beta/stable regression with -g and -C debuginfo

[donhcd]

with this .cargo/config:

[build]
rustflags = ["-g", "-C", "target-feature=+avx2,+fma"]

on beta and nightly, cargo build gives me:

 % cargo build
   Compiling winapi-build v0.1.1
   Compiling backtrace v0.2.3
   Compiling gcc v0.3.43
   Compiling semver v0.1.20
error: -g and -C debuginfo both provided
error: -g and -C debuginfo both provided


error: -g and -C debuginfo both provided
error: -g and -C debuginfo both provided


error: Could not compile `winapi-build`.
Build failed, waiting for other jobs to finish...
error: Could not compile `backtrace`.
Build failed, waiting for other jobs to finish...
error: Could not compile `gcc`.
Build failed, waiting for other jobs to finish...
error: build failed

On stable, compilation works fine:

   Compiling scoped-tls v0.1.0
   Compiling regex-syntax v0.3.9
   Compiling fnv v1.0.5
   Compiling lazy_static v0.1.16
   Compiling num-traits v0.1.36
   Compiling winapi-build v0.1.1
...etc

On nightly and beta, I can add

[profile.dev]
debug = false

to my Cargo.toml to eliminate the compile errors, but I don't need to do this on stable.

Meta

sh-3.2$ rustup run nightly rustc --version --verbose
rustc 1.17.0-nightly (413a975e3 2017-02-23)
binary: rustc
commit-hash: 413a975e31584d1e22d158a70c6d3073b991a618
commit-date: 2017-02-23
host: x86_64-apple-darwin
release: 1.17.0-nightly
LLVM version: 3.9
sh-3.2$ rustup run beta rustc --version --verbose
^Prustc 1.16.0-beta.2 (bc15d5281 2017-02-16)
binary: rustc
commit-hash: bc15d5281c07828e7e5ca31af2051347f62629f5
commit-date: 2017-02-16
host: x86_64-apple-darwin
release: 1.16.0-beta.2
LLVM version: 3.9
sh-3.2$ rustup run stable rustc --version --verbose
rustc 1.15.1 (021bd294c 2017-02-08)
binary: rustc
commit-hash: 021bd294c039bd54aa5c4aa85bcdffb0d24bc892
commit-date: 2017-02-08
host: x86_64-apple-darwin
release: 1.15.1
LLVM version: 3.9

[nagisa]

This is not a rust-lang/rust regression. rustc did not accept -g and -C debuginfo at the same time since the first stable version I think.

[sfackler]

Due to rust-lang/cargo#3534, Cargo now uses -C debuginfo rather than -g when enabling debuginfo.

[alexcrichton]

@donhcd does passing -C debuginfo=2 work for you locally?

[alexcrichton]

(e.g. changing -g to -C debuginfo=2

[donhcd]

@alexcrichton yes, it looks like compilation works fine if I make that switch in .cargo/config

[alexcrichton]

Ok, excellent! We are likely to end up closing this (e.g. not reverting the initial change to Cargo), but we can be sure to document that -C debuginfo=... should be used or otherwise just allow composing these two flags.

[donhcd]

okay, sounds good to me. thanks for looking into this!

[brson]

Closing per discussion.