[2]);
+  CHECK (elements[1].q_forw == &elements[3]);
+  CHECK (elements[2].q_back == &elements[0]);
+  CHECK (elements[2].q_forw == &elements[1]);
+  CHECK (elements[3].q_back == &elements[1]);
+  CHECK (elements[3].q_forw == NULL);
+
+  /* Circular list.  */
+  memset (elements, 0xff, sizeof (elements));
+  elements[0].q_back = &elements[0];
+  elements[0].q_forw = &elements[0];
+  insque (&elements[2], &elements[0]);
+  insque (&elements[1], &elements[0]);
+  insque (&elements[3], &elements[2]);
+  remque (&elements[2]);
+  insque (&elements[2], &elements[0]);
+  CHECK (elements[0].q_back == &elements[3]);
+  CHECK (elements[0].q_forw == &elements[2]);
+  CHECK (elements[1].q_back == &elements[2]);
+  CHECK (elements[1].q_forw == &elements[3]);
+  CHECK (elements[2].q_back == &elements[0]);
+  CHECK (elements[2].q_forw == &elements[1]);
+  CHECK (elements[3].q_back == &elements[1]);
+  CHECK (elements[3].q_forw == &elements[0]);
+
+  return ret;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"

	Jakub