rustbuild misses -pthread on final link

[ishitatsuyuki]

Logs available at https://paste.rs/M2c

    ./configure \
        --prefix=/usr \
        --enable-ninja \
        --llvm-root=/usr \
        --disable-codegen-tests \
        --jemalloc-root=/usr/lib/libjemalloc_pic.a
# BROKEN: https://github.com/rust-lang/rust/issues/35349
#        --jemalloc-root=/usr/lib/

    export RUSTFLAGS="$RUSTFLAGS -C link-args=-lffi"
    export CFLAGS="$CFLAGS -fPIC -w"

[alexcrichton]

This is typically the reponsibility of the standard library but I don't see -lpthread in the output at all... odd! What system are you on? (to help in reproducing this)

[ishitatsuyuki]

Arch amd64, with the provided compilation flags.

[ishitatsuyuki]

@alexcrichton: "-l pthread" is passed but possibly somehow truncated in the log. Sorry for the inconvenience.

Back to the topic, you're passing -lpthread(wrong), not -pthread(correct).

[sfackler]

IIRC -pthread only differs from -lpthread by changing configuration for the macro processor which is not relevant when linking.

[ishitatsuyuki]

@sfackler: -pthread is not passed even when compiling, causing it referencing to undefined symbols.

[ishitatsuyuki]

There's two way to achieve this:

1. Allow arbitrary flags in cargo:rustc-flags to add -pthread.
2. Refactor and add it in the gcc crate.

[ishitatsuyuki]

https://github.com/rust-lang/rust/blob/master/mk/cfg/x86_64-unknown-linux-gnu.mk#L13

@alexcrichton This is not by luck, this is intended in the old buildsystem.

[tamird]

829b5de