[llvm] [MC] Set SHF_EXCLUDE for AArch64 (and other) build attributes sections (PR #125824)

[Hans Wennborg via llvm-commits]

zmodem wrote:

Thanks for the quick reply!

I'm a bit concerned that we're making this dependent on the LLD version. For example, someone using Clang 20 with LLD 19 will get these extra sections (and as we've seen in our case, the size can be significant if there are many .o files.)

If the intention is that LLD (and other linkers) without explicit support for these attribute sections should drop them, isn't SHF_EXCLUDE the right answer? A linker which does support these sections can still process them any way they want, right?

> Setting SHF_EXCLUDE could have some unintended consequences with interoperation with GNU ld.

I suppose this would be an issue if they filter out SHF_EXCLUDE before checking for SHT_AARCH64_ATTRIBUTES. I don't have any aarch64 ld around to check with.

> I think the best way forward for now is to make a placeholder LLD patch that just discards the AArch64 Build Attributes section.

That will solve our problem :) I'm not sure it's best solution, but I'm not an expert in this area.

https://github.com/llvm/llvm-project/pull/125824