Transpile c to rust using c2rust?

[NobodyXu]

Recently bzip2 has used c2rust to transpile c to rust code, and gate it behind a feature flag.

I think doing the same on ring would be beneficial, it would:

• remove c compiler as a dependency, that would also enable easier cross compilation and LTO
• build script can be removed if transpiled rust code is used instead of the c code
• make it possible to run miri over ring

It would be a difficult though, especially because all the assembly has to be rewritten into rust as well.

Putting them into C as inline assembly might make it easier though.

[briansmith]

remove c compiler as a dependency, that would also enable easier cross compilation and LTO

We intend to replace the C code with Rust code, but mostly not with an automatic conversion. I think curve25519.c is the only C code that would potentially benefit from a conversion that starts with c2rust or similar automated conversion. The rest is better replaced by hand-written code. If you look at PR that rewrites aes_nohw.c in Rust, it is totally different than what c2rust would produce.

build script can be removed if transpiled rust code is used instead of the c code

The build script would still needed for the out-of-line assembly.

make it possible to run miri over ring

It would be a difficult though, especially because all the assembly has to be rewritten into rust as well.
Putting them into C as inline assembly might make it easier though.

I am more interested in an automated conversion of the PerlAsm code to Rust w/ inline assembly, because that's unrealistic to rewrite by hand.