How do I split the source file into host and device to compile separately

[malixian]

I found the using the option -fsycl-device-only can only compile the SYCL device code. I want to find a way to only compile the SYCL host code.

[keryell]

Since SYCL is pure C++, if you compile the SYCL code with a normal host compiler, you should have the host code and it will work also on the host CPU.
Is this what you are locking for?
This is called host fallback mode in the SYCL jargon.

[AlexeySachkov]

@keryell is right, in order to compile only host part of the SYCL code, just compile it without any -fsycl flags, i.e. like it is a regular C++ app. You can find some examples in sycl/test/separate-compile