Update fallback implementation of missing libc functions

  This commit updates realpath.c from
http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libc/stdlib/realpath.c?rev=1.14;content-type=text/plain
and lisp/env.c from
http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libc/stdlib/getenv.c?rev=1.10;content-type=text/plain
and
http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libc/stdlib/setenv.c?rev=1.13;content-type=text/plain

  The update reason is to replace files under "4 clause BSD", that
is considered problematic or require special documentation notation
or conditions when redistributing free software.

Signed-off-by: pcpa <paulo.cesar.pereira.de.andrade@gmail.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>

7 files changed, 451 insertions, 320 deletions

diff --git a/AUTHORS b/AUTHORS
index 65e5b4c..60c1d32 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -135,7 +135,7 @@ Files required for systems that don't have the required calls in the
 standard libraries:
 
 (Based on Copyright notice)
-Jan-Simon Pendry
+Constantin S. Svintsoff
 realpath.c
 
 (No author information, using CVS tag)
diff --git a/COPYING b/COPYING
index 4e83706..a2c9fab 100644
--- a/COPYING
+++ b/COPYING
@@ -1,6 +1,35 @@
+Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
+
+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. The names of the authors may not be used to endorse or promote
+   products derived from this software without specific prior written
+   permission.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
+
+
+
+
 
 Copyright (c) 1987, 1993
-     The Regents of the University of California.  All rights reserved.
+	The Regents of the University of California.  All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions
@@ -10,11 +39,7 @@ are met:
 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. All advertising materials mentioning features or use of this software
-   must display the following acknowledgement:
-     This product includes software developed by the University of
-     California, Berkeley and its contributors.
-4. Neither the name of the University nor the names of its contributors
+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.
 
@@ -34,11 +59,8 @@ SUCH DAMAGE.
 
 
 
-Copyright (c) 1994
-	The Regents of the University of California.  All rights reserved.
-
-This code is derived from software contributed to Berkeley by
-Jan-Simon Pendry.
+Copyright (c) 1987 Regents of the University of California.
+All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions
@@ -48,11 +70,7 @@ are met:
 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. All advertising materials mentioning features or use of this software
-   must display the following acknowledgement:
-	This product includes software developed by the University of
-	California, Berkeley and its contributors.
-4. Neither the name of the University nor the names of its contributors
+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.
 
diff --git a/Makefile.am b/Makefile.am
index fc7a74c..16a01d6 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -85,7 +85,8 @@ liblisp_a_SOURCES = \
 	lisp/xedit.h
 
 if NEED_UNSETENV
-liblisp_a_SOURCES += lisp/env.c
+liblisp_a_SOURCES += lisp/getenv.c
+liblisp_a_SOURCES += lisp/setenv.c
 endif
 
