commit 6cd4ad106ef87a3c58b0c3478e78409b47000de0
Author: Howard Chu <hyc@symas.com>
Date:   Tue Apr 25 20:17:03 2017 -0700

    Fix, errno is volatile int

diff --git a/libstdc++-v3/src/filesystem/dir.cc b/libstdc++-v3/src/filesystem/dir.cc
index 6ff12d0..5bbd664 100644
--- a/libstdc++-v3/src/filesystem/dir.cc
+++ b/libstdc++-v3/src/filesystem/dir.cc
@@ -147,7 +147,7 @@ fs::_Dir::advance(error_code* ec, directory_options options)
 
   int err = std::exchange(errno, 0);
   const auto entp = readdir(dirp);
-  std::swap(errno, err);
+  std::swap((int&)errno, err);
 
   if (entp)
     {