diff --git a/cc/find_cc_toolchain.bzl b/cc/find_cc_toolchain.bzl new file mode 100644 index 0000000..47940a2 --- /dev/null +++ b/cc/find_cc_toolchain.bzl @@ -0,0 +1,69 @@ +# pylint: disable=g-bad-file-header +# Copyright 2016 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. + +""" +Returns the current `CcToolchainInfo`. + +* When https://github.com/bazelbuild/bazel/issues/7260 is **not** flipped, current + C++ toolchain is selected using the legacy mechanism (`--crosstool_top`, + `--cpu`, `--compiler`). For that to work the rule needs to declare an + `_cc_toolchain` attribute, e.g. + +foo = rule( + implementation = _foo_impl, + attrs = { + "_cc_toolchain": attr.label(default = Label("@bazel_tools//tools/cpp:current_cc_toolchain")), + }, +) +* When https://github.com/bazelbuild/bazel/issues/7260 **is** flipped, current + C++ toolchain is selected using the toolchain resolution mechanism + (`--platforms`). For that to work the rule needs to declare a dependency on + C++ toolchain type: + + foo = rule( + implementation = _foo_impl, + toolchains = ["@rules_cc//cc:toolchain_type"], + ) + +We advise to depend on both `_cc_toolchain` attr and +`@rules_cc//cc:toolchain_type` for the duration of the migration. After +https://github.com/bazelbuild/bazel/issues/7260 is flipped (and support for old +Bazel version is not needed), it's enough to only keep the +`@rules_cc//cc:toolchain_type`. +""" + +def find_cc_toolchain(ctx): + """ +Returns the current `CcToolchainInfo`. + + Args: + ctx: The rule context for which to find a toolchain. + + Returns: + A CcToolchainInfo. + """ + + # Check the incompatible flag for toolchain resolution. + if hasattr(cc_common, "is_cc_toolchain_resolution_enabled_do_not_use") and cc_common.is_cc_toolchain_resolution_enabled_do_not_use(ctx = ctx): + if "//cc:toolchain_type" in ctx.toolchains: + return ctx.toolchains["//cc:toolchain_type"] + fail("In order to use find_cc_toolchain, you must include the '@rules_cc//cc:toolchain_type' in the toolchains argument to your rule.") + + # Fall back to the legacy implicit attribute lookup. + if hasattr(ctx.attr, "_cc_toolchain"): + return ctx.attr._cc_toolchain[cc_common.CcToolchainInfo] + + # We didn't find anything. + fail("In order to use find_ccc_toolchain, you must define the '_cc_toolchain' attribute on your rule or aspect.")