Undefined external symbols from compiler_builtins

[fenhl]

I have a project where I'm experimenting with introducing Rust code into an existing codebase by compiling it into a static library for a custom target and linking it using armips. This process no longer works on the latest nightly because armips complains about undefined external symbols such as _rnvntcse1eqnti5u6g_17compiler_builtins4math5atan2.

A minimal example is at https://github.com/fenhl/rust-builtins-min which can be tested by running python build.py after installing armips (scoop install extras/armips on Windows, see https://github.com/Kingcom/armips for binaries and build instructions for other platforms).

I ran cargo-bisect-rustc on the original project where I ran into this (not the minimal example, hence the different script in the command line) and it points to #123719 as the commit that introduced the regression.

cargo-bisect-rustc output

searched nightlies: from nightly-2022-06-21 to nightly-2024-04-16
regressed nightly: nightly-2024-04-15
searched commit range: 0bf471f...0d8b334
regressed commit: 29b1207

bisected with cargo-bisect-rustc v0.6.8

Host triple: x86_64-pc-windows-msvc
Reproduce with:

cargo bisect-rustc --start=2022-06-21 -c rust-src --script python -- .\cargo-bisect-rustc-test.py

[Noratrieb]

rust-lang/compiler-builtins@0.1.108...0.1.109

I suspect it's rust-lang/compiler-builtins#577

[Noratrieb]

@Amjad50 @Amanieu

[Amjad50]

Thanks for letting me know.

The changes in 0.1.109 do not work as expected, I'm working on a fix here rust-lang/compiler-builtins#594, I'll test it with this project.

[Amjad50]

So after looking around and trying to fix the issue, the main issue is from armips, it doesn't handle weak symbols correctly

Added a quick small fix here, Kingcom/armips#242, but not sure if the maintainer is around anymore