Codeplay has written up a detailed run through of how they how they ensure C++ fundamental types are translated correctly from SYCL code through to OpenCL, retaining their correct size and signedness.
If you’re an application developer, this will help you learn a little about how SYCL works under the hood. If you’re looking to implement SYCL, this will help you find a way to get the compiler to do your lifting for you.