wanted: nelhage/rules_boost

[chenyuanrun]

Can somebody add boost support for bcr? Or may you accept a PR to add boost?

[fmeum]

Contributions in this area would be very welcome. https://github.com/nelhage/rules_boost appears to be a promising candidate for BCR inclusion.

[yl7890]

+1, but Boost is a very large repository and will likely need many maintainers. Some immediate questions:

• Is it better to include boost directly? Or is it better to include nelhage/rules_boost?
• If the former, is it better to have one monolithic boost repo? (e.g. boost/) or is it better to have many subrepos? (e.g. boost-accumulator, boost-any, etc...). Note that vcpkg seems to have both.
• If the latter, it is likely that lots of time will need to be spent writing adapters, since nelhage/rules_boost introduces many customizations.

[zaucy]

In the past I did fork the individual boost repositories and add BUILD and WORKSPACE files to them. https://github.com/bazelboost. No MODULE files since I did this before bcr was available. What I did was have the individual repositories and a single repository that creates an alias similar to the boostorg repository. Example alias @boost//libs/mp11:mp11 -> @com_github_bazelboost_mp11//:mp11 (source: https://github.com/bazelboost/boost/blob/main/libs/mp11/BUILD.bazel)

However, they are woefully unmaintained. I do use them, but I would consider it more of an experiment.

[aaronmondal]

Looks to me like the rules_boost BUILD.bazel is actively maintained, but I'm not sure whether this covers all libraries: https://github.com/nelhage/rules_boost/blob/master/BUILD.boost. I do agree though that the custom boost_library rules seem rather unnecessary to me. I think it would be a bit nicer to have "raw" rules_cc.

If it helps, I also played around with overlaying boost a while ago. Boost has a CMake build file generator tool. That tool can be rather easily adjusted to output Bazel BUILD files instead. The nice thing is that this way the dependencies for libraries are autogenerated. I believe I had to manually fix some smaller issues with these autogenerated files, but most targets "just worked" out of the box.

A relatively low maintenance overhead way to handle boost in the BCR may be to http_archive-fetch the packaged stable releases from the boost homepage and apply an overlay to it that adds a BUILD.bazel file, similarly to the bazel overlay in the llvm-project. Or we could just add a build file as a BCR-side patch :smile:

[hofbi]

https://github.com/nelhage/rules_boost/pull/553 ported rules_boost to bzlmod. Linking https://github.com/nelhage/rules_boost/issues/573 for cross reference.