Use __CUDA_ARCH__ outside device function

Accelerated Computing CUDA CUDA NVCC Compiler
1

Is the following legal in Cuda ?

foo.cu

#ifdef __CUDA_ARCH__
#define X 1
#else
#define X 0
#endif

__device__ __host__ int foo()
{
    return X;
}

CUDA documentation says that the host should not use __CUDA_ARCH__. So can we pretend the value is undefined? Also, can we use __CUDA_ARCH__ outsde a __device__ function? Even here in practice, it’s used inside, but the macro is defined outside the __device__ function.