 #
diff --git a/lisp/env.c b/lisp/env.c
deleted file mode 100644
index e87793a..0000000
--- a/lisp/env.c
+++ /dev/null
@@ -1,151 +0,0 @@
-/*
- * Provide setenv() and unsetenv() on platforms that don't have them.
- * From FreeBSD's libc.
- */
-
-/*
- * Copyright (c) 1987, 1993
- *      The Regents of the University of California.  All rights reserved.
- *
- * 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. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *      This product includes software developed by the University of
- *      California, Berkeley and its contributors.
- * 4. 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.
- */
-
-/* $XFree86$ */
-
-
-#include <stdlib.h>
-#include <stddef.h>
-#include <string.h>
-
-extern char **environ;
-
-extern int setenv(const char *name, const char *value, int overwrite);
-extern void unsetenv(const char *name);
-
-static char *
-findenv(const char *name, int *offset)
-{
-    int len, i;
-    const char *np;
-    char **p, *cp;
-
-    if (name == NULL || environ == NULL)
-	return NULL;
-
-    for (np = name; *np && *np != '='; ++np)
-	continue;
-    len = np - name;
-    for (p = environ; (cp = *p) != NULL; ++p) {
-	for (np = name, i = len; i && *cp; i--)
-	    if (*cp++ != *np++)
-		break;
-	if (i == 0 && *cp++ == '=') {
-	    *offset = p - environ;
-	    return cp;
-	}
-    }
-    return NULL;
-}
-
-/*
- * setenv --
- *      Set the value of the environmental variable "name" to be
- *      "value".  If overwrite is set, replace any current value.
- */
-
-int
-setenv(const char *name, const char *value, int overwrite)
-{
-    static char **alloced;			/* if allocated space before */
-    char *c;
-    int l_value, offset;
-
-    if (*value == '=')				/* no '=' in value */
-	++value;
-    l_value = strlen(value);
-    if ((c = findenv(name, &offset))) {		/* find if already exists */
-	if (!overwrite)
-	    return 0;
-	if (strlen(c) >= l_value) {		/* old larger; copy over */
-	    while ((*c++ = *value++))
-		;
-	    return 0;
-	}
-    } else {					/* create new slot */
-	int cnt;
-	char **p;
-
-	for (p = environ, cnt = 0; *p; ++p, ++cnt)
-	    ;
-	if (alloced == environ) {		/* just increase size */
-	    p = (char **)realloc((char *)environ,
-				 sizeof(char *) * (cnt + 2));
-	    if (!p)
-		return -1;
-	    alloced = environ = p;
-	} else {				/* get new space */
-						/* copy old entries into it */
-	    p = malloc(sizeof(char *) * (cnt + 2));
-	    if (!p)
-		return -1;
-	    memcpy(p, environ, cnt * sizeof(char *));
-	    alloced = environ = p;
-	}
-	environ[cnt + 1] = NULL;
-	offset = cnt;
-    }
-    for (c = (char *)name; *c && *c != '='; ++c)	/* no '=' in name */
-	;
-    if (!(environ[offset] =				/* name + '=' + value */
-			malloc((int)(c - name) + l_value + 2)))
-	return -1;
-    for (c = environ[offset]; (*c = *name++) && *c != '='; ++c)
-	;
-    for (*c++ = '='; (*c++ = *value++); )
-	;
-    return 0;
-}
-
-/*
- * unsetenv(name) --
- *      Delete environmental variable "name".
- */
-
-void
-unsetenv(const char *name)
-{
-    char **p;
-    int offset;
-
-    while (findenv(name, &offset))		/* if set multiple times */
-	for (p = &environ[offset];; ++p)
-	    if (!(*p = *(p + 1)))
-		break;
-}
-
diff --git a/lisp/getenv.c b/lisp/getenv.c
new file mode 100644
index 0000000..fd8482e
--- /dev/null
+++ b/lisp/getenv.c
@@ -0,0 +1,81 @@
+/*	$OpenBSD: getenv.c,v 1.10 2010/08/23 22:31:50 millert Exp $ */
+/*
+ * Copyright (c) 1987, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * 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.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+char *__findenv(const char *name, int len, int *offset);
+
+/*
+ * __findenv --
+ *	Returns pointer to value associated with name, if any, else NULL.
+ *	Starts searching within the environmental array at offset.
+ *	Sets offset to be the offset of the name/value combination in the
+ *	environmental array, for use by putenv(3), setenv(3) and unsetenv(3).
+ *	Explicitly removes '=' in argument name.
+ *
+ *	This routine *should* be a static; don't use it.
+ */
+char *
+__findenv(const char *name, int len, int *offset)
+{
+	extern char **environ;
+	int i;
+	const char *np;
+	char **p, *cp;
+
+	if (name == NULL || environ == NULL)
+		return (NULL);
+	for (p = environ + *offset; (cp = *p) != NULL; ++p) {
+		for (np = name, i = len; i && *cp; i--)
+			if (*cp++ != *np++)
+				break;
+		if (i == 0 && *cp++ == '=') {
+			*offset = p - environ;
+			return (cp);
+		}
+	}
+	return (NULL);
+}
+
+/*
+ * getenv --
+ *	Returns ptr to value associated with name, if any, else NULL.
+ */
+char *
+getenv(const char *name)
+{
+	int offset = 0;
+	const char *np;
+
+	for (np = name; *np && *np != '='; ++np)
+		;
+	return (__findenv(name, (int)(np - name), &offset));
+}
