Invoking std::thread with class operator()() that has CWinThread as base fails

Question

Background:

My project is C++ MFC. But I am writing the code using modern C++ as the standard evolves. Currently, I invoke threads sometimes using std::thread (later code) and sometimes the MFC CreateThread complete with required waitForSingleObject and thread priority parameter. Clearly, the std::thread is more elegant and therefore more maintainable. It is important to over time make the code consistent and drop old idioms where possible.

Problem:

But invoking std::thread with a class Baz in sample code below that has CWinThread as its base, fails to find a std::thread constructor.

Sample Code:

struct Caz {};
struct Baz : public CWinThread // works if base is Caz
{
  void operator()() {}
};

std::shared_ptr< Baz > b;
b = std::make_shared< Baz >();

std::thread bazThread( *b ); // error: can't find a constructor when CWinThread is base, but can for Caz as base

When the base class is CWinThread it fails to resolve, but when the base class is Caz it works fine. Both Caz and CWinThread have default constructors.

Why is CWinThread making it fail?

Edit1:

The error message set is:

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\memory(2057,35): error C2665: 'std::tuple::tuple': none of the 2 overloads could convert all the argument types

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\tuple(321,5): message : could be 'std::tuple::tuple(std::tuple &&)'

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\tuple(320,5): message : or 'std::tuple::tuple(const std::tuple &)'

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\memory(2056,59): message : while trying to match the argument list '(_Ty2)'

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\memory(2056,59): message : with

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\memory(2056,59): message : [

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\memory(2056,59): message : _Ty2=Baz 1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\memory(2056,59): message : ]

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\thread(53): message : see reference to function template instantiation 'std::unique_ptr<_Tuple,std::default_delete<_Ty>> std::make_unique<_Tuple,_Ty2&,0>(_Ty2 &)' being compiled

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\thread(53): message : with

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\thread(53): message : [

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\thread(53): message : _Ty=_Tuple,

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\thread(53): message : _Ty2=Baz

1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\thread(53): message : ]

1>E:\Hiveware\trunk\Windows\hives\Hiveware\SdcdcHiveware\GrammarSdcdcHiveware.cpp(153): message : see reference to function template instantiation 'std::thread::thread<_Ty2&,,void>(_Fn)' being compiled

1>E:\Hiveware\trunk\Windows\hives\Hiveware\SdcdcHiveware\GrammarSdcdcHiveware.cpp(153): message : with

1>E:\Hiveware\trunk\Windows\hives\Hiveware\SdcdcHiveware\GrammarSdcdcHiveware.cpp(153): message : [

1>E:\Hiveware\trunk\Windows\hives\Hiveware\SdcdcHiveware\GrammarSdcdcHiveware.cpp(153): message : _Ty2=Baz,

1>E:\Hiveware\trunk\Windows\hives\Hiveware\SdcdcHiveware\GrammarSdcdcHiveware.cpp(153): message : _Fn=Baz &

1>E:\Hiveware\trunk\Windows\hives\Hiveware\SdcdcHiveware\GrammarSdcdcHiveware.cpp(153): message : ]

1>Done building project "SdcdcHiveware.vcxproj" -- FAILED.

Edit2:

// FUNCTION TEMPLATE make_unique
template <class _Ty, class... _Types, enable_if_t<!is_array_v<_Ty>, int> = 0>
_NODISCARD unique_ptr<_Ty> make_unique(_Types&&... _Args) { // make a unique_ptr
    return unique_ptr<_Ty>(new _Ty(_STD forward<_Types>(_Args)...));
}

Answer 1

Tentative answer unless someone finds a workaround.

std::thread cannot be used in MFC projects for class types that inherit from CWinThread, also called user threads for which sample code may be found at Creating Threads.

For traditional windows worker threads invoking std::thread instead works fine.