diff options
| author | Jonathan Wakely <jwakely@redhat.com> | 2021-05-06 19:14:42 +0100 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2021-05-07 23:45:52 +0100 |
| commit | a87ceadf17b4a899f3e74e2da8b6b209461d2742 (patch) | |
| tree | f8f0207607a553c7387377730fff224eeda5561c /libstdc++-v3/include/std/istream | |
| parent | 7c4c9fcc0de865876fb25fe75f4ed6e143bd48c0 (diff) | |
libstdc++: Fix constraints for rvalue stream insertion/extraction
The __rval_streamable() function was an attempt to test for
convertibility cheaply and without confusing diagnostics. It doesn't
work with Clang though, and is probably ill-formed.
Replace that helper function with a check for derivation from ios_base,
and use that in the alias templates __rvalue_stream_insertion_t and
__rvalue_stream_extraction_t. Use concepts for the constraints when
available.
libstdc++-v3/ChangeLog:
* include/std/istream (__rvalue_stream_extraction_t): Replace
use of __rval_streamable.
* include/std/ostream (__rvalue_stream_insertion_t): Likewise.
(__rval_streamable): Remove.
(_Require_derived_from_ios_base, __derived_from_ios_base): New
helper for checking constraints.
* testsuite/27_io/basic_istream/extractors_other/char/4.cc: Fix
reference to the wrong subclause of the standard.
* testsuite/27_io/basic_istream/extractors_other/wchar_t/4.cc:
Likewise.
* testsuite/27_io/basic_ostream/inserters_other/char/6.cc:
Likewise.
* testsuite/27_io/basic_ostream/inserters_other/wchar_t/6.cc:
Likewise.
* testsuite/27_io/basic_ostream/inserters_other/char/99692.cc:
New test.
* testsuite/27_io/filesystem/path/io/dr2989.cc: Adjust pruned
errors.
Diffstat (limited to 'libstdc++-v3/include/std/istream')
| -rw-r--r-- | libstdc++-v3/include/std/istream | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/libstdc++-v3/include/std/istream b/libstdc++-v3/include/std/istream index ea34cce6298..5ad60dbd709 100644 --- a/libstdc++-v3/include/std/istream +++ b/libstdc++-v3/include/std/istream @@ -958,12 +958,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // 2328. Rvalue stream extraction should use perfect forwarding // 1203. More useful rvalue stream insertion - // SFINAE helper to check constraints for operator>>(Istream&&, T&&). - // If the constraints are satisfied, it is an alias for Istream&&. +#if __cpp_lib_concepts + template<typename _Is, typename _Tp> + requires __derived_from_ios_base<_Is> + && requires (_Is& __is, _Tp&& __t) { __is >> std::forward<_Tp>(__t); } + using __rvalue_stream_extraction_t = _Is&&; +#else template<typename _Is, typename _Tp, - typename = decltype(std::__rval_streamable<_Is>() - >> std::declval<_Tp>())> + typename = _Require_derived_from_ios_base<_Is>, + typename = decltype(std::declval<_Is&>() >> std::declval<_Tp>())> using __rvalue_stream_extraction_t = _Is&&; +#endif /** * @brief Generic extractor for rvalue stream |