diff --git a/lisp/setenv.c b/lisp/setenv.c
new file mode 100644
index 0000000..089ab92
--- /dev/null
+++ b/lisp/setenv.c
@@ -0,0 +1,178 @@
+/*	$OpenBSD: setenv.c,v 1.13 2010/08/23 22:31:50 millert Exp $ */
+/*
+ * Copyright (c) 1987 Regents of the University of California.
+ * All rights reserved.
+ *
+ * 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.
+ */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+char *__findenv(const char *name, int len, int *offset);
+
+extern char **environ;
+static char **lastenv;				/* last value of environ */
+
+/*
+ * putenv --
+ *	Add a name=value string directly to the environmental, replacing
+ *	any current value.
+ */
+int
+putenv(char *str)
+{
+	char **P, *cp;
+	size_t cnt;
+	int offset = 0;
+
+	for (cp = str; *cp && *cp != '='; ++cp)
+		;
+	if (*cp != '=') {
+		errno = EINVAL;
+		return (-1);			/* missing `=' in string */
+	}
+
+	if (__findenv(str, (int)(cp - str), &offset) != NULL) {
+		environ[offset++] = str;
+		/* could be set multiple times */
+		while (__findenv(str, (int)(cp - str), &offset)) {
+			for (P = &environ[offset];; ++P)
+				if (!(*P = *(P + 1)))
+					break;
+		}
+		return (0);
+	}
+
+	/* create new slot for string */
+	for (P = environ; *P != NULL; P++)
+		;
+	cnt = P - environ;
+	P = (char **)realloc(lastenv, sizeof(char *) * (cnt + 2));
+	if (!P)
+		return (-1);
+	if (lastenv != environ)
+		memcpy(P, environ, cnt * sizeof(char *));
+	lastenv = environ = P;
+	environ[cnt] = str;
+	environ[cnt + 1] = NULL;
+	return (0);
+}
+
+/*
+ * setenv --
+ *	Set the value of the environmental variable "name" to be
+ *	"value".  If rewrite is set, replace any current value.
+ */
+int
+setenv(const char *name, const char *value, int rewrite)
+{
+	char *C, **P;
+	const char *np;
+	int l_value, offset = 0;
+
+	for (np = name; *np && *np != '='; ++np)
+		;
+#ifdef notyet
+	if (*np) {
+		errno = EINVAL;
+		return (-1);			/* has `=' in name */
+	}
+#endif
+
+	l_value = strlen(value);
+	if ((C = __findenv(name, (int)(np - name), &offset)) != NULL) {
+		int tmpoff = offset + 1;
+		if (!rewrite)
+			return (0);
+#if 0 /* XXX - existing entry may not be writable */
+		if (strlen(C) >= l_value) {	/* old larger; copy over */
+			while ((*C++ = *value++))
+				;
+			return (0);
+		}
+#endif
+		/* could be set multiple times */
+		while (__findenv(name, (int)(np - name), &tmpoff)) {
+			for (P = &environ[tmpoff];; ++P)
+				if (!(*P = *(P + 1)))
+					break;
+		}
+	} else {					/* create new slot */
+		size_t cnt;
+
+		for (P = environ; *P != NULL; P++)
+			;
+		cnt = P - environ;
+		P = (char **)realloc(lastenv, sizeof(char *) * (cnt + 2));
+		if (!P)
+			return (-1);
+		if (lastenv != environ)
+			memcpy(P, environ, cnt * sizeof(char *));
+		lastenv = environ = P;
+		offset = cnt;
+		environ[cnt + 1] = NULL;
+	}
+	if (!(environ[offset] =			/* name + `=' + value */
+	    malloc((size_t)((int)(np - name) + l_value + 2))))
+		return (-1);
+	for (C = environ[offset]; (*C = *name++) && *C != '='; ++C)
+		;
+	for (*C++ = '='; (*C++ = *value++); )
+		;
+	return (0);
+}
+
+/*
+ * unsetenv(name) --
+ *	Delete environmental variable "name".
+ */
+int
+unsetenv(const char *name)
+{
+	char **P;
+	const char *np;
+	int offset = 0;
+
+	if (!name || !*name) {
+		errno = EINVAL;
+		return (-1);
+	}
+	for (np = name; *np && *np != '='; ++np)
+		;
+	if (*np) {
+		errno = EINVAL;
+		return (-1);			/* has `=' in name */
+	}
+
+	/* could be set multiple times */
+	while (__findenv(name, (int)(np - name), &offset)) {
+		for (P = &environ[offset];; ++P)
+			if (!(*P = *(P + 1)))
+				break;
+	}
+	return (0);
+}
diff --git a/realpath.c b/realpath.c
index 4d58b75..21af4cf 100644
--- a/realpath.c
+++ b/realpath.c
@@ -1,9 +1,6 @@
+/*	$OpenBSD: realpath.c,v 1.14 2011/07/24 21:03:00 miod Exp $ */
 /*
- * Copyright (c) 1994
- *	The Regents of the University of California.  All rights reserved.
- *
- * This code is derived from software contributed to Berkeley by
- * Jan-Simon Pendry.
+ * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -13,18 +10,14 @@
  * 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. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by the University of
- *	California, Berkeley and its contributors.
- * 4. 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.
+ * 3. The names of the authors may not 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
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR 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)
@@ -33,176 +26,187 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-/* $XFree86: xc/programs/xedit/realpath.c,v 1.4 2000/02/12 20:45:45 dawes Exp $ */
-
-#if defined(LIBC_SCCS) && !defined(lint)
-static char sccsid[] = "@(#)realpath.c	8.1 (Berkeley) 2/16/94";
-#endif /* LIBC_SCCS and not lint */
 
