implement and use portable implementation of canonical file paths, see #909, this time against dev branch

Util/BoostFileSystemFix.h

@@ -35,8 +35,54 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #if BOOST_FILESYSTEM_VERSION < 3
 #warning Boost Installation with Filesystem3 missing, activating workaround
 #include <cstdio>
+#endif
+
+
 namespace boost {
 namespace filesystem {
+
+// adapted from: http://stackoverflow.com/questions/1746136/how-do-i-normalize-a-pathname-using-boostfilesystem
+inline boost::filesystem::path portable_canonical(
+    const boost::filesystem::path & relative_path,
+    const boost::filesystem::path & current_path = boost::filesystem::current_path())
+{
+    const boost::filesystem::path absolute_path = boost::filesystem::absolute(
+        relative_path,
+        current_path
+    );
+
+    boost::filesystem::path canonical_path;
+    for(
+        boost::filesystem::path::const_iterator path_iterator = absolute_path.begin();
+        path_iterator!=absolute_path.end();
+        ++path_iterator
+    ) {
+        if( ".." == path_iterator->string() ) {
+            // /a/b/.. is not necessarily /a if b is a symbolic link
+            if( boost::filesystem::is_symlink(canonical_path) ) {
+                canonical_path /= *path_iterator;
+            } else if( ".." == canonical_path.filename() ) {
+                // /a/b/../.. is not /a/b/.. under most circumstances
+                // We can end up with ..s in our result because of symbolic links
+                canonical_path /= *path_iterator;
+            } else {
+                // Otherwise it should be safe to resolve the parent
+                canonical_path = canonical_path.parent_path();
+            }
+        } else if( "." == path_iterator->string() ) {
+            // Ignore
+        } else {
+            // Just cat other path entries
+            canonical_path /= *path_iterator;
+        }
+    }
+    BOOST_ASSERT( canonical_path.is_absolute() );
+    BOOST_ASSERT( boost::filesystem::exists( canonical_path ) );
+    return canonical_path;
+}
+
+#if BOOST_FILESYSTEM_VERSION < 3
+
 inline path temp_directory_path() {
 	char * buffer;
 	buffer = tmpnam (NULL);
@@ -48,10 +94,9 @@ inline path unique_path(const path&) {
 	return temp_directory_path();
 }
 
-}
-}
-
 #endif
+}
+}
 
 #ifndef BOOST_FILESYSTEM_VERSION
 #define BOOST_FILESYSTEM_VERSION 3