diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1458,6 +1458,13 @@
 # define _LIBCPP_INIT_PRIORITY_MAX
 #endif
 
+#if defined(__GNUC__) || defined(__clang__)
+#define _LIBCPP_FORMAT_PRINTF(a, b)                                            \
+  __attribute__((__format__(__printf__, a, b)))
+#else
+#define _LIBCPP_FORMAT_PRINTF(a, b)
+#endif
+
 #endif // __cplusplus
 
 #endif // _LIBCPP_CONFIG
diff --git a/libcxx/src/filesystem/directory_iterator.cpp b/libcxx/src/filesystem/directory_iterator.cpp
--- a/libcxx/src/filesystem/directory_iterator.cpp
+++ b/libcxx/src/filesystem/directory_iterator.cpp
@@ -273,7 +273,7 @@
     path root = move(__imp_->__root_);
     __imp_.reset();
     if (m_ec)
-      err.report(m_ec, "at root \"%s\"", root);
+      err.report(m_ec, "at root " PATH_CSTR_FMT, root.c_str());
   }
   return *this;
 }
@@ -360,7 +360,7 @@
   if (m_ec) {
     path root = move(stack.top().__root_);
     __imp_.reset();
-    err.report(m_ec, "at root \"%s\"", root);
+    err.report(m_ec, "at root " PATH_CSTR_FMT, root.c_str());
   } else {
     __imp_.reset();
   }
@@ -405,7 +405,8 @@
     } else {
       path at_ent = move(curr_it.__entry_.__p_);
       __imp_.reset();
-      err.report(m_ec, "attempting recursion into \"%s\"", at_ent);
+      err.report(m_ec, "attempting recursion into " PATH_CSTR_FMT,
+                 at_ent.c_str());
     }
   }
   return false;
diff --git a/libcxx/src/filesystem/filesystem_common.h b/libcxx/src/filesystem/filesystem_common.h
--- a/libcxx/src/filesystem/filesystem_common.h
+++ b/libcxx/src/filesystem/filesystem_common.h
@@ -42,8 +42,10 @@
 
 #if defined(_LIBCPP_WIN32API)
 #define PS(x) (L##x)
+#define PATH_CSTR_FMT "\"%ls\""
 #else
 #define PS(x) (x)
+#define PATH_CSTR_FMT "\"%s\""
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
@@ -57,68 +59,47 @@
 
 namespace {
 
-static string format_string_imp(const char* msg, ...) {
-  // we might need a second shot at this, so pre-emptivly make a copy
-  struct GuardVAList {
-    va_list& target;
-    bool active = true;
-    GuardVAList(va_list& tgt) : target(tgt), active(true) {}
-    void clear() {
-      if (active)
-        va_end(target);
-      active = false;
-    }
-    ~GuardVAList() {
-      if (active)
-        va_end(target);
-    }
-  };
-  va_list args;
-  va_start(args, msg);
-  GuardVAList args_guard(args);
-
-  va_list args_cp;
-  va_copy(args_cp, args);
-  GuardVAList args_copy_guard(args_cp);
-
-  std::string result;
-
-  array<char, 256> local_buff;
-  size_t size_with_null = local_buff.size();
-  auto ret = ::vsnprintf(local_buff.data(), size_with_null, msg, args_cp);
-
-  args_copy_guard.clear();
-
-  // handle empty expansion
-  if (ret == 0)
-    return result;
-  if (static_cast<size_t>(ret) < size_with_null) {
-    result.assign(local_buff.data(), static_cast<size_t>(ret));
-    return result;
+static _LIBCPP_FORMAT_PRINTF(1, 0) string
+format_string_impl(const char* msg, va_list ap) {
+  array<char, 256> buf;
+
+  va_list apcopy;
+  va_copy(apcopy, ap);
+  int ret = ::vsnprintf(buf.data(), buf.size(), msg, apcopy);
+  va_end(apcopy);
+
+  string result;
+  if (static_cast<size_t>(ret) < buf.size()) {
+    result.assign(buf.data(), static_cast<size_t>(ret));
+  } else {
+    // we did not provide a long enough buffer on our first attempt. The
+    // return value is the number of bytes (excluding the null byte) that are
+    // needed for formatting.
+    size_t size_with_null = static_cast<size_t>(ret) + 1;
+    result.__resize_default_init(size_with_null - 1);
+    ret = ::vsnprintf(&result[0], size_with_null, msg, ap);
+    _LIBCPP_ASSERT(static_cast<size_t>(ret) == (size_with_null - 1), "TODO");
   }
-
-  // we did not provide a long enough buffer on our first attempt. The
-  // return value is the number of bytes (excluding the null byte) that are
-  // needed for formatting.
-  size_with_null = static_cast<size_t>(ret) + 1;
-  result.__resize_default_init(size_with_null - 1);
-  ret = ::vsnprintf(&result[0], size_with_null, msg, args);
-  _LIBCPP_ASSERT(static_cast<size_t>(ret) == (size_with_null - 1), "TODO");
-
   return result;
 }
 
