Import regex from OpenBSD

Change-Id: I7ad7d907ef65e4e345f94777d730813b1270a612
diff --git a/libc/regex/regfree.c b/libc/regex/regfree.c
new file mode 100644
index 0000000..a57eba3
--- /dev/null
+++ b/libc/regex/regfree.c
@@ -0,0 +1,71 @@
+/*	$OpenBSD: regfree.c,v 1.7 2005/08/05 13:03:00 espie Exp $ */
+/*-
+ * Copyright (c) 1992, 1993, 1994 Henry Spencer.
+ * Copyright (c) 1992, 1993, 1994
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Henry Spencer.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	@(#)regfree.c	8.3 (Berkeley) 3/20/94
+ */
+
+#include <sys/types.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <regex.h>
+
+#include "utils.h"
+#include "regex2.h"
+
+/*
+ - regfree - free everything
+ */
+void
+regfree(regex_t *preg)
+{
+	struct re_guts *g;
+
+	if (preg->re_magic != MAGIC1)	/* oops */
+		return;			/* nice to complain, but hard */
+
+	g = preg->re_g;
+	if (g == NULL || g->magic != MAGIC2)	/* oops again */
+		return;
+	preg->re_magic = 0;		/* mark it invalid */
+	g->magic = 0;			/* mark it invalid */
+
+	if (g->strip != NULL)
+		free((char *)g->strip);
+	if (g->sets != NULL)
+		free((char *)g->sets);
+	if (g->setbits != NULL)
+		free((char *)g->setbits);
+	if (g->must != NULL)
+		free(g->must);
+	free((char *)g);
+}