Bazel: Document CROSSTOOL

[hanwen]

The entire crosstool format is probably too hairy, but we should definitely have examples how to configure embedded toolchains.

[ulfjack]

Assigning to myself as I designed the original crosstool format. But any help is appreciated.

[hanwen]

there are some examples on

https://github.com/google/bazel-examples

[hanwen]

the best documentation currently is the included CROSSTOOL

https://github.com/bazelbuild/bazel/blob/master/tools/cpp/CROSSTOOL

together with the proto definition,

https://github.com/bazelbuild/bazel/blob/master/src/main/protobuf/crosstool_config.proto

[davidzchen]

Perhaps let's add a brief definition of what the CROSSTOOL file is and what it is used for in the documentation on bazel.io? There are mentions of CROSSTOOL on the site but I don't think we ever explain what it is anywhere.

[damienmg]

internal ref: b/19928718

[kchodorow]

Note that there are now two wiki pages:

What the CROSSTOOL is and How to use a custom toolchain.

[hhclam]

Thanks! This is very helpful.

[damienmg]

FWIW I discovered we have an extensive documentation internally, we should maybe make it publicly available.

[hlopko]

So I checked the internal documentation and it's roughly on par with the public facing one. We will most definitely update the documentation after making CROSSTOOL more expressive and simpler in 2017, but that kind of goes without saying. So let me close this issue for now.