Tracking issue for RFC 2137: Support defining C-compatible variadic functions in Rust (c_variadic) #44930
Description
This is a tracking issue for the RFC "Support defining C-compatible variadic functions in Rust" (rust-lang/rfcs#2137).
Steps:
- Implement the RFC (PR Support defining C compatible variadic functions #57760)
- Adjust documentation (see instructions on forge)
- Stabilization PR (see instructions on forge)
Unresolved questions:
- "When implementing this feature, we will need to determine whether the compiler
can provide an appropriate lifetime that prevents aVaListfrom outliving its
corresponding variadic function." - Continuing bikeshed on the
...syntax. - Ensure that even when this gets stabilized for regular functions, it is still rejected on
const fn. - What even is the semantics of this? What exactly is allowed and disallowed? Would be good to have a Miri implementation.
- borrowck problems: Poor interaction between NLL-borrowck, async, and c_variadic's
...desugaring (VaListImpl<'_>) #125431 - What exactly are the ABI requirements around variadic calls? What are the ABI compatibility rules? Do we have to be concerned about LLVM target features affecting variadic ABI?
- Soundness bug: Varargs are completely unchecked if passed as generics #61275
VaList<'_>does not carry its ABI in its type #141618
tcyrus, alex, demurgos, grihabor, ctaggart and 51 moree-ivkov, Dushistov, kamulos, lvyitian, bjoernager and 2 moretyped-sigterm and ari-at-backboneDCNick3, joseluis and flaribbit