Find some way to expose closure lifetime in Rust return type.

[Xaeroxe]

Closures are allowed to reference data that may be dropped before the closure itself is dropped currently. This will result in undefined behavior.

This can't be meaningfully prevented in C++, but we aren't even preventing this in Rust.

[ErichDonGubler]

Is there a way that a 'static bound can be enforced on Closures, perhaps?

[Xaeroxe]

@ErichDonGubler That helps, but it's not a perfect fix. 'static is likely to be too restrictive, some uses of this could legitimately be for smaller lifetimes, and that wouldn't invoke undefined behavior. I have ideas for how to fix this but they aren't simple. It would involve moving as many definitions as possible out of C and into Rust. This would reverse the relationship for the code gen, to where we're using cbindgen rather than bindgen and likely driving the C compilation with Rust.

Since that new codegen approach would break current usage this refactor idea should probably be implemented as a new crate, and maybe even as an enhancement to cxx.