User provided platform constraints

[nickjmeyer]

Hello,

Using this repo, I currently have a tool chain set up to build for target Linux x86_64 and Linux aarch64 all on a host Linux x86_64 machine. I have a third platform I need to support that is another Linux aarch64 target. Is there a way to provide additional platform constraints to enable defining multiple platforms with the same target arch / os? From reading through the repository, it appears not given the exec_compatible_with attribute is set to only specify os and arch.

If not supported, any code pointers as to how you'd extend it to do so?

[fmeum]

This could be wired up in a similar way to target_settings defined here:

toolchains_llvm/toolchain/internal/repo.bzl

Line 240 in e3c57fc

"target_settings": attr.string_list_dict(

The LLVM extension could receive new tag_classes for, say, extra_target_compatible_with and extra_exec_compatible_with that are similar to the ones defined here (just taking an attr.label_list instead of an attr.label:

toolchains_llvm/toolchain/extensions/llvm.bzl

Lines 82 to 89 in e3c57fc

	"toolchain_root": tag_class(
	attrs = {
	"name": attr.string(doc = "Same name as the toolchain tag.", default = "llvm_toolchain"),
	"targets": attr.string_list(doc = "Specific targets, if any; empty list means this applies to all."),
	"label": attr.label(doc = "Dummy label whose package path is the toolchain root package."),
	"path": attr.string(doc = "Absolute path to the toolchain root."),
	},
	),

[jkurland-roku]

I've opened an MR with an implementation of this here (#371).

[nickjmeyer]

Thanks for the pointers!