 #include <sys/param.h>
-#include <sys/types.h>
 #include <sys/stat.h>
 
 #include <errno.h>
-#include <fcntl.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
-#ifndef LISP
-#include "xedit.h"
-#endif
-
-#if defined(__Lynx__)
-#define NO_FCHDIR
-#endif
-
-#if defined(ISC)
-#ifndef MAXPATHLEN
-#define MAXPATHLEN	1024
-#endif
-#endif
-#ifndef MAXSYMLINKS
-#define MAXSYMLINKS	256
-#endif
-
 /*
- * char *realpath(const char *path, char resolved_path[MAXPATHLEN]);
+ * char *realpath(const char *path, char resolved[PATH_MAX]);
  *
  * Find the real name of path, by removing all ".", ".." and symlink
  * components.  Returns (resolved) on success, or (NULL) on failure,
  * in which case the path which caused trouble is left in (resolved).
  */
 char *
-realpath(path, resolved)
-	const char *path;
-	char *resolved;
+realpath(const char *path, char *resolved)
 {
 	struct stat sb;
-#ifdef NO_FCHDIR
-	char start[MAXPATHLEN];
-#else
-	int fd;
-#endif
-	int n, rootd, serrno;
-	char *p, *q, wbuf[MAXPATHLEN];
-	int symlinks = 0;
-
-	/* Save the starting point. */
-#ifdef NO_FCHDIR
-	if (getcwd(start, MAXPATHLEN) == NULL) {
-		(void)strcpy(resolved, ".");
-		return (NULL);
-	}
-#else
-	if ((fd = open(".", O_RDONLY)) < 0) {
-		(void)strcpy(resolved, ".");
+	char *p, *q, *s;
+	size_t left_len, resolved_len;
+	unsigned symlinks;
+	int serrno, slen, mem_allocated;
+	char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
+
+	if (path[0] == '\0') {
+		errno = ENOENT;
 		return (NULL);
 	}
-#endif
 
