Generate Rust function types from C API?

[michaeljones]

I am working on a project which has a plugin system with a C API and some plugins are in Rust and some in C++. The part of the codebase that loads the plugins is in C++ but we're looking to port it to Rust. As a result I'd like to take the definition of the Plugin C API and generate code that'll help me when using libloading to load the plugin shared libraries and retrieve symbols from them.

From what I can tell, this involves having fn types like:

pub type get_id = fn() -> *const ::std::os::raw::c_char;

Rather than function signatures like:

extern "C" {
    pub fn get_id() -> *const ::std::os::raw::c_char;
}

I think it would be useful if bindgen could do that and I don't think it is completely out of the project scope though I'd understand if it is.

I'm quite new to this area so I might be overlooking things. If Rust has a typeof style operator then I guess I could get the former from the latter but I don't think that is possible? Maybe it is though.

Just an idea as I can't see it in the current configuration. I'd be happy to learn that it is already there. Or maybe there are reasons why it isn't feasible.

[torokati44]

This would be really useful for casting the function addresses obtained from dynamic libraries loaded at runtime (using libloading for example).

[torokati44]

FWIW the built-in integration with libloading (--dynamic-loading, that I just discovered) covers this use case fairly well.

[pvdrz]

This sounds like a reasonable but somewhat niche feature. It would be good to have more context about what you're trying to do.