================
@@ -14,16 +14,30 @@
#include <__type_traits/decay.h>
#include <__type_traits/is_same.h>
#include <__type_traits/remove_cvref.h>
+#include <__type_traits/type_identity.h>
#include <__type_traits/void_t.h>
#include <__utility/declval.h>
+#include <__utility/empty.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
-#if _LIBCPP_STD_VER >= 20
+#if __has_builtin(__builtin_common_type)
+
+template <class... _Args>
+struct common_type;
+
+template <class... _Args>
+using __common_type_t = typename common_type<_Args...>::type;
+
+template <class... _Args>
+struct common_type : __builtin_common_type<__common_type_t, __type_identity,
__empty, _Args...> {};
----------------
ldionne wrote:
@philnik777 This causes a problem when modules are enabled, because we'd have
to export `__builtin_common_type` from this module but I don't think there's
any way of doing that. That leads to errors of this kind:
```
# | In module 'std' imported from
/llvm/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.destr/dtor.pass.cpp:19:
# |
/llvm/build-runtimes/libcxx/test-suite-install/include/c++/v1/__chrono/duration.h:90:101:
error: no type named 'type' in 'std::common_type<long double, long double,
long>'
# | 90 | typedef typename common_type<typename _ToDuration::rep,
typename _FromDuration::rep, intmax_t>::type _Ct;
# | |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
# |
/llvm/build-runtimes/libcxx/test-suite-install/include/c++/v1/__chrono/duration.h:107:10:
note: in instantiation of member function
'std::chrono::__duration_cast<std::chrono::duration<long double>,
std::chrono::duration<long double, std::ratio<1, 1000>>>::operator()' requested
here
# | 107 | return __duration_cast<duration<_Rep, _Period>,
_ToDuration>()(__fd);
# | | ^
# |
/llvm/build-runtimes/libcxx/test-suite-install/include/c++/v1/__chrono/duration.h:220:24:
note: in instantiation of function template specialization
'std::chrono::duration_cast<std::chrono::duration<long double, std::ratio<1,
1000>>, long double, std::ratio<1>, 0>' requested here
# | 220 | : __rep_(chrono::duration_cast<duration>(__d).count()) {}
# | | ^
# |
/llvm/build-runtimes/libcxx/test-suite-install/include/c++/v1/__chrono/duration.h:385:33:
note: in instantiation of function template specialization
'std::chrono::duration<long double, std::ratio<1, 1000>>::duration<long double,
std::ratio<1>, 0>' requested here
# | 385 | return _Ct(__lhs).count() <=> _Ct(__rhs).count();
# | | ^
# |
/llvm/build-runtimes/libcxx/test-suite-install/include/c++/v1/__thread/this_thread.h:45:13:
note: in instantiation of function template specialization
'std::chrono::operator<=><long long, std::ratio<1, 1000>, long double,
std::ratio<1>>' requested here
# | 45 | if (__d < __max) {
# | | ^
# |
/llvm/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.destr/dtor.pass.cpp:63:29:
note: in instantiation of function template specialization
'std::this_thread::sleep_for<long long, std::ratio<1, 1000>>' requested here
# | 63 |
std::this_thread::sleep_for(std::chrono::milliseconds(250));
# | | ^
# | 1 error generated.
```
This didn't show up in the CI here because the modules CI doesn't run against
Clang trunk.
https://github.com/llvm/llvm-project/pull/99473
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