Bug: -Werror=nonnull when compiling with GCC on MINGW32

[dlech]

Version

No response

Summary

In the WinRT Python bindings project, I tried building on MINGW32 using GCC 13 with -Werror -Wall -Wextra compiler options. This triggers -Werror=nonnull in winrt/base.h (see full error below).

Is this a GCC bug or something that can/should be fixed in cppwrint?

Reproducible example

See https://github.com/pywinrt/pywinrt/actions/runs/5987024544/job/16240788415

Can be reproduced by checking out commit referenced by that run and running the commands in the `test.yaml` file.

Expected behavior

GCC should compile without errors like MSVC and Clang.

Actual behavior

FAILED: CMakeFiles/_winrt_testcomponent.dir/winrt-TestComponent/py.TestComponent.cpp.obj
C:\msys64\mingw32\bin\c++.exe -D_WIN32_WINNT=_WIN32_WINNT_WIN10 -D_winrt_testcomponent_EXPORTS -IC:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt -IC:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/pywinrt -IC:/Users/david/Documents/GitHub/pywinrt/projection/winrt-TestComponent/cppwinrt -IC:/Users/david/Documents/GitHub/pywinrt/projection/winrt-TestComponent -isystem C:/msys64/mingw32/include/python3.11 -std=gnu++20 -Werror -Wall -Wextra -Wa,-mbig-obj -MD -MT CMakeFiles/_winrt_testcomponent.dir/winrt-TestComponent/py.TestComponent.cpp.obj -MF CMakeFiles\_winrt_testcomponent.dir\winrt-TestComponent\py.TestComponent.cpp.obj.d -o CMakeFiles/_winrt_testcomponent.dir/winrt-TestComponent/py.TestComponent.cpp.obj -c C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-TestComponent/py.TestComponent.cpp
In file included from C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/Windows.Foundation.h:6,
                 from C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/pywinrt/pybase.h:9,
                 from C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-TestComponent/py.TestComponent.cpp:3:
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::abi_GetRuntimeClassName(void**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; I = {winrt::Windows::Foundation::Collections::IIterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >}; int32_t = int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7202:50:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetRuntimeClassName(void**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; I = winrt::Windows::Foundation::Collections::IIterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; Enable = void; int32_t = int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7200:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7583:35: error: 'this' pointer is null [-Werror=nonnull]
 7583 |                 return this->outer()->GetRuntimeClassName(name);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1767:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetRuntimeClassName(void**)'
 1767 |             virtual int32_t __stdcall GetRuntimeClassName(void** name) noexcept = 0;
      |                                       ^~~~~~~~~~~~~~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::abi_GetTrustLevel(winrt::Windows::Foundation::TrustLevel*) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; I = {winrt::Windows::Foundation::Collections::IIterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >}; int32_t = int]':        
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7207:44:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetTrustLevel(winrt::Windows::Foundation::TrustLevel*) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; I = winrt::Windows::Foundation::Collections::IIterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; Enable = void; int32_t = int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7205:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7593:35: error: 'this' pointer is null [-Werror=nonnull]
 7593 |                 return this->outer()->GetTrustLevel(trustLevel);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1768:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetTrustLevel(winrt::Windows::Foundation::TrustLevel*)'
 1768 |             virtual int32_t __stdcall GetTrustLevel(Windows::Foundation::TrustLevel* level) noexcept = 0;
      |                                       ^~~~~~~~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::abi_GetRuntimeClassName(void**) [with D = py::python_iterable<winrt::hstring>; I = {winrt::Windows::Foundation::Collections::IIterable<winrt::hstring>}; int32_t = int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7202:50:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetRuntimeClassName(void**) [with D = py::python_iterable<winrt::hstring>; I = winrt::Windows::Foundation::Collections::IIterable<winrt::hstring>; Enable = void; int32_t = int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7200:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7583:35: error: 'this' pointer is null [-Werror=nonnull]
 7583 |                 return this->outer()->GetRuntimeClassName(name);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1767:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetRuntimeClassName(void**)'
 1767 |             virtual int32_t __stdcall GetRuntimeClassName(void** name) noexcept = 0;
      |                                       ^~~~~~~~~~~~~~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::abi_GetTrustLevel(winrt::Windows::Foundation::TrustLevel*) [with D = py::python_iterable<winrt::hstring>; I = {winrt::Windows::Foundation::Collections::IIterable<winrt::hstring>}; int32_t = int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7207:44:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetTrustLevel(winrt::Windows::Foundation::TrustLevel*) [with D = py::python_iterable<winrt::hstring>; I = winrt::Windows::Foundation::Collections::IIterable<winrt::hstring>; Enable = void; int32_t = int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7205:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7593:35: error: 'this' pointer is null [-Werror=nonnull]
