Qt 6 and CUDA fail to compile

cwade

I am trying to use CUDA in conjunction with Qt 6 and am unable to get it to compile. I am using a completely empty project, except for a main.cpp and a cuda class (.h/.cu). When I try to import any Qt class into the .cu class, the program fails to compile. Here is the project setup:

CMakeLists.txt:

cmake_minimum_required(VERSION 3.14)

project(Qt6CUDA LANGUAGES CXX CUDA)

set(CMAKE_INCLUDE_CURRENT_DIR ON)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Core)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Core)

add_executable(Qt6CUDA
  main.cpp
  cuda_class.h
  cuda_class.cu
)

set_property(TARGET ${PROJECT_NAME} PROPERTY CUDA_ARCHITECTURES 87)

# Qt 6 requires C++ 17
target_compile_options(${PROJECT_NAME} PRIVATE $<$<COMPILE_LANGUAGE:CUDA>:
    --std=c++17;
    -Zc:__cplusplus>)

target_link_libraries(Qt6CUDA Qt${QT_VERSION_MAJOR}::Core)

main.cpp:

#include <QCoreApplication>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    return a.exec();
}

cuda_class.h:

#ifndef CUDACLASS_H
#define CUDACLASS_H

class CudaClass
{
    public:
        CudaClass();
};

#endif // CUDACLASS_H

cuda_class.cu:

#include "cuda_class.h"

#include <QVector> // This line prevents the program from compiling

CudaClass::CudaClass()
{

}

Starting with the CMake, I simply enable language support for CUDA add compile options for C++ 17 (since Qt 6 requires C++ 17). I added a simple CUDA class that only includes QVector as an example. It does not seem to matter what Qt class I include, it fails in the same way for all I have tried.

When I try to compile I get the following output:

13:23:01: Running steps for project Qt6CUDA...
13:23:01: Starting: "C:\Program Files\CMake\bin\cmake.exe" --build C:/Users/i3w/Documents/build-Qt6CUDA-Desktop_Qt_6_3_0_MSVC2019_64bit-Debug --target all
[0/1 ?/sec] Re-running CMake...
-- Configuring done
-- Generating done
-- Build files have been written to: C:/Users/i3w/Documents/build-Qt6CUDA-Desktop_Qt_6_3_0_MSVC2019_64bit-Debug
[1/4 19.4/sec] Automatic MOC and UIC for target Qt6CUDA
[2/3 1.0/sec] Building CUDA object CMakeFiles\Qt6CUDA.dir\cuda_class.cu.obj
FAILED: CMakeFiles/Qt6CUDA.dir/cuda_class.cu.obj 
C:\PROGRA~1\NVIDIA~2\CUDA\v11.7\bin\nvcc.exe -forward-unknown-to-host-compiler -DQT_CORE_LIB -DUNICODE -DWIN32 -DWIN64 -D_ENABLE_EXTENDED_ALIGNED_STORAGE -D_UNICODE -D_WIN64 -IC:\Users\i3w\Documents\build-Qt6CUDA-Desktop_Qt_6_3_0_MSVC2019_64bit-Debug -IC:\Users\i3w\Documents\Qt6CUDA -IC:\Users\i3w\Documents\build-Qt6CUDA-Desktop_Qt_6_3_0_MSVC2019_64bit-Debug\Qt6CUDA_autogen\include -isystem=C:\Qt\6.3.0\msvc2019_64\include\QtCore -isystem=C:\Qt\6.3.0\msvc2019_64\include -isystem=C:\Qt\6.3.0\msvc2019_64\mkspecs\win32-msvc -D_WINDOWS -Xcompiler="/W3 /GR /EHsc" -Xcompiler="-MDd -Zi -Ob0 -Od /RTC1" --generate-code=arch=compute_87,code=[compute_87,sm_87] --std=c++17 -Zc:__cplusplus -std=c++17 -MD -MT CMakeFiles\Qt6CUDA.dir\cuda_class.cu.obj -MF CMakeFiles\Qt6CUDA.dir\cuda_class.cu.obj.d -x cu -c C:\Users\i3w\Documents\Qt6CUDA\cuda_class.cu -o CMakeFiles\Qt6CUDA.dir\cuda_class.cu.obj -Xcompiler=-FdCMakeFiles\Qt6CUDA.dir\,-FS
C:\Qt\6.3.0\msvc2019_64\include\QtCore/qlogging.h(156): warning #1394-D: field of class type without a DLL interface used in a class with a DLL interface

C:\Qt\6.3.0\msvc2019_64\include\QtCore/qtypeinfo.h(114): error: expected an expression
          detected during instantiation of class "QTypeInfoMerger<T, Ts...> [with T=std::pair<T1, T2>, Ts=<T1, T2>]" 
C:\Qt\6.3.0\msvc2019_64\include\QtCore/qpair.h(62): here

C:\Qt\6.3.0\msvc2019_64\include\QtCore/qtypeinfo.h(114): error: fold expression does not refer to a parameter pack
          detected during instantiation of class "QTypeInfoMerger<T, Ts...> [with T=std::pair<T1, T2>, Ts=<T1, T2>]" 
C:\Qt\6.3.0\msvc2019_64\include\QtCore/qpair.h(62): here

C:\Qt\6.3.0\msvc2019_64\include\QtCore/qtypeinfo.h(115): error: expected an expression
          detected during instantiation of class "QTypeInfoMerger<T, Ts...> [with T=std::pair<T1, T2>, Ts=<T1, T2>]" 
C:\Qt\6.3.0\msvc2019_64\include\QtCore/qpair.h(62): here

C:\Qt\6.3.0\msvc2019_64\include\QtCore/qtypeinfo.h(115): error: fold expression does not refer to a parameter pack
          detected during instantiation of class "QTypeInfoMerger<T, Ts...> [with T=std::pair<T1, T2>, Ts=<T1, T2>]" 
C:\Qt\6.3.0\msvc2019_64\include\QtCore/qpair.h(62): here

C:\Qt\6.3.0\msvc2019_64\include\QtCore/qbytearray.h(91): warning #1394-D: field of class type without a DLL interface used in a class with a DLL interface

C:\Qt\6.3.0\msvc2019_64\include\QtCore/qstring.h(1099): warning #1394-D: field of class type without a DLL interface used in a class with a DLL interface

C:\Qt\6.3.0\msvc2019_64\include\QtCore/qstringmatcher.h(85): warning #1394-D: field of class type without a DLL interface used in a class with a DLL interface

4 errors detected in the compilation of "C:/Users/i3w/Documents/Qt6CUDA/cuda_class.cu".
cuda_class.cu
ninja: build stopped: subcommand failed.
13:23:03: The process "C:\Program Files\CMake\bin\cmake.exe" exited with code 1.
Error while building/deploying project Qt6CUDA (kit: Desktop Qt 6.3.0 MSVC2019 64bit)
When executing step "Build"
13:23:03: Elapsed time: 00:02.

This same setup used to work with Qt 5 and older C++ language standards. The issue seems to be related to fold expressions used in qtypeinfo.h. If the #include <QVector> is not included in the .cu file, everything compiles file. Note, I am not trying to use any Qt in CUDA device code, simply import and use Qt classes within host only functions.

I am building with MSVC 2019 64-bit, Qt 6.3.0, and NVCC version 11.7 . This is the kit configuration:

sthlm58

@cwade Did you manage to solve this issue (in a way that doesn't require to remove Qt from *.cu files)?

Irodov

@sthlm58 I have the same problem, did any of you find a solution?

Xinlong

I am having exactly the same problem.