Stop relying on rpath

[brson]

Followup to #5219 and #11746. Can we completely eliminate our usage of rpath? Doing so would make our linkage more consistent across platforms since it doesn't work on windows. Nominating.

[alexcrichton]

I think that the largest difficulty for this is that we build rustc dynamically, and this means that if you have a fresh install of rust in a new location it won't work by default (you'll have to munge your os library path).

If we could print out some helpful instructions of what to do, then I think that would be a much better situation, but I'm also not entirely sure how we'd do that.

[brson]

If we defaulted to static linking then there would it would be easier to justify making people use LD_LIBRARY_PATH when they opt in to dylibs.

[alexcrichton]

The only consideration that I have about static linking is that you'll install 5 copies of librustc (as opposed to 3):

with static linking

• rustdoc
• rustc
• rustpkg
• rustlib/rustc.dylib
• rustlib/rustc.so

without static linking

• librustc.so
• rustlib/rustc.dylib
• rustlib/rustc.so

That being said, our distributions are already pretty big, so maybe this isn't much of a concern?

I agree though that if we statically linked everything then we could easily take this route of action

[jhasse]

IMO this is a concern.

What's wrong with the current approach (link rust's own tools dynamically)? It works fine on windows since the DLLs are in the bin folder and for everything else it will soon link statically (#11253).

[alexcrichton]

Another use case for this came up on IRC.

If you've got a rust installed locally in /usr/local, then when you try to recompile rust again, the rpath for all the stage0-produced libraries will have something pointing into /usr/local. Apparently on some platforms when you run the stage1 rustc, this means that you'll pick up all the /usr/local libs at runtime instead of the stage0-produced libs (causing errors until you uninstall rustc).

[pnkfelix]

Accepted for 1.0, P-backcompat-lang.

[thestinger]

Rust now builds and passes tests with --disable-rpath. This feature could be disabled by default or completely removed, with LD_LIBRARY_PATH as a suggestion for those who want to use a dynamically linked rustc in their home directory on *nix.