I currently use Rust to generate a static library for FFI consumption. In some public interfaces, I call other FFI public interfaces as primarily a wrapper with a few tweaks. I'd like to mark these "inner" functions as inline, however, this seems to cause them to not show up in the final staticlib.

Given this drastically simplified example:

/// lib.rs #![no_std] #[no_mangle] pub extern "C" fn square_plus_one(input: usize) -> usize { square(input) + 1 } #[no_mangle] #[inline] pub extern "C" fn square(input: usize) -> usize { input * input } use core::panic::PanicInfo; /// This function is called on panic. #[panic_handler] fn panic(_info: &PanicInfo) -> ! { loop { // Prevent loop mis-optimization continue; } }

# Cargo.toml [package] name = "inline-ffi" version = "0.2.0" edition = "2018" description = "" license = "" documentation = "" homepage = "" repository = "" [lib] crate-type = ["staticlib"] [profile.dev] panic = "abort" [profile.release] panic = "abort"

The square_plus_one function makes it to the static library, but the square function does not:

nm -nSC ./target/release/libinline_ffi.a | rg square 0000000000000000 0000000000000009 T square_plus_one 

If I remove the #[inline] attribute, we see both functions in the static lib:

nm -nSC ./target/release/libinline_ffi.a | rg square 0000000000000000 0000000000000008 T square 0000000000000000 0000000000000009 T square_plus_one 

The relevant docs don't seem to hint that #[inline] can prevent #[no_mangle]/pub extern "C" items from surviving all the way to the final library, or that they shouldn't be used together.

I would expect any function marked pub extern "C" and/or #[no_mangle] should be present in the final artifact, regardless of #[inline] attributes.

I see this behavior on 1.43.1 stable, as well as a recent nightly. I don't know if this is a regression, as this is the first time I've run into this.

Thanks!

Edit: Simplified Cargo.toml profile settings, they are not needed to reproduce.

This issue has been assigned to @doctorn via this comment.