clang-check cannot deal with 32bits

[hummeleBop]

I have an issue with C++/WinRT v2.0.191111.2 on a minimalistic sample.
clang-check is useful to get more warnings in C++.

My C++ test file minimal.cpp:

#include <winrt/Windows.Foundation.Collections.h>
#include <winrt/Windows.Web.Syndication.h>
#include <iostream>

using namespace winrt;
using namespace Windows::Foundation;
using namespace Windows::Web::Syndication;

int main()
{
    winrt::init_apartment();

    Uri rssFeedUri{ L"https://blogs.windows.com/feed" };
    SyndicationClient syndicationClient;
    SyndicationFeed syndicationFeed = syndicationClient.RetrieveFeedAsync(rssFeedUri).get();
    for (const SyndicationItem syndicationItem : syndicationFeed.Items())
    {
        winrt::hstring titleAsHstring = syndicationItem.Title().Text();
        std::wcout << titleAsHstring.c_str() << std::endl;
    }
}

The commands used:

cppwinrt -i 10.0.18362.0 -verbose -out generated\
clang-check minimal.cpp -- --driver-mode=cl -m64 /std:c++17 /EHsc -Xclang -fcoroutines-ts -Xclang -isystem"C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Tools\MSVC\14.23.28105\include" -Xclang -isystem"C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\ucrt" -Xclang -isystem".\generated"

The previous commands work and behave correctly.
However when I try to replace -m64 with -m32 parameter, I get the following errors:

In file included from .\generated\winrt/Windows.Foundation.Collections.h:5:
.\generated\winrt/base.h(7607,14): error: no matching function for call to 'WINRT_TrySubmitThreadpoolCallback'
        if (!WINRT_TrySubmitThreadpoolCallback(callback, handle.address(), nullptr))
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\generated\winrt/base.h(412,24): note: candidate function not viable: no known conversion from '(lambda at .\generated\winrt/base.h:7602:25)' to
      'void (*)(void *, void *) __attribute__((stdcall))' for 1st argument
    int32_t  __stdcall WINRT_TrySubmitThreadpoolCallback(void(__stdcall *callback)(void*, void* context), void* context, void*) noexcept;
                       ^
.\generated\winrt/base.h(7638,56): error: no viable conversion from '(lambda at .\generated\winrt/base.h:7632:29)' to 'int32_t
      (*)(winrt::impl::com_callback_args *) __attribute__((stdcall))' (aka 'int (*)(winrt::impl::com_callback_args *) __attribute__((stdcall))')
            check_hresult(sta_context->ContextCallback(callback, &args, guid_of<ICallbackWithNoReentrancyToApplicationSTA>(), 5, nullptr));
                                                       ^~~~~~~~
.\generated\winrt/base.h(7632,29): note: candidate function
            auto callback = [](com_callback_args* args) noexcept -> int32_t
                            ^
.\generated\winrt/base.h(1809,70): note: passing argument to parameter 'callback' here
        virtual int32_t __stdcall ContextCallback(int32_t(__stdcall* callback)(com_callback_args*), com_callback_args* args, guid const& iid, int met...
                                                                     ^
2 errors generated.

[kennykerr]

Does clang-cl itself work for you in both architectures? I'm not a Clang expert, but if there's something obviously wrong feel free to suggest or contribute - we accept contributions. 😉

[hummeleBop]

clang-cl has the same issue.
Can't help on cppwinrt, it's really something I cannot handle.

[kennykerr]

clang-cl has the same issue.

Thanks, I'll take a look.

[hummeleBop]

clang-cl is probably not the ultimate goal for cppwinrt, and I utterly understand that.
However, being able to use clang-check with cppwinrt is really helpful.
clang-check can display a lot of useful warnings, I think it's relevant when a developer works on a UWP app.
Sadly, I'm not good enough to patch the repository for that.

[kennykerr]

We have teams using C++/WinRT with Clang. I'm just not personally all that familiar with it, but I will look into this. I do want to make sure it works with Clang. There are some issues with Clang not being able to handle some of the scale issues that C++/WinRT presents, but it should at least be able to compile basic projects.

[kennykerr]

I just tried this with the latest version of C++/WinRT:

clang-check minimal.cpp -- --driver-mode=cl -m64 /std:c++17 /EHsc -Xclang -fcoroutines-ts -I.

Seems to work without complaint.

Update: Oh, forgot to use -m32 - never mind.

So, this is related to the issue where VC will helpfully provide overloads for functions objects to match all calling conventions. Sadly, Clang does not do this.

Anyway, now that I know the problem I can easily work around it. Thanks for reporting this.