Stabilize PATH option for --print KIND=PATH by Urgau · Pull Request #114183 · rust-lang/rust (original) (raw)

This PR propose stabilizing the PATH option for --print KIND=PATH. This option was previously added in #113780 (as insta-stable before being un-stablized in #114139).

Description of the PATH option:

A filepath may optionally be specified for each requested information kind, in the format --print KIND=PATH, just like for --emit. When a path is specified, information will be written there instead of to stdout.

Description of the original PR [link]:

Support --print KIND=PATH command line syntax

As is already done for --emit KIND=PATH and -L KIND=PATH.

In the discussion of #110785, it was pointed out that --print KIND=PATH is nicer than trying to apply the single global -o path to --print's output, because in general there can be multiple print requests within a single rustc invocation, and anyway -o would already be used for a different meaning in the case of link-args and native-static-libs.

I am interested in using --print cfg=PATH in Buck2. Currently Buck2 works around the lack of support for --print KIND=PATH by indirecting through a Python wrapper script to redirect rustc's stdout into the location dictated by the build system.

From skimming Cargo's usages of --print, it definitely seems like it would benefit from --print KIND=PATH too. Currently it is working around the lack of this by inserting --crate-name=___ --print=crate-name so that it can look for a line containing ___ as a delimiter between the 2 other --print informations it actually cares about. This is commented as a "HACK" and "abuse". https://github.com/rust-lang/cargo/blob/31eda6f7c360d9911f853b3014e057db61238f3e/src/cargo/core/compiler/build_context/target_info.rs#L242

cc @dtolnay
r? @jackh726