Compiling rustc with non-standard flags

pmatos · 2018-12-03T20:46:11.070Z

How can I compile rust with non-standard compile flags?

The build system by using x.py feels very opaque. Is there a document somewhere how everything is put together and how to change the compile flags (which is what I am after)?

Centril · 2018-12-03T21:05:21.862Z

Perhaps the rustc guide can be helpful? https://rust-lang.github.io/rustc-guide/about-this-guide.html

mark-i-m · 2018-12-03T21:24:57.672Z

Hmm… I don’t think we have anything about the internals of x.py… may be a good thing to add.

cuviper · 2018-12-03T21:55:20.714Z

I believe rustc’s build does respect the RUSTFLAGS environment variable.

pmatos · 2018-12-04T07:34:54.576Z

The closest thing I find in the guide is: https://rust-lang.github.io/rustc-guide/how-to-build-and-run.html and yet there’s no mention of different compiler flags.

pmatos · 2018-12-04T07:35:55.781Z

So, if you want to compile, say with -Oz, would you do RUSTFLAGS=-Oz python x.py build? I assume this is the counterpart to CFLAGS. Is there a counterpart to LDFLAGS?

mark-i-m · 2018-12-04T18:23:18.895Z

@pmatos I’m curious what your use case is. Why do you want to compile with non-standard flags?

cuviper · 2018-12-04T18:32:13.582Z

pmatos:

Is there a counterpart to LDFLAGS ?

CFLAGS, CXXFLAGS, and LDFLAGS might still get used by some C/C++ components, but for the linker as invoked by rustc, I think you can stuff it in RUSTFLAGS="-Clink-arg=-foo -Clink-arg=-bar ...". Also remember that cc is used as the linker for most targets, so if you want to add a direct ld option, it would be like -Clink-arg=-Wl,option.

system · 2019-03-25T08:31:15.419Z

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