-	/*
-	 * Find the dirname and basename from the path to be resolved.
-	 * Change directory to the dirname component.
-	 * lstat the basename part.
-	 *     if it is a symlink, read in the value and loop.
-	 *     if it is a directory, then change to that directory.
-	 * get the current directory name and append the basename.
-	 */
-	(void)strncpy(resolved, path, MAXPATHLEN - 1);
-	resolved[MAXPATHLEN - 1] = '\0';
-loop:
-	q = strrchr(resolved, '/');
-	if (q != NULL) {
-		p = q + 1;
-		if (q == resolved)
-			q = "/";
-		else {
-			do {
-				--q;
-			} while (q > resolved && *q == '/');
-			q[1] = '\0';
-			q = resolved;
-		}
-		if (chdir(q) < 0)
-			goto err1;
-	} else
-		p = resolved;
+	serrno = errno;
 
-	/* Deal with the last component. */
-	if (*p != '\0' && lstat(p, &sb) == 0) {
-		if (S_ISLNK(sb.st_mode)) {
-                      if (++symlinks > MAXSYMLINKS) {
-                              errno = ELOOP;
-                              goto err1;
-                      }
-			n = readlink(p, resolved, MAXPATHLEN);
-			if (n < 0)
-				goto err1;
-			resolved[n] = '\0';
-			goto loop;
-		}
-		if (S_ISDIR(sb.st_mode)) {
-			if (chdir(p) < 0)
-				goto err1;
-			p = "";
+	if (resolved == NULL) {
+		resolved = malloc(PATH_MAX);
+		if (resolved == NULL)
+			return (NULL);
+		mem_allocated = 1;
+	} else
+		mem_allocated = 0;
+
+	symlinks = 0;
+	if (path[0] == '/') {
+		resolved[0] = '/';
+		resolved[1] = '\0';
+		if (path[1] == '\0')
+			return (resolved);
+		resolved_len = 1;
+		left_len = strlcpy(left, path + 1, sizeof(left));
+	} else {
+		if (getcwd(resolved, PATH_MAX) == NULL) {
+			if (mem_allocated)
+				free(resolved);
+			else
+				strlcpy(resolved, ".", PATH_MAX);
+			return (NULL);
 		}
+		resolved_len = strlen(resolved);
+		left_len = strlcpy(left, path, sizeof(left));
+	}
+	if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
+		errno = ENAMETOOLONG;
+		goto err;
 	}
 
 	/*
-	 * Save the last component name and get the full pathname of
-	 * the current directory.
-	 */
-	(void)strcpy(wbuf, p);
-	if (getcwd(resolved, MAXPATHLEN) == 0)
-		goto err1;
-
-	/*
-	 * Join the two strings together, ensuring that the right thing
-	 * happens if the last component is empty, or the dirname is root.
+	 * Iterate over path components in `left'.
 	 */
-	if (resolved[0] == '/' && resolved[1] == '\0')
-		rootd = 1;
-	else
-		rootd = 0;
-
-	if (*wbuf) {
-		if (strlen(resolved) + strlen(wbuf) + rootd + 1 > MAXPATHLEN) {
+	while (left_len != 0) {
+		/*
+		 * Extract the next path component and adjust `left'
+		 * and its length.
+		 */
+		p = strchr(left, '/');
+		s = p ? p : left + left_len;
+		if (s - left >= sizeof(next_token)) {
 			errno = ENAMETOOLONG;
-			goto err1;
+			goto err;
+		}
+		memcpy(next_token, left, s - left);
+		next_token[s - left] = '\0';
+		left_len -= s - left;
+		if (p != NULL)
+			memmove(left, s + 1, left_len + 1);
+		if (resolved[resolved_len - 1] != '/') {
+			if (resolved_len + 1 >= PATH_MAX) {
+				errno = ENAMETOOLONG;
+				goto err;
+			}
+			resolved[resolved_len++] = '/';
+			resolved[resolved_len] = '\0';
+		}
+		if (next_token[0] == '\0')
+			continue;
+		else if (strcmp(next_token, ".") == 0)
+			continue;
+		else if (strcmp(next_token, "..") == 0) {
+			/*
+			 * Strip the last path component except when we have
+			 * single "/"
+			 */
+			if (resolved_len > 1) {
+				resolved[resolved_len - 1] = '\0';
+				q = strrchr(resolved, '/') + 1;
+				*q = '\0';
+				resolved_len = q - resolved;
+			}
+			continue;
 		}
-		if (rootd == 0)
-			(void)strcat(resolved, "/");
-		(void)strcat(resolved, wbuf);
-	}
 
