Template fails to build with linker errors on newest nightly when using fat LTO

[yodaldevoid]

As the title says. Based on CI and my testing, nightlies past 2023-12-01 cause the issue.

Looking at the commits between nightly-2023-12-01 and nightly-2023-12-02, there are a few changes around compiler-builtins, which is to be expected.

Commits of note:

• rust-lang/rust@8d69a1e
• rust-lang/rust@b592f29
• rust-lang/rust@a6f7596
• rust-lang/rust@5200817

Ill admit that I don't know enough about LTO to debug this further.

This may instead be an issue with the gba crate, but I was able to build an empty gba project without throwing errors. That said, I'm not entirely sure that empty project even did any memory access so it may not have hit this.

Linker errors

warning: memset changed binding to STB_WEAK

error: symbol 'memset' is already defined

warning: __aeabi_memclr4 changed binding to STB_WEAK

error: symbol '__aeabi_memclr4' is already defined

warning: __aeabi_memclr8 changed binding to STB_WEAK

error: symbol '__aeabi_memclr8' is already defined

warning: memcpy changed binding to STB_WEAK

error: symbol 'memcpy' is already defined

warning: __aeabi_memcpy changed binding to STB_WEAK

error: symbol '__aeabi_memcpy' is already defined

warning: __aeabi_memcpy8 changed binding to STB_WEAK

error: symbol '__aeabi_memcpy8' is already defined

warning: __aeabi_memset changed binding to STB_WEAK

error: symbol '__aeabi_memset' is already defined

warning: __aeabi_memset8 changed binding to STB_WEAK

error: symbol '__aeabi_memset8' is already defined

warning: __aeabi_memclr changed binding to STB_WEAK

error: symbol '__aeabi_memclr' is already defined

warning: __aeabi_memcpy4 changed binding to STB_WEAK

warning: __aeabi_memset4 changed binding to STB_WEAK

[gwilymk]

Sadly we've had this happen before and it's annoying to reproduce because from what I can tell, you need to have some non-trivial example which causes enough LTO to happen to make it actually break...

rust-lang/rust#108853 (comment) is the commit that broke it last time which is doubly strange. I haven't created an issue in the rust repo yet, but will probably do so tonight unless you have already

[gwilymk]

Latest nightly has fixed this now 🎉