I have a C++ project that contains a buffer_logic.cu file and a main.cpp file. the .cu file contains the following code, which sets a buffer in memory to a given colour.

#include "cuda_runtime.h"
#include "device_launch_parameters.h"

__global__ void set_buffer_colour(unsigned int colour, const unsigned int width, const unsigned height, unsigned int* buffer) {
    // code to edit buffer goes here
    }
}

static void clear_screen_to_colour(const unsigned int colour, const unsigned int width, const unsigned int height, unsigned int* memory_buffer, unsigned int* gpu_buffer)
{
        dim3 threads_per_block(16, 16);
        dim3 num_blocks((width + threads_per_block.x - 1) / threads_per_block.x,
            (height + threads_per_block.y - 1) / threads_per_block.y);

        set_buffer_colour<<<num_blocks, threads_per_block>>>(colour, width, height, gpu_buffer);
        cudaMemcpy(memory_buffer, gpu_buffer, width * height * sizeof(unsigned int), cudaMemcpyDeviceToHost);
}

the main.cpp file is as follows:

 #include "buffer_logic.cu"

int main() {
    unsigned int* buffer;
    cudaMalloc(&buffer, 100 * 100 * sizeof(unsigned int));
    unsigned int* buffer_gpu;
    cudaMalloc(&buffer_gpu, 100 * 100 * sizeof(unsigned int));
    clear_screen_to_colour(0, 100, 100, buffer, buffer_gpu);
    return 0;
}

The .vcxproj file contains the lines:

<CudaCompile Include="buffer_logic.cu">
      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">false</ExcludedFromBuild>
      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Release|x64'">false</ExcludedFromBuild>
    </CudaCompile>

However, it appears to compile using the same compiler as main.cpp, as compilation throws the error syntax error: '<', because of the line set_buffer_colour<<<num_blocks, threads_per_block>>>(colour, width, height, gpu_buffer);

I tried to force it to compile using nvcc with command prompt, using the command nvcc -o my_project C:\Users\Daniel\source\repos\my_project\main.cpp however, this resulted in the same compiler error as before: syntax error: '<'

including the main function in the buffer_logic.cu fixed the issue, but this is not what I want.

I am new to CUDA programming. Why is this happening, and how do I fix it?