Enforce toolchain used for building kernel? about microkit

[podhrmic]

Is there a specific reason for using gcc instead of clang? We had good experience cross compiling with clang for RISCV, and presumably the ARM support is only better.

[Ivan-Velickovic]

A benefit I like of using Clang over GCC would be that we can avoid the mess that is GCC cross-compiler toolchains since clang is just a single binary for compiling all architectures (as far as I know). I think that it does not matter too much as the toolchain is only required for building the SDK, user code can use whatever toolchain it wants to.

[Ivan-Velickovic]

I have played around with Clang a bit and unfortunately it seems like it is not much better. In order to build everything needed for Microkit you would need the LLVM linker as well as other tools such as llvm-ar. These are not always easy to install depending on your host system.

I don't find this to be much better than GCC given you now have to acquire various binaries on your system to fully compile everything. With GCC there's just one path you need, but you need to have a separate one for each architecture.

Neither solution is ideal.

To my knowledge, the Zig C compiler is the only truly portable C compiler however the project is too immature and buggy to be used for production software such as Microkit (in my opinion).

[Ivan-Velickovic]

I'm going to close the issue as #50 has been merged.

Regarding whether to use Clang over GCC, I don't feel strongly towards either. All other seL4 Foundation projects use GCC which may cause Microkit to end up sticking with GCC. I will definitely keep this in mind as the decision is not finalised yet and will decide what to do as we converge Microkit dependencies with current seL4 dependencies. Thanks for bringing it up @podhrmic.