 7593 |                 return this->outer()->GetTrustLevel(trustLevel);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1768:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetTrustLevel(winrt::Windows::Foundation::TrustLevel*)'
 1768 |             virtual int32_t __stdcall GetTrustLevel(Windows::Foundation::TrustLevel* level) noexcept = 0;
      |                                       ^~~~~~~~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::GetIids(uint32_t*, winrt::guid**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; I = {winrt::Windows::Foundation::Collections::IIterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >}; int32_t = int; uint32_t = unsigned int]':        
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:8163:49:   required from 'winrt::impl::hresult_type winrt::implements<D, I>::GetIids(winrt::impl::count_type*, winrt::impl::guid_type**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; I = {winrt::Windows::Foundation::Collections::IIterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >}; winrt::impl::hresult_type = int; winrt::impl::count_type = unsigned int; winrt::impl::guid_type = winrt::guid]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7197:34:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetIids(uint32_t*, winrt::guid**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; I = winrt::Windows::Foundation::Collections::IIterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; Enable = void; int32_t = int; uint32_t = unsigned int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7195:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7573:35: error: 'this' pointer is null [-Werror=nonnull]
 7573 |                 return this->outer()->GetIids(count, array);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1766:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetIids(uint32_t*, winrt::guid**)'
 1766 |             virtual int32_t __stdcall GetIids(uint32_t* count, guid** ids) noexcept = 0;
      |                                       ^~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::GetIids(uint32_t*, winrt::guid**) [with D = py::python_iterable<winrt::hstring>; I = {winrt::Windows::Foundation::Collections::IIterable<winrt::hstring>}; int32_t = int; uint32_t = unsigned int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:8163:49:   required from 'winrt::impl::hresult_type winrt::implements<D, I>::GetIids(winrt::impl::count_type*, winrt::impl::guid_type**) [with D = py::python_iterable<winrt::hstring>; I = {winrt::Windows::Foundation::Collections::IIterable<winrt::hstring>}; winrt::impl::hresult_type = int; winrt::impl::count_type = unsigned int; winrt::impl::guid_type = winrt::guid]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7197:34:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetIids(uint32_t*, winrt::guid**) [with D = py::python_iterable<winrt::hstring>; I = winrt::Windows::Foundation::Collections::IIterable<winrt::hstring>; Enable = void; int32_t = int; uint32_t = unsigned int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7195:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7573:35: error: 'this' pointer is null [-Werror=nonnull]
 7573 |                 return this->outer()->GetIids(count, array);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1766:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetIids(uint32_t*, winrt::guid**)'
 1766 |             virtual int32_t __stdcall GetIids(uint32_t* count, guid** ids) noexcept = 0;
      |                                       ^~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::abi_GetRuntimeClassName(void**) [with D = py::python_iterable<winrt::hstring>::iterator; I = {winrt::Windows::Foundation::Collections::IIterator<winrt::hstring>}; int32_t = int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7202:50:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetRuntimeClassName(void**) [with D = py::python_iterable<winrt::hstring>::iterator; I = winrt::Windows::Foundation::Collections::IIterator<winrt::hstring>; Enable = void; int32_t = int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7200:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7583:35: error: 'this' pointer is null [-Werror=nonnull]
 7583 |                 return this->outer()->GetRuntimeClassName(name);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1767:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetRuntimeClassName(void**)'
 1767 |             virtual int32_t __stdcall GetRuntimeClassName(void** name) noexcept = 0;
      |                                       ^~~~~~~~~~~~~~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::abi_GetTrustLevel(winrt::Windows::Foundation::TrustLevel*) [with D = py::python_iterable<winrt::hstring>::iterator; I = {winrt::Windows::Foundation::Collections::IIterator<winrt::hstring>}; int32_t = int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7207:44:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetTrustLevel(winrt::Windows::Foundation::TrustLevel*) [with D = py::python_iterable<winrt::hstring>::iterator; I = winrt::Windows::Foundation::Collections::IIterator<winrt::hstring>; Enable = void; int32_t = int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7205:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7593:35: error: 'this' pointer is null [-Werror=nonnull]
 7593 |                 return this->outer()->GetTrustLevel(trustLevel);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1768:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetTrustLevel(winrt::Windows::Foundation::TrustLevel*)'
 1768 |             virtual int32_t __stdcall GetTrustLevel(Windows::Foundation::TrustLevel* level) noexcept = 0;
