Tracking Issue for `VaArgSafe` in bounds (`c_variadic_va_arg_safe`)

[maxdexh]

Feature gate: #![feature(c_variadic_va_arg_safe)]

This is a tracking issue for the VaArgSafe trait (part of rust-lang/rfcs#2137).
See also the tracking issue for c_variadic, where the API of this feature was intially stabilized on beta: #44930
Zulip stream: #t-libs > Implementing `VaArgSafe` on references is a breaking change

Public API

// core::ffi, reexported in std::ffi
pub impl(self) unsafe trait VaArgSafe {}

Steps / History

• Implementation: Support defining C compatible variadic functions #57760
• Destabilization PR: Destabilize VaArgSafe #162909
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• Should (thin) references implement the trait (and if so, what about extern types)? (see zulip and Add FCW for invalid C variadic arguments #162478)
• Function pointers are not VaArgSafe #153646

Footnotes

1. https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩

[maxdexh]

@rustbot label -S-tracking-unimplemented s-tracking-design-concerns