-const path::value_type* unwrap(path::string_type const& s) { return s.c_str(); }
-const path::value_type* unwrap(path const& p) { return p.native().c_str(); }
-template <class Arg>
-Arg const& unwrap(Arg const& a) {
-  static_assert(!is_class<Arg>::value, "cannot pass class here");
-  return a;
-}
-
-template <class... Args>
-string format_string(const char* fmt, Args const&... args) {
-  return format_string_imp(fmt, unwrap(args)...);
+static _LIBCPP_FORMAT_PRINTF(1, 2) string
+format_string(const char* msg, ...) {
+  string ret;
+  va_list ap;
+  va_start(ap, msg);
+#ifndef _LIBCPP_NO_EXCEPTIONS
+  try {
+#endif  // _LIBCPP_NO_EXCEPTIONS
+    ret = format_string_impl(msg, ap);
+#ifndef _LIBCPP_NO_EXCEPTIONS
+  } catch (...) {
+    va_end(ap);
+    throw;
+  }
+#endif  // _LIBCPP_NO_EXCEPTIONS
+  va_end(ap);
+  return ret;
 }
 
 error_code capture_errno() {
@@ -190,14 +171,14 @@
     _LIBCPP_UNREACHABLE();
   }
 
-  template <class... Args>
-  T report(const error_code& ec, const char* msg, Args const&... args) const {
+  _LIBCPP_FORMAT_PRINTF(3, 0)
+  void report_impl(const error_code& ec, const char* msg, va_list ap) const {
     if (ec_) {
       *ec_ = ec;
-      return error_value<T>();
+      return;
     }
     string what =
-        string("in ") + func_name_ + ": " + format_string(msg, args...);
+        string("in ") + func_name_ + ": " + format_string_impl(msg, ap);
     switch (bool(p1_) + bool(p2_)) {
     case 0:
       __throw_filesystem_error(what, ec);
@@ -209,11 +190,44 @@
     _LIBCPP_UNREACHABLE();
   }
 
-  T report(errc const& err) const { return report(make_error_code(err)); }
+  _LIBCPP_FORMAT_PRINTF(3, 4)
+  T report(const error_code& ec, const char* msg, ...) const {
+    va_list ap;
+    va_start(ap, msg);
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try {
+#endif  // _LIBCPP_NO_EXCEPTIONS
+      report_impl(ec, msg, ap);
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    } catch (...) {
+      va_end(ap);
+      throw;
+    }
+#endif  // _LIBCPP_NO_EXCEPTIONS
+    va_end(ap);
+    return error_value<T>();
+  }
+
+  T report(errc const& err) const {
+    return report(make_error_code(err));
+  }
 
-  template <class... Args>
-  T report(errc const& err, const char* msg, Args const&... args) const {
-    return report(make_error_code(err), msg, args...);
+  _LIBCPP_FORMAT_PRINTF(3, 4)
+  T report(errc const& err, const char* msg, ...) const {
+    va_list ap;
+    va_start(ap, msg);
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try {
+#endif  // _LIBCPP_NO_EXCEPTIONS
+      report_impl(make_error_code(err), msg, ap);
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    } catch (...) {
+      va_end(ap);
+      throw;
+    }
+#endif  // _LIBCPP_NO_EXCEPTIONS
+    va_end(ap);
+    return error_value<T>();
   }
 
 private:
diff --git a/libcxx/src/filesystem/operations.cpp b/libcxx/src/filesystem/operations.cpp
--- a/libcxx/src/filesystem/operations.cpp
+++ b/libcxx/src/filesystem/operations.cpp
@@ -667,27 +667,20 @@
 
 filesystem_error::~filesystem_error() {}
 
-#if defined(_LIBCPP_WIN32API)
-#define PS_FMT "%ls"
-#else
-#define PS_FMT "%s"
-#endif
-
 void filesystem_error::__create_what(int __num_paths) {
   const char* derived_what = system_error::what();
   __storage_->__what_ = [&]() -> string {
-    const path::value_type* p1 = path1().native().empty() ? PS("\"\"") : path1().c_str();
-    const path::value_type* p2 = path2().native().empty() ? PS("\"\"") : path2().c_str();
     switch (__num_paths) {
-    default:
+    case 0:
       return detail::format_string("filesystem error: %s", derived_what);
     case 1:
-      return detail::format_string("filesystem error: %s [" PS_FMT "]", derived_what,
-                                   p1);
+      return detail::format_string("filesystem error: %s [" PATH_CSTR_FMT "]",
+                                   derived_what, path1().c_str());
     case 2:
-      return detail::format_string("filesystem error: %s [" PS_FMT "] [" PS_FMT "]",
-                                   derived_what, p1, p2);
+      return detail::format_string("filesystem error: %s [" PATH_CSTR_FMT "] [" PATH_CSTR_FMT "]",
+                                   derived_what, path1().c_str(), path2().c_str());
     }
+    _LIBCPP_UNREACHABLE();
   }();
 }
 
@@ -1455,11 +1448,11 @@
   error_code m_ec;
   file_status st = detail::posix_stat(p, &m_ec);
   if (!status_known(st))
-    return err.report(m_ec, "cannot access path \"" PS_FMT "\"", p);
+    return err.report(m_ec, "cannot access path " PATH_CSTR_FMT, p.c_str());
 
   if (!exists(st) || !is_directory(st))
-    return err.report(errc::not_a_directory, "path \"" PS_FMT "\" is not a directory",
-                      p);
+    return err.report(errc::not_a_directory,
+                      "path " PATH_CSTR_FMT " is not a directory", p.c_str());
 
   return p;
 }
diff --git a/libcxx/test/support/filesystem_test_helper.h b/libcxx/test/support/filesystem_test_helper.h
--- a/libcxx/test/support/filesystem_test_helper.h
+++ b/libcxx/test/support/filesystem_test_helper.h
@@ -634,9 +634,7 @@
       additional_msg = opt_message + ": ";
     }
     auto transform_path = [](const fs::path& p) {
-      if (p.native().empty())
-        return std::string("\"\"");
-      return p.string();
+      return "\"" + p.string() + "\"";
     };
     std::string format = [&]() -> std::string {
       switch (num_paths) {