Hi Ludo,

on second thought:

On Mon, 28 Jan 2019 15:39:33 +0100
Ludovic Courtès <ludo@gnu.org> wrote:
> > /gnu/store/fw4yy7cgb5ahs9s2ir00bawnsl5zj7db-mrustc-0.8.0/bin/mrustc[...]
> munmap_chunk(): invalid pointer

Maybe the above causes

> src/tools/cargo/src/crates-io/lib.rs:65: BUG:src/expand/proc_macro.cpp:941: Unexpected EOF while reading from child process

this.

Might be a memory double-free.  Exactly the kind of thing that Rust is supposed
to prevent is in the Rust compiler in C++ - well, at least the motivation for
having Rust is clear now ;-)

Can you try just

$ /gnu/store/fw4yy7cgb5ahs9s2ir00bawnsl5zj7db-mrustc-0.8.0/bin/mrustc src/tools/cargo/src/crates-io/lib.rs --crate-name crates_io --crate-type rlib --crate-tag 0_9_0 -g --cfg debug_assertions -O -o output/cargo-build/libcrates_io-0_9_0.hir -L output/cargo-build --extern curl=output/cargo-build/libcurl-0_4_6.hir --extern error_chain=output/cargo-build/liberror_chain-0_10_0.hir --extern serde=output/cargo-build/libserde-1_0_6.hir --extern serde_derive=output/cargo-build/libserde_derive-1_0_6.hir --extern serde_json=output/cargo-build/libserde_json-1_0_2.hir --extern url=output/cargo-build/liburl-1_4_0.hir -L output -L /gnu/store/fw4yy7cgb5ahs9s2ir00bawnsl5zj7db-mrustc-0.8.0/lib/mrust

in the build-failed kept source? (possibly with "ulimit -c unlimited" so it dumps core. mrustc is a normal C++ program, so normal debugging ways apply)

Or do I have access to the machine so I can do it?