      |                                       ^~~~~~~~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::abi_GetRuntimeClassName(void**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >::iterator; I = {winrt::Windows::Foundation::Collections::IIterator<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >}; int32_t = int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7202:50:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetRuntimeClassName(void**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >::iterator; I = winrt::Windows::Foundation::Collections::IIterator<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; Enable = void; int32_t = int]'        
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7200:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7583:35: error: 'this' pointer is null [-Werror=nonnull]
 7583 |                 return this->outer()->GetRuntimeClassName(name);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1767:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetRuntimeClassName(void**)'
 1767 |             virtual int32_t __stdcall GetRuntimeClassName(void** name) noexcept = 0;
      |                                       ^~~~~~~~~~~~~~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::abi_GetTrustLevel(winrt::Windows::Foundation::TrustLevel*) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >::iterator; I = {winrt::Windows::Foundation::Collections::IIterator<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >}; int32_t = int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7207:44:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetTrustLevel(winrt::Windows::Foundation::TrustLevel*) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >::iterator; I = winrt::Windows::Foundation::Collections::IIterator<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; Enable = void; int32_t = int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7205:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7593:35: error: 'this' pointer is null [-Werror=nonnull]
 7593 |                 return this->outer()->GetTrustLevel(trustLevel);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1768:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetTrustLevel(winrt::Windows::Foundation::TrustLevel*)'
 1768 |             virtual int32_t __stdcall GetTrustLevel(Windows::Foundation::TrustLevel* level) noexcept = 0;
      |                                       ^~~~~~~~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::GetIids(uint32_t*, winrt::guid**) [with D = py::python_iterable<winrt::hstring>::iterator; I = {winrt::Windows::Foundation::Collections::IIterator<winrt::hstring>}; int32_t = int; uint32_t = unsigned int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:8163:49:   required from 'winrt::impl::hresult_type winrt::implements<D, I>::GetIids(winrt::impl::count_type*, winrt::impl::guid_type**) [with D = py::python_iterable<winrt::hstring>::iterator; I = {winrt::Windows::Foundation::Collections::IIterator<winrt::hstring>}; winrt::impl::hresult_type = int; winrt::impl::count_type = unsigned int; winrt::impl::guid_type = winrt::guid]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7197:34:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetIids(uint32_t*, winrt::guid**) [with D = py::python_iterable<winrt::hstring>::iterator; I = winrt::Windows::Foundation::Collections::IIterator<winrt::hstring>; Enable = void; int32_t = int; uint32_t = unsigned int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7195:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7573:35: error: 'this' pointer is null [-Werror=nonnull]
 7573 |                 return this->outer()->GetIids(count, array);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1766:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetIids(uint32_t*, winrt::guid**)'
 1766 |             virtual int32_t __stdcall GetIids(uint32_t* count, guid** ids) noexcept = 0;
      |                                       ^~~~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::GetIids(uint32_t*, winrt::guid**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >::iterator; I = {winrt::Windows::Foundation::Collections::IIterator<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >}; int32_t = int; uint32_t = unsigned int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:8163:49:   required from 'winrt::impl::hresult_type winrt::implements<D, I>::GetIids(winrt::impl::count_type*, winrt::impl::guid_type**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >::iterator; I = {winrt::Windows::Foundation::Collections::IIterator<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >}; winrt::impl::hresult_type = int; winrt::impl::count_type = unsigned int; winrt::impl::guid_type = winrt::guid]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7197:34:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetIids(uint32_t*, winrt::guid**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >::iterator; I = winrt::Windows::Foundation::Collections::IIterator<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; Enable = void; int32_t = int; uint32_t = unsigned int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7195:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7573:35: error: 'this' pointer is null [-Werror=nonnull]
 7573 |                 return this->outer()->GetIids(count, array);
      |                        ~~~~~~~~~~~^~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1766:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetIids(uint32_t*, winrt::guid**)'
 1766 |             virtual int32_t __stdcall GetIids(uint32_t* count, guid** ids) noexcept = 0;
      |                                       ^~~~~~~
cc1plus.exe: all warnings being treated as errors

