[gcc r12-4418] libstdc++: Make filesystem::path(path&&) always noexcept

[gcc r12-4418] libstdc++: Make filesystem::path(path&&) always noexcept

[Jonathan Wakely]

https://gcc.gnu.org/g:373acac1c8f2d64409ccea6aea409a0e15e80a6a

commit r12-4418-g373acac1c8f2d64409ccea6aea409a0e15e80a6a
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Oct 14 13:58:02 2021 +0100

    libstdc++: Make filesystem::path(path&&) always noexcept
    
    Since r12-4065 std::basic_string is always nothrow-move-constructible,
    so filesystem::path is too.
    
    That also means that path::_S_convert(T) is noexcept when returning its
    argument, because T is either a basci_string or basic_string_view, and
    will be moved into the return value.
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/fs_path.h (path(path&&)): Make unconditionally
            noexcept.
            (path::_S_convert(T)): Add condtional noexcept.

Diff:
---
 libstdc++-v3/include/bits/fs_path.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/include/bits/fs_path.h b/libstdc++-v3/include/bits/fs_path.h
index a63e4b9ab07..d13fb12455c 100644
--- a/libstdc++-v3/include/bits/fs_path.h
+++ b/libstdc++-v3/include/bits/fs_path.h
@@ -316,10 +316,7 @@ namespace __detail
 
     path(const path& __p) = default;
 
-    path(path&& __p)
-#if _GLIBCXX_USE_CXX11_ABI || _GLIBCXX_FULLY_DYNAMIC_STRING == 0
-      noexcept
-#endif
+    path(path&& __p) noexcept
     : _M_pathname(std::move(__p._M_pathname)),
       _M_cmpts(std::move(__p._M_cmpts))
     { __p.clear(); }
@@ -624,6 +621,7 @@ namespace __detail
     template<typename _Tp>
       static auto
       _S_convert(_Tp __str)
+      noexcept(is_same_v<typename _Tp::value_type, value_type>)
       {
 	if constexpr (is_same_v<typename _Tp::value_type, value_type>)
 	  return __str; // No conversion needed.