[libc++] Fix compilation error on platforms that don't implement std::tm

[ldionne]

Summary

Instead of mentioning tm directly in the definition of __convert_to_tm,
take it as a template argument. As a fly-by also fix incorrect Lit feature
(should have been no-localization instead of libcpp-has-no-localization).

[jloser]

libcxx/include/__chrono/convert_to_tm.h

14–15

Since we're taking the tm type as a template argument, we never explicitly mention std::tm now. Therefore, we should be able to remove this include, right?

[ldionne]

libcxx/include/__chrono/convert_to_tm.h

14–15

Yes, that sounds right.

[ldionne]

Address review comments.

[jloser]

LGTM!

[Mordante]

Which platforms don't have tm that we support? Can we add a CI for them?

libcxx/include/__chrono/convert_to_tm.h

31

Why is this change? As mentioned during our review it looks a bit odd now. However this function will get support for all chrono types that are formattable. An example of the "final" version can be seen in the function __make_tm
in https://reviews.llvm.org/D126592#change-qGrpldbZrZTa .

libcxx/test/std/time/time.syn/formatter.day.pass.cpp

9

Thanks! Nice catch.

[ldionne]

In D133490#3777447, @Mordante wrote:

Which platforms don't have tm that we support? Can we add a CI for them?

Apple's DriverKit is an example of that. Adding CI for that is on my todo list, but there's some stuff that needs to happen before that can be done.

libcxx/include/__chrono/convert_to_tm.h

31

Oh, yes, you're right. I'll undo that part.

[ldionne]

Apply review comments.

[Mordante]

In D133490#3778087, @ldionne wrote:

In D133490#3777447, @Mordante wrote:

Which platforms don't have tm that we support? Can we add a CI for them?

Apple's DriverKit is an example of that. Adding CI for that is on my todo list, but there's some stuff that needs to happen before that can be done.

Thanks for the info.

LGTM!

libcxx/include/__chrono/convert_to_tm.h

26

I'm not thrilled by this name, but when I have a better name I'll incorporate that in a next patch.

libcxx/include/__chrono/convert_to_tm.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP___CHRONO_CONVERT_TO_TM_H
 #define _LIBCPP___CHRONO_CONVERT_TO_TM_H
 
 #include <__chrono/day.h>
-#include <__concepts/same_as.h>
 #include <__config>
-#include <ctime>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17
 
-template <class _Tp>
-_LIBCPP_HIDE_FROM_ABI tm __convert_to_tm(const _Tp& __value) {
-  tm __result = {};
+// Convert chrono::days to the given tm type, which must have the same properties as std::tm.
+template <class _Tm>
+_LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const chrono::day& __value) {
+  _Tm __result = {};
 #  ifdef __GLIBC__
   __result.tm_zone = "UTC";
 #  endif
-
-  if constexpr (same_as<_Tp, chrono::day>)
-    __result.tm_mday = static_cast<unsigned>(__value);
-  else
-    static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
-
   return __result;
 }
 
 #endif //if _LIBCPP_STD_VER > 17
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___CHRONO_CONVERT_TO_TM_H

libcxx/include/__chrono/formatter.h

 ///      requirement of Table 97: Meaning of conversion specifiers
 ///      [tab:time.format.spec].
 ///
 /// When no chrono-specs are provided it uses the stream formatter.
 
 template <class _CharT, class _Tp>
 _LIBCPP_HIDE_FROM_ABI void __format_chrono_using_chrono_specs(
     const _Tp& __value, basic_stringstream<_CharT>& __sstr, basic_string_view<_CharT> __chrono_specs) {
-  tm __t              = std::__convert_to_tm(__value);
+  tm __t              = std::__convert_to_tm<tm>(__value);
   const auto& __facet = std::use_facet<time_put<_CharT>>(__sstr.getloc());
   for (auto __it = __chrono_specs.begin(); __it != __chrono_specs.end(); ++__it) {
     if (*__it == _CharT('%')) {
       auto __s = __it;
       ++__it;
       // We only handle the types that can't be directly handled by time_put.
       // (as an optimization n, t, and % are also handled directly.)
       switch (*__it) {

libcxx/test/std/time/time.cal/time.cal.day/time.cal.day.nonmembers/ostream.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// UNSUPPORTED: libcpp-has-no-localization
+// UNSUPPORTED: no-localization
 // UNSUPPORTED: libcpp-has-no-incomplete-format
 
 // TODO FMT Investigate Windows issues.
 // UNSUPPORTED msvc, target={{.+}}-windows-gnu
 
 // REQUIRES: locale.fr_FR.UTF-8
 // REQUIRES: locale.ja_JP.UTF-8
 

libcxx/test/std/time/time.syn/formatter.day.pass.cpp

 //===----------------------------------------------------------------------===//
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// UNSUPPORTED: libcpp-has-no-localization
+// UNSUPPORTED: no-localization
 // UNSUPPORTED: libcpp-has-no-incomplete-format
 
 // TODO FMT Investigate Windows issues.
 // UNSUPPORTED: msvc, target={{.+}}-windows-gnu
 
 // REQUIRES: locale.fr_FR.UTF-8
 // REQUIRES: locale.ja_JP.UTF-8