Build modified versoin of std

[Yamakaky]

I'm working on std (in ~/dev/rust/rust), with a test crate in /tmp/test. I tried exporting XARGO_RUST_SRC and running xargo build, but it only build the test crate and not the modified std. How can I do that?

[japaric]

XARGO_RUST_SRC is ignored when you are using the nightly channel.

Try the hack-for-cmr branch.

$ cargo install --git https://github.com/japaric/xargo --branch hack-for-cmr

[Yamakaky]

Same problem...

[japaric]

Oh, wait. Are you trying to compile std for the host? That doesn't work right now. Xargo only builds sysroots when cross compiling (that's in the README)

[Yamakaky]

Oh, ok. Too bad.

[Yamakaky]

I get a lot of errors like

error: duplicate lang item in crate `core`: `debug_trait`.
  |
  = note: first defined in crate `core`.

[japaric]

@Yamakaky Please post more details. Contents of the crate (src/main.rs), Xargo.toml, the output of xargo build -v and whatever else you think may help.

[Yamakaky]

Xargo.toml

[target.x86_64-unknown-linux-gnu.dependencies.std]
features = []

Cargo.toml

[package]
name = "truc"
version = "0.1.0"
authors = ["yamakaky"]

[dependencies]

Output: https://0bin.net/paste/l12lhng4f7lA6Mu0#iLV1eE4mS2PfIA5FFQg6AEEdtS+UOBYQkv6bAg143Nm
main:

fn main() {
    panic!();
}

The rust source is updated to upstream/master.

[japaric]

This error comes from compiling std as a dylib, which is known to cause problems; see rust-lang/rust#36501. The interesting part is that you are getting a very different error from the one I saw when I reported rust-lang/rust#36501.

The workaround is to modify std's Cargo.toml like this:

diff --git a/src/libstd/Cargo.toml b/src/libstd/Cargo.toml
index a3996ead36..07a6c9cd49 100644
--- a/src/libstd/Cargo.toml
+++ b/src/libstd/Cargo.toml
@@ -7,7 +7,6 @@ build = "build.rs"
 [lib]
 name = "std"
 path = "lib.rs"
-crate-type = ["dylib", "rlib"]

 [dependencies]
 alloc = { path = "../liballoc" }

This needs to be fixed in the rust-lang/rust repo so that this (cargo building std) works without having to modify std source. That's what rust-lang/rust#36501 is tracking.

[Yamakaky]

Ok, thanks