Tracking issue for `link_args` stabilization

[aturon]

This issue tracks stabilization for the #[link_args] attribute.

[aturon]

@alexcrichton (or anyone else), any ideas what the blockers are here?

[aturon]

From the reference:

The compiler's usage of the system linker is not guaranteed to continue in the future, and if the system linker is not used then specifying custom flags doesn't have much meaning.

[alexcrichton]

Some thoughts of mine:

• Right now we split arguments on spaces, so there's no way to specify an argument with a space in it
• This is super non-cross-platform. Even within one platform there's no guarantee that we'll always call the same linker.
• It's unclear what the "propagation semantics" of link args should be. For example if you build an rlib, should the arguments be passed to when that rlib is included in a linker invocation? Should it be passed upstream continuously after that is then later used in linker invocations?

[WiSaGaN]

Since we do not have a good solution for now, but as a system language, it is sometimes necessary to specify args like this (even only for specific platforms), put it behind a feature gate and only letting nightly branch to use it seems to be a compromise to make.

[iwinux]

Got hit by this issue when trying out https://gist.github.com/jansegre/043f5ab7f53e23890eed.

As LuaJIT requires, I need to link the binary with flags -pagezero_size 10000 -image_base 100000000, which seems only achievable via #[link_args = "..."].

Could this be done without using Rust nightly? Obviously link_args is not available as of Rust 1.6.0:

src/main.rs:1:1: 1:23 error: #[feature] may not be used on the stable release channel
src/main.rs:1 #![feature(link_args)]

[retep998]

You can use the command line flag -Clink-args="-pagezero_size 10000 -image_base 100000000" which does work fine (or cargo rustc -- -Clink-args="blah")

[comex]

It seems strange to allow -C link-args on the command line without -Z unstable-options, yet keep the source code equivalent unstable.

[retep998]

I'd rather we fix the issue with being unable to have spaces in the linker arguments before stabilizing either of them. Unfortunately -Clink-args being stable makes that difficult.