Use PWD in get_current_dir_name(3) if correct.

libc/Makefile

@@ -589,6 +589,7 @@ unistd/fork.o \
 unistd/fpathconf.o \
 unistd/fsync.o \
 unistd/ftruncate.o \
+unistd/get_current_dir_name.o \
 unistd/getcwd.o \
 unistd/getdomainname.o \
 unistd/getegid.o \

libc/unistd/get_current_dir_name.cpp

@@ -0,0 +1,46 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2014.
+
+    This file is part of the Sortix C Library.
+
+    The Sortix C Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or (at your
+    option) any later version.
+
+    The Sortix C Library is distributed in the hope that it will be useful, but
+    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+    License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
+
+    unistd/get_current_dir_name.cpp
+    Returns the current working directory.
+
+*******************************************************************************/
+
+#include <sys/stat.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+// TODO: This interface should removed as its $PWD use is not thread safe.
+extern "C" char* get_current_dir_name(void)
+{
+	const char* pwd = getenv("PWD");
+	int saved_errno = errno;
+	struct stat pwd_st;
+	struct stat cur_st;
+	if ( pwd && pwd[0] && stat(pwd, &pwd_st) == 0 && stat(".", &cur_st) == 0 )
+	{
+		if ( cur_st.st_dev == pwd_st.st_dev && cur_st.st_ino == pwd_st.st_ino )
+			return strdup(pwd);
+	}
+	errno = saved_errno;
+	return canonicalize_file_name(".");
+}

libc/unistd/getcwd.cpp

@@ -1,6 +1,6 @@
 /*******************************************************************************
 
-    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012.
+    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2014.
 
     This file is part of the Sortix C Library.
 
@@ -27,25 +27,19 @@
 #include <string.h>
 #include <unistd.h>
 
-extern "C" char* get_current_dir_name(void)
-{
-	return canonicalize_file_name(".");
-}
-
 extern "C" char* getcwd(char* buf, size_t size)
 {
-	char* cwd = get_current_dir_name();
-	if ( !buf )
-		return cwd;
+	char* cwd = canonicalize_file_name(".");
 	if ( !cwd )
 		return NULL;
-	if ( size < strlen(cwd) + 1 )
+	if ( !buf )
+		return cwd;
+	if ( size <= strlcpy(buf, cwd, size) )
 	{
 		free(cwd);
 		errno = ERANGE;
 		return NULL;
 	}
-	strcpy(buf, cwd);
 	free(cwd);
 	return buf;
 }