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rules_cc/cc/toolchains/tool_capability.bzl
Googler f364500ba8 Create a concept of a tool capability.
This should make the concept of "sentinel features" work correctly with known_features and enabled_features, rather than enabling them directly in features.

PiperOrigin-RevId: 681688437
Change-Id: I29184a2079ccfd0eb3a275439508a66ca61109af
2024-10-02 19:56:22 -07:00

86 lines
2.6 KiB
Python

# Copyright 2024 The Bazel Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Implementation of the cc_tool_capability rule."""
load(
":cc_toolchain_info.bzl",
"ArgsListInfo",
"FeatureConstraintInfo",
"FeatureInfo",
"ToolCapabilityInfo",
)
def _cc_tool_capability_impl(ctx):
ft = FeatureInfo(
name = ctx.attr.feature_name or ctx.label.name,
label = ctx.label,
enabled = False,
args = ArgsListInfo(
label = ctx.label,
args = (),
files = depset(),
by_action = (),
allowlist_include_directories = depset(),
),
implies = depset(),
requires_any_of = (),
mutually_exclusive = (),
# Mark it as external so that it doesn't complain if we say
# "requires" on a constraint that was never referenced elsewhere
# in the toolchain.
external = True,
overridable = True,
overrides = None,
allowlist_include_directories = depset(),
)
return [
ToolCapabilityInfo(label = ctx.label, feature = ft),
# Only give it a feature constraint info and not a feature info.
# This way you can't imply it - you can only require it.
FeatureConstraintInfo(label = ctx.label, all_of = depset([ft])),
]
cc_tool_capability = rule(
implementation = _cc_tool_capability_impl,
provides = [ToolCapabilityInfo, FeatureConstraintInfo],
doc = """A capability is an optional feature that a tool supports.
For example, not all compilers support PIC, so to handle this, we write:
```
cc_tool(
name = "clang",
src = "@host_tools/bin/clang",
capabilities = [
"//cc/toolchains/capabilities:supports_pic",
],
)
cc_args(
name = "pic",
requires = [
"//cc/toolchains/capabilities:supports_pic"
],
args = ["-fPIC"],
)
```
This ensures that `-fPIC` is added to the command-line only when we are using a
tool that supports PIC.
""",
attrs = {
"feature_name": attr.string(doc = "The name of the feature to generate for this capability"),
},
)