Use embedded LLD for linking

[sylvanc]

https://lld.llvm.org

This would eliminate the compiler's dependence on a C compiler for linking on Linux and on link.exe for linking on Windows.

LLD could be used as a library rather than needing to shell out to it.

[malthe]

LLD is still buggy on Mac: https://bugs.llvm.org/show_bug.cgi?id=32376

[sblessing]

Hey guys,

slowly but surely returning to this project: I have implemented this and just need to test it on Windows. This issue can be assigned to me and I make sure to submit a pull request soon.

Looks good on OSX, Linux and BSD!

[jemc]

Hey @sblessing! Welcome back.

I've sent you an invite to the org so you can be assigned this ticket. Once you accept, write back here and I'll assign you.

[Cogitri]

Hello,

due to ld.gold being rather buggy on musl (it just plain crashes if built without -fPIE: ld.gold: fatal error: build/release/stable: No error information) Alpine would be very interested in this too (or maybe I can somehow work around this for now by doing position executable binaries with ponyc? I don't know ponyc too well, sorry for my little knowledge :)

[SeanTAllen]

Yes, PIE is support already @Cogitri. If you pass default_pic=true to make when building Pony, it will use when linking all binaries. See https://www.ponylang.io/faq/#pic-compile-error

[Cogitri]

Hm, I already build ponyc with that option and just tried with ponyc --pic and it resulted in the same build error for pony-stable. Adding CFLAGS=-fPIE did the trick for ponyc, but I guess this leaves us with a non-functional compiler nontheless :/

[SeanTAllen]

We build and release for alpine all the time, so I'm not sure what issue you are running into. I suggest checking https://github.com/ponylang/ponyc/blob/master/.dockerhub/alpine/Dockerfile. Beyond that, please open a new issue as this is off topic for this issue.

[Cogitri]

Ah, sorry, I felt this was related to this due to using LLD as linker would fix this. I'll open a new issue.

[SeanTAllen]

No need to apologize @Cogitri. We have veered off from LLD though.

[sblessing]

I do have a running implementation with LLD. Unfortunately LLD is not yet where we need it to be and, and using LLD wouldn't remove vcvars.* :(

But I do think that LLD 9.0.0 looks promising.

[SeanTAllen]

@sblessing any update on LLD 9.0.0?

[sblessing]

@SeanTAllen Yes. I do have various examples running and so far it looks good. Do we need an RFC to eventually get this merged (and potentially at first have this as an experimental ponyc option)

[mfelsche]

I think an RFC would make sense to clarify how/if to expose it to users of ponyc (as an experimental flag or just replace using the system linker).
I know I tend to avoid the RFC-route, but in this case I would be fine to bring it in without RFC if it is only enabled via experimental option flag.

[SeanTAllen]

I'm looking to get this moving. See more in Zulip:

https://ponylang.zulipchat.com/#narrow/stream/189952-compiler-discussion/topic/Embedding.20lld.20in.20ponyc