[PATCH] D96914: [ELF] Add -z start-stop-gc to let __start_/__stop_ not retain C identifier name sections

Thu Nov 4 15:03:47 PDT 2021

jrtc27 added a comment.

In D96914#3109977 <https://reviews.llvm.org/D96914#3109977>, @MaskRay wrote:

> Mach-O ld64 uses the same model as current ld.lld -z start-stop-gc.

This isn't relevant. I am not objecting to the semantics, I am objecting to the *timeline* for the *change* in semantics. Mach-O has always (I assume) had those semantics, and had ways to deal with them. The ways to deal with them for ELF and the change in semantics happened back-to-back, rather than introducing the mechanism for explicitly retaining the sections but keeping the old default for several years so that when you come time to change the default there are no issues with assuming the mechanism to retain the sections exists. I feel like a broken record repeating this but you don't seem to acknowledge this as being my complaint so I have to keep telling you why your characterisation of my objection is inaccurate.

> The way ldc uses `__start___minfo` is also incompatible with GNU ld 2015-10.

Which was deemed a bug in GNU ld, and got fixed. There have been bugs in its --gc-sections implementation over the years that got fixed, that doesn't mean everything that didn't used to work is regarded as something you shouldn't do.

> There are several ways to make FreeBSD work.
>
> Finally, as I mentioned in the ldc issue, the llvm-project<13.0.0 and ld.lld>=13.0.0 is not supported way using LTO (probably weaker than "unsupported").

I don't know why you're talking about LTO all of a sudden, we've been talking about using ld.lld --gc-sections on plain already-compiled-to-machine-code .o files, no LTO in sight (well, GC'ing sections is _technically_ optimisation done at link time, but so are all manner of things linkers do, and they're not what people mean by LTO).

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https://reviews.llvm.org/D96914