Upgrade Cwd.xs to the Cwd.xs in PathTools 3.26_01:

- abs_path() on Unix(ish) platforms has been upgraded to a much later
  version of the underlying C code from BSD. [Michael Schwern]

- If strlcpy() and strlcat() aren't available on the user's system,
  we now use ppport.h to provide them, so our C code works. [Steve
  Peters]

This unwinds change 32710 (consting from Robin Barker of the old code)

p4raw-id: //depot/perl@34606

1 files changed, 125 insertions, 113 deletions

diff --git a/ext/Cwd/Cwd.xs b/ext/Cwd/Cwd.xs
index 4864ba1179..949b94ccbf 100644
--- a/ext/Cwd/Cwd.xs
+++ b/ext/Cwd/Cwd.xs
@@ -64,148 +64,160 @@
  */
 static
 char *
-bsd_realpath(const char *path, char *resolved)
+bsd_realpath(const char *path, char resolved[MAXPATHLEN])
 {
 #ifdef VMS
        dTHX;
        return Perl_rmsexpand(aTHX_ (char*)path, resolved, NULL, 0);
 #else
-	int rootd, serrno;
-	const char *p;
-	char *q, wbuf[MAXPATHLEN];
-	int symlinks = 0;
-
-	/* Save the starting point. */
-#ifdef HAS_FCHDIR
-	int fd;
-
-	if ((fd = open(".", O_RDONLY)) < 0) {
-		(void)strcpy(resolved, ".");
+	char *p, *q, *s;
+	size_t left_len, resolved_len;
+	unsigned symlinks;
+	int serrno;
+	char left[MAXPATHLEN], next_token[MAXPATHLEN], symlink[MAXPATHLEN];
+
+	serrno = errno;
+	symlinks = 0;
+	if (path[0] == '/') {
+		resolved[0] = '/';
+		resolved[1] = '\0';
+		if (path[1] == '\0')
+			return (resolved);
+		resolved_len = 1;
+		left_len = my_strlcpy(left, path + 1, sizeof(left));
+	} else {
+		if (getcwd(resolved, MAXPATHLEN) == NULL) {
+			my_strlcpy(resolved, ".", MAXPATHLEN);
 		return (NULL);
 	}
-#else
-	char wd[MAXPATHLEN];
-
-	if (getcwd(wd, MAXPATHLEN - 1) == NULL) {
-		(void)strcpy(resolved, ".");
+		resolved_len = strlen(resolved);
+		left_len = my_strlcpy(left, path, sizeof(left));
+	}
+	if (left_len >= sizeof(left) || resolved_len >= MAXPATHLEN) {
+		errno = ENAMETOOLONG;
 		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.
+	 * Iterate over path components in `left'.
 	 */
-	(void)strncpy(resolved, path, MAXPATHLEN - 1);
-	resolved[MAXPATHLEN - 1] = '\0';
-loop:
-	q = strrchr(resolved, '/');
-	if (q != NULL) {
-		const char *dir;
-		p = q + 1;
-		if (q == resolved)
-			dir = "/";
-		else {
-			do {
-				--q;
-			} while (q > resolved && *q == '/');
-			q[1] = '\0';
-			dir = resolved;
-		}
-		if (chdir(dir) < 0)
-			goto err1;
-	} else
-		p = resolved;
-
-#if defined(HAS_LSTAT) && defined(HAS_READLINK) && defined(HAS_SYMLINK)
-    {
-	struct stat sb;
-	/* Deal with the last component. */
-	if (lstat(p, &sb) == 0) {
-		if (S_ISLNK(sb.st_mode)) {
-			int n;
-			if (++symlinks > MAXSYMLINKS) {
-				errno = ELOOP;
-				goto err1;
+	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;
+			return (NULL);
 			}
-			n = readlink(p, resolved, MAXPATHLEN-1);
-			if (n < 0)
-				goto err1;
-			resolved[n] = '\0';
-			goto loop;
-		}
-		if (S_ISDIR(sb.st_mode)) {
-			if (chdir(p) < 0)
-				goto err1;
-			p = "";
+		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 >= MAXPATHLEN) {
+				errno = ENAMETOOLONG;
+				return (NULL);
 		}
+			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;
     }
-#endif
 
 	/*
-	 * Save the last component name and get the full pathname of
-	 * the current directory.
+		 * Append the next path component and lstat() it. If
+		 * lstat() fails we still can return successfully if
+		 * there are no more path components left.
 	 */
-	(void)strcpy(wbuf, p);
-	if (getcwd(resolved, MAXPATHLEN) == 0)
-		goto err1;
+		resolved_len = my_strlcat(resolved, next_token, MAXPATHLEN);
+		if (resolved_len >= MAXPATHLEN) {
+			errno = ENAMETOOLONG;
+			return (NULL);
+		}
+	#if defined(HAS_LSTAT) && defined(HAS_READLINK) && defined(HAS_SYMLINK)
+		{
+			struct stat sb;
+			if (lstat(resolved, &sb) != 0) {
+				if (errno == ENOENT && p == NULL) {
+					errno = serrno;
+					return (resolved);
+				}
+				return (NULL);
+			}
+			if (S_ISLNK(sb.st_mode)) {
+				int slen;
+				
+				if (symlinks++ > MAXSYMLINKS) {
+					errno = ELOOP;
+					return (NULL);
+				}
+				slen = readlink(resolved, symlink, sizeof(symlink) - 1);
+				if (slen < 0)
+					return (NULL);
+				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;
+				}
 
 	/*
-	 * Join the two strings together, ensuring that the right thing
-	 * happens if the last component is empty, or the dirname is root.
+				 * If there are any path components left, then
+				 * append them to symlink. The result is placed
+				 * in `left'.
 	 */
-	if (resolved[0] == '/' && resolved[1] == '\0')
-		rootd = 1;
-	else
-		rootd = 0;
-
-	if (*wbuf) {
-		if (strlen(resolved) + strlen(wbuf) + (1 - rootd) + 1 > MAXPATHLEN) {
+				if (p != NULL) {
+					if (symlink[slen - 1] != '/') {
+						if (slen + 1 >= sizeof(symlink)) {
 			errno = ENAMETOOLONG;
-			goto err1;
+							return (NULL);
 		}
-		if (rootd == 0)
-			(void)strcat(resolved, "/");
-		(void)strcat(resolved, wbuf);
+						symlink[slen] = '/';
+						symlink[slen + 1] = 0;
 	}
-
-	/* Go back to where we came from. */
-#ifdef HAS_FCHDIR
-	if (fchdir(fd) < 0) {
-		serrno = errno;
-		goto err2;
+					left_len = my_strlcat(symlink, left, sizeof(left));
+					if (left_len >= sizeof(left)) {
+						errno = ENAMETOOLONG;
+						return (NULL);
 	}
-#else
-	if (chdir(wd) < 0) {
-		serrno = errno;
-		goto err2;
 	}
-#endif
+				left_len = my_strlcpy(left, symlink, sizeof(left));
+			}
+		}
+	#endif
+	}
 
-	/* It's okay if the close fails, what's an fd more or less? */
-#ifdef HAS_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 HAS_FCHDIR
-	(void)fchdir(fd);
-#else
-	(void)chdir(wd);
-#endif
-
-err2:
-#ifdef HAS_FCHDIR
-	(void)close(fd);
-#endif
-	errno = serrno;
-	return (NULL);
 #endif
 }