cc/toolchains/make_variable.bzl

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# Licensed under the Apache License, Version 2.0 (the "License");
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"""Rules to turn make variable substitution into targets."""

load(":cc_toolchain_info.bzl", "MakeVariableInfo")

visibility("public")

def _cc_make_variable_impl(ctx):
    return [
        MakeVariableInfo(
            label = ctx.label,
            key = ctx.attr.variable_name,
            value = ctx.attr.value,
        ),
    ]

cc_make_variable = rule(
    implementation = _cc_make_variable_impl,
    attrs = {
        "value": attr.string(mandatory = True),
        "variable_name": attr.string(mandatory = True),
    },
    doc = """
This is used to declare that key / value substitutions for use in make-variable
substitutions in `copts` and other attributes.

See also: https://bazel.build/reference/be/make-variables

Example:

```
load("//cc/toolchains:make_variable.bzl", "cc_make_variable")

cc_make_variable(
    name = "macos_stack_substitution",
    value = "-Wframe-larger-than=100000000 -Wno-vla",
    variable_name = "STACK_FRAME_UNLIMITED",
)
```
""",
    provides = [
        MakeVariableInfo,
    ],
)