On Thu, 2022-02-10 at 15:14 -0800, Alexei Starovoitov wrote: > So adding > _Static_assert(sizeof(type_in_skel) == const_size_from_kernel); > to skel.h would force users to pick types that are the same > both in bpf prog and in corresponding user space part. I'm not sure users have this much control over the definition of the types in their program though. If a kernel and uapi typedef differ in size, this approach would force the user to use kernel types for the entire program. If, for example, pid_t is a different size in glibc and the kernel, it would force you out of using any glibc functions taking pid_t (and potentially all of glibc depending on how entangled the headers are). By normalizing to stdint types, we're saying that the contract represented by the skel does not operate with either uapi or kernel types and it's up to you to ensure you use the right one (or mix and match, if you can). It feels fundamentally more permissive to different types of situations than forcing the skel user to only use kernel types or refactor their program to isolate the kernel type leakage to only the compilation unit using the skel.