-	/* Go back to where we came from. */
-#ifdef NO_FCHDIR
-	if (chdir(start) < 0)
-#else
-	if (fchdir(fd) < 0)
-#endif
-	{
-		serrno = errno;
-		goto err2;
+		/*
+		 * Append the next path component and lstat() it. If
+		 * lstat() fails we still can return successfully if
+		 * there are no more path components left.
+		 */
+		resolved_len = strlcat(resolved, next_token, PATH_MAX);
+		if (resolved_len >= PATH_MAX) {
+			errno = ENAMETOOLONG;
+			goto err;
+		}
+		if (lstat(resolved, &sb) != 0) {
+			if (errno == ENOENT && p == NULL) {
+				errno = serrno;
+				return (resolved);
+			}
+			goto err;
+		}
+		if (S_ISLNK(sb.st_mode)) {
+			if (symlinks++ > MAXSYMLINKS) {
+				errno = ELOOP;
+				goto err;
+			}
+			slen = readlink(resolved, symlink, sizeof(symlink) - 1);
+			if (slen < 0)
+				goto err;
+			symlink[slen] = '\0';
+			if (symlink[0] == '/') {
+				resolved[1] = 0;
+				resolved_len = 1;
+			} else if (resolved_len > 1) {
+				/* Strip the last path component. */
+				resolved[resolved_len - 1] = '\0';
+				q = strrchr(resolved, '/') + 1;
+				*q = '\0';
+				resolved_len = q - resolved;
+			}
+
+			/*
+			 * If there are any path components left, then
+			 * append them to symlink. The result is placed
+			 * in `left'.
+			 */
+			if (p != NULL) {
+				if (symlink[slen - 1] != '/') {
+					if (slen + 1 >= sizeof(symlink)) {
+						errno = ENAMETOOLONG;
+						goto err;
+					}
+					symlink[slen] = '/';
+					symlink[slen + 1] = 0;
+				}
+				left_len = strlcat(symlink, left, sizeof(left));
+				if (left_len >= sizeof(left)) {
+					errno = ENAMETOOLONG;
+					goto err;
+				}
+			}
+			left_len = strlcpy(left, symlink, sizeof(left));
+		}
 	}
 
-	/* It's okay if the close fails, what's an fd more or less? */
-#ifndef NO_FCHDIR
-	(void)close(fd);
-#endif
+	/*
+	 * Remove trailing slash except when the resolved pathname
+	 * is a single "/".
+	 */
+	if (resolved_len > 1 && resolved[resolved_len - 1] == '/')
+		resolved[resolved_len - 1] = '\0';
 	return (resolved);
 
-err1:	serrno = errno;
-#ifdef NO_FCHDIR
-	(void)chdir(start);
-#else
-	(void)fchdir(fd);
-#endif
-err2:
-#ifndef NO_FCHDIR
-	(void)close(fd);
-#endif
-	errno = serrno;
+err:
+	if (mem_allocated)
+		free(resolved);
 	return (NULL);
 }