RUSTFLAGS + a sysroot with spaces in its path = 😭

[steveklabnik]

When using cargo-xbuild to do things like "build an OS", you need to set the sysroot via RUSTFLAGS.

Here's an example rustc invocation on my machine that builds:

rustc --crate-name ux "C:\Users\Steve Klabnik\.cargo\registry\src\github.com-1ecc6299db9ec823\ux-0.1.2\src\lib.rs" --color always --crate-type lib --emit=dep-info,link -C panic=abort -C debuginfo=2 -C metadata=b446262c41a4777f -C extra-filename=-b446262c41a4777f --out-dir "C:\Users\Steve Klabnik\src\intermezzos\kernel\target\intermezzos\debug\deps" --target "\\?\C:\Users\Steve Klabnik\src\intermezzos\kernel\intermezzos.json" -L "dependency=C:\Users\Steve Klabnik\src\intermezzos\kernel\target\intermezzos\debug\deps" -L "dependency=C:\Users\Steve Klabnik\src\intermezzos\kernel\target\debug\deps" --cap-lints allow --sysroot "C:\Users\Steve Klabnik\src\intermezzos\kernel\target\sysroot"

The last bit is the important part:

--sysroot "C:\Users\Steve Klabnik\src\intermezzos\kernel\target\sysroot"

It appears the space in my username causes this to be impossible to set via RUSTFLAGS. With an invocation like this:

~\src\intermezzos\kernel [master ↑1]> $env:RUSTFLAGS="--sysroot ""C:\Users\Steve Klabnik\src\intermezzos\kernel\target\sysroot"""
~\src\intermezzos\kernel [master ↑1]> $env:RUSTFLAGS
--sysroot "C:\Users\Steve Klabnik\src\intermezzos\kernel\target\sysroot"

You can see that it's all good. However, this fails when passed to rustc:

> cargo build
error: failed to run `rustc` to learn about target-specific information

Caused by:
  process didn't exit successfully: `rustc - --crate-name ___ --print=file-names --sysroot "\"C:\Users\Steve" "Klabnik\src\intermezzos\kernel\target\sysroot\"" --crate-type bin --crate-type rlib --crate-type dylib --crate-type cdylib --crate-type staticlib --crate-type proc-macro` (exit code: 1)
--- stderr
error: multiple input filenames provided

I am not sure what to do here.

[codyps]

As a workaround, you could add build.rustflags = [ "--sysroot", "C:\Users\Steve Klabnik\src\intermezzos\kernel\target\sysroot" ] to some .cargo (https://doc.rust-lang.org/cargo/reference/config.html).

This issue basically stems from just doing .split(" ") on RUSTFLAGS in env_args().

One plausible solution is to define some escaping mechanism for RUSTFLAGS (or to maintain backwards compat, another env variable).

[ehuss]

Although it won't work in this situation (because it uses the wrong API), I added an experimental feature that allows you to specify lists in environment variables using TOML syntax. I could extend it to cover this situation, I doubt RUSTFLAGS starting with [ is ever valid.

[luser]

There is a shlex crate that implements POSIX shell style splitting which would probably make this work: https://docs.rs/shlex/0.1.1/shlex/

[nathan-osman]

For those looking for a temporary workaround, Windows still supports short filenames, so you could do:

"C:\Users\SteveK~1\.cargo\registry\src\github.com-..."

Ugly? Yes. But it works. 😛

[zshift]

Is there any traction on this? This issue has been open for 3 years now, and it's not obvious how to resolve without doing some searching.

[kupiakos]

If the problem is xargo setting RUSTFLAGS unconditionally then that can be fixed with the recently added feature of CARGO_ENCODED_RUSTFLAGS. This is Cargo's "fix" to the solution for xargo.

#10232 (comment)

[RalfJung]

This is the first time I hear about CARGO_ENCODED_RUSTFLAGS. Not sure since when it exists, but if it can replace setting RUSTFLAGS xargo should definitely use that, yeah. :D

However, at https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts it sounds more like CARGO_ENCODED_RUSTFLAGS is something that cargo sets for build scripts, not something it reads itself.

[RalfJung]

Ah, here it is. Yeah that sounds like exactly what we need!

[RalfJung]

I can confirm that with japaric/xargo#336, using a directory with a space for XARGO_HOME (which becomes the sysroot) works fine.

This issue should probably be closed then?

[weihanglo]

It seems to be there since 1.55.
https://github.com/rust-lang/cargo/blob/master/CHANGELOG.md#cargo-155-2021-09-09

Thanks for the reminder! Closing.