[lld] [LLD][COFF] Detect weak reference cycles. (PR #104463)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> The weak aliases are an extension for MinGW right? In that case, what happens on ELF if you have weak alias cycles?

No, weak aliases (formally, "weak externals") are a common MS COFF feature. Unlike ELF (where you either have a weak defined or a weak undefined symbol), the COFF weak externals are a pointer to another symbol, to substitute, if the original one ended up undefined.

But in MinGW environments, the COFF weak externals can be used to try to emulate ELF style weak symbols.

https://github.com/llvm/llvm-project/pull/104463