make install on top of an already installed rust results in breakage

[jwise]

After doing a make install (of an early rust-0.3.tar.gz) on top of an already installed Rust (from git a few days ago), I now get the following error while compiling things:

joshua@icfp:~$ cat > hello.rs
fn main(args: ~[str]) {
    io::println("hello world from '" + args[0] + "'!");
}
joshua@icfp:~$ rustc hello.rs
hello.rs:1:0: 1:0 error: multiple matching crates for `core`
hello.rs:1 fn main(args: ~[str]) {
           ^
note: candidates:
note: path: /usr/local/lib/rustc/i686-unknown-linux-gnu/lib/libcore-d27e4777a53c3e50-0.2.so
note: meta: #[link(name = "core",
       vers = "0.2",
       uuid = "c70c24a7-5551-4f73-8e37-380b11d80be8",
       url = "https://github.com/mozilla/rust/tree/master/src/libcore")]
note: path: /usr/local/lib/rustc/i686-unknown-linux-gnu/lib/libcore-d27e4777a53c3e50-0.3.so
note: meta: #[link(name = "core",
       vers = "0.3",
       uuid = "c70c24a7-5551-4f73-8e37-380b11d80be8",
       url = "https://github.com/mozilla/rust/tree/master/src/libcore")]
error: aborting due to previous error

There should be logic to override with newer versions, or otherwise warn about this sort of thing.

[killerswan]

Shouldn't rustc be smart enough to find the right libcore-xxx-yyy.so?

[killerswan]

Hmm, so src/rustc/rustc.rc actually does ask for linking with use core(vers = "0.3"), so this is a matter of rustc not forcing its need on the program or library it is compiling...

[killerswan]

Well, even adding use core(vers = "0.3"); to a demo program's .rc file isn't enough to resolve this.

[tav]

I just ran into the same problem:

rusty.rc:1:0: 1:0 error: multiple matching crates for `core`
rusty.rc:1 // Public Domain (-) 2012 The Rusty Authors.
           ^
note: candidates:
note: path: /usr/local/lib/rustc/x86_64-apple-darwin/lib/libcore-c3ca5d77d81b46c1-0.4.dylib
note: meta: name = "core"
note: meta: vers = "0.4"
note: meta: uuid = "c70c24a7-5551-4f73-8e37-380b11d80be8"
note: meta: url = "https://github.com/mozilla/rust/tree/master/src/libcore"
note: path: /usr/local/lib/rustc/x86_64-apple-darwin/lib/libcore-c3ca5d77d81b46c1-0.5.dylib
note: meta: name = "core"
note: meta: vers = "0.5"
note: meta: uuid = "c70c24a7-5551-4f73-8e37-380b11d80be8"
note: meta: url = "https://github.com/mozilla/rust/tree/master/src/libcore"
error: aborting due to previous error

A work-around is to be explicit about the use of core, i.e. add the following to a crate file:

#[no_core];

extern mod core(vers = "0.5");
use core::*;

Just importing a specific version of core doesn't work, e.g.

extern mod core(vers = "0.5");

I am guessing this is because somewhere we implicitly add the following to a crate file:

extern mod core;
use core::*;

Given that multi-version installs of rust are only going to be increasing in number, it might help create better second impressions if we fixed this somehow.

Could we add the current version to the implicit extern mod core; ?

[catamorphism]

#3225 supersedes this.