Re: [Mingw-w64-public] [PATCH] headers: Add more Set member template in HString class

[LIU Hao]

在 2024-10-07 16:06, Biswapriyo Nath 写道:

 From 80b827bfdf231bd49f9fe1d392b06a506a98a568 Mon Sep 17 00:00:00 2001
From: Biswapriyo Nath<nathbap...@gmail.com>
Date: Mon, 7 Oct 2024 08:03:43 +0000
Subject: [PATCH] headers: Add more Set member template in HString class

This fixes the following compiler error with gecko.

mozilla-unified/widget/windows/ToastNotification.cpp:832:14: error: no matching 
member function for call to 'Set'
   832 |   hr = aumid.Set(mAumid.ref().get());
       |        ~~~~~~^~~
corewrappers.h:58:25: note: candidate function not viable: no known conversion 
from
'typename raw_type<char16_t, int>::type' (aka 'char16ptr_t') to 'const HSTRING' 
(aka 'HSTRING__ *const') for 1st argument
corewrappers.h:53:25: note: candidate function not viable: requires 2 
arguments, but 1 was provided

Signed-off-by: Biswapriyo Nath<nathbap...@gmail.com>
---
  .../include/wrl/wrappers/corewrappers.h       | 33 +++++++++++++++++++
  1 file changed, 33 insertions(+)

Thanks. Pushed with a little change:






Without use of <type_traits> this can be implemented as

```
namespace Microsoft {
namespace WRL {

namespace Details {
  struct Dummy;
  Dummy convert_to_const_wchar_p_and_return_dummy(const wchar_t*) noexcept;
  template<typename T> T&& declval() noexcept;
}

namespace Wrappers {
  class HString {
    ... ...

    template<typename T>
    HRESULT Set(
      const T& str,
      decltype(
          ::Microsoft::WRL::Details::convert_to_const_wchar_p_and_return_dummy(
                                 ::Microsoft::WRL::Details::declval<const T&>())
        ) /* no name */ = ::Microsoft::WRL::Details::Dummy())
      noexcept
    {
      ... ...
    }
    ... ...
  };
}
```





--
Best regards,
LIU Hao

`std::is_convertible<T, const wchar_t*>` is equivalent to `std::is_convertible<T&&, const wchar_t*>` so it's not strictly the same with the `static_cast` below; I have changed it to `std::is_convertible<const T&, const wchar_t*>`. And I don't know why Microsoft decided to reinvent `EnableIf` and use a compiler intrinsic like that. There may be reasons that they don't want to (or can't) use standard C++ headers. If that's the reason, please let me know.

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