[gcc/devel/omp/gcc-9] PR libstdc++/91786 fix compilation error with Clang

[Tobias Burnus]

https://gcc.gnu.org/g:5765ed7aaa5486c6e8eefc569247f58eda355474

commit 5765ed7aaa5486c6e8eefc569247f58eda355474
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Dec 11 13:45:56 2019 +0000

    PR libstdc++/91786 fix compilation error with Clang
    
    Backport from mainline
    2019-11-25  Jonathan Wakely  <jwakely@redhat.com>
    
    	PR libstdc++/91786
    	* include/bits/fs_path.h (filesystem_error): Move definition before
    	the use in u8path.
    
    From-SVN: r279223

Diff:
---
 libstdc++-v3/ChangeLog              |  9 ++++++
 libstdc++-v3/include/bits/fs_path.h | 59 +++++++++++++++++++------------------
 2 files changed, 40 insertions(+), 28 deletions(-)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 40a7116..60f3e34 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,12 @@
+2019-12-11  Jonathan Wakely  <jwakely@redhat.com>
+
+	Backport from mainline
+	2019-11-25  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/91786
+	* include/bits/fs_path.h (filesystem_error): Move definition before
+	the use in u8path.
+
 2019-12-10  Thomas Rodgers  <trodgers@redhat.com>
 
 	Backport from mainline
diff --git a/libstdc++-v3/include/bits/fs_path.h b/libstdc++-v3/include/bits/fs_path.h
index e56a0a7..5dc624d 100644
--- a/libstdc++-v3/include/bits/fs_path.h
+++ b/libstdc++-v3/include/bits/fs_path.h
@@ -612,6 +612,36 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
   size_t hash_value(const path& __p) noexcept;
 
+  /// Exception type thrown by the Filesystem library
+  class filesystem_error : public std::system_error
+  {
+  public:
+    filesystem_error(const string& __what_arg, error_code __ec);
+
+    filesystem_error(const string& __what_arg, const path& __p1,
+		     error_code __ec);
+
+    filesystem_error(const string& __what_arg, const path& __p1,
+		     const path& __p2, error_code __ec);
+
+    filesystem_error(const filesystem_error&) = default;
+    filesystem_error& operator=(const filesystem_error&) = default;
+
+    // No move constructor or assignment operator.
+    // Copy rvalues instead, so that _M_impl is not left empty.
+
+    ~filesystem_error();
+
+    const path& path1() const noexcept;
+    const path& path2() const noexcept;
+    const char* what() const noexcept;
+
+  private:
+    struct _Impl;
+    std::__shared_ptr<const _Impl> _M_impl;
+  };
+
+  /// Create a path from a UTF-8-encoded sequence of char
   template<typename _InputIterator>
     inline auto
     u8path(_InputIterator __first, _InputIterator __last)
@@ -642,6 +672,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 #endif
     }
 
+  /// Create a path from a UTF-8-encoded sequence of char
   template<typename _Source>
     inline auto
     u8path(const _Source& __source)
@@ -663,34 +694,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 #endif
     }
 
-  class filesystem_error : public std::system_error
-  {
-  public:
-    filesystem_error(const string& __what_arg, error_code __ec);
-
-    filesystem_error(const string& __what_arg, const path& __p1,
-		     error_code __ec);
-
-    filesystem_error(const string& __what_arg, const path& __p1,
-		     const path& __p2, error_code __ec);
-
-    filesystem_error(const filesystem_error&) = default;
-    filesystem_error& operator=(const filesystem_error&) = default;
-
-    // No move constructor or assignment operator.
-    // Copy rvalues instead, so that _M_impl is not left empty.
-
-    ~filesystem_error();
-
-    const path& path1() const noexcept;
-    const path& path2() const noexcept;
-    const char* what() const noexcept;
-
-  private:
-    struct _Impl;
-    std::__shared_ptr<const _Impl> _M_impl;
-  };
-
   struct path::_Cmpt : path
   {
     _Cmpt(basic_string_view<value_type> __s, _Type __t, size_t __pos)