Additional comments

No response

[alvinhochun]

I think I remember seeing this warning and I'm pretty sure it's a false positive. If you check the code you see it does this:

            if (this->outer())
            {
                return this->outer()->GetIids(count, array);
            }

So it does check the pointer to be non-null before calling the member function. I am not sure if this is a GCC bug though, maybe the concern is that multiple calls to this->outer() might return different values and it wants you to assign it to a local before checking?

Though you can find a list of bogus -Wnonnull warnings in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=wnonnull so this warning is known to be a bit buggy.

[kennykerr]

This was also flagged by internal static analysis tooling. It is sound but may worth fixing just to avoid the noise.

Related to #1341.

[sylveon]

The easiest fix would be

            if (const auto outer = this->outer())
            {
                return outer->GetIids(count, array);
            }

[kennykerr]

If that results in a clean build, feel free to offer a PR fix. There are a few such instances in base_implements.h.

[dlech]

The easiest fix would be

I tried this, but still triggers the the same error:

C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h: In instantiation of 'int32_t winrt::impl::root_implements<D, I>::GetIids(uint32_t*, winrt::guid**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >::iterator; I = {winrt::Windows::Foundation::Collections::IIterator<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >}; int32_t = int; uint32_t = unsigned int]':
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:8163:49:   required from 'winrt::impl::hresult_type winrt::implements<D, I>::GetIids(winrt::impl::count_type*, winrt::impl::guid_type**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >::iterator; I = {winrt::Windows::Foundation::Collections::IIterator<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >}; winrt::impl::hresult_type = int; winrt::impl::count_type = unsigned int; winrt::impl::guid_type = winrt::guid]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7197:34:   required from 'int32_t winrt::impl::produce_base<D, I, Enable>::GetIids(uint32_t*, winrt::guid**) [with D = py::python_iterable<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >::iterator; I = winrt::Windows::Foundation::Collections::IIterator<winrt::Windows::Foundation::Collections::IKeyValuePair<winrt::hstring, winrt::hstring> >; Enable = void; int32_t = int; uint32_t = unsigned int]'
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7195:27:   required from here
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7573:24: error: 'this' pointer is null [-Werror=nonnull]
 7573 |                 return outer->GetIids(count, array);
      |                        ^~~~~
C:/Users/david/Documents/GitHub/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:1766:39: note: in a call to non-static member function 'virtual int32_t winrt::impl::abi<winrt::Windows::Foundation::IInspectable>::type::GetIids(uint32_t*, winrt::guid**)'
 1766 |             virtual int32_t __stdcall GetIids(uint32_t* count, guid** ids) noexcept = 0;
      |                                       ^~~~~~~

[dlech]

I found that outer() was defined with constexpr in one template which seemed to be triggering the warning. I've made a pull request to remove it to avoid the warning.