mirror of https://github.com/bazelbuild/rules_cc
126 lines
4.6 KiB
Python
126 lines
4.6 KiB
Python
# pylint: disable=g-bad-file-header
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# Copyright 2016 The Bazel Authors. All rights reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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Helpers for CC Toolchains.
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Rules that require a CC toolchain should call `use_cc_toolchain` and `find_cc_toolchain`
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to depend on and find a cc toolchain.
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* When https://github.com/bazelbuild/bazel/issues/7260 is **not** flipped, current
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C++ toolchain is selected using the legacy mechanism (`--crosstool_top`,
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`--cpu`, `--compiler`). For that to work the rule needs to declare an
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`_cc_toolchain` attribute, e.g.
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foo = rule(
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implementation = _foo_impl,
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attrs = {
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"_cc_toolchain": attr.label(
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default = Label(
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"@rules_cc//cc:current_cc_toolchain", # copybara-use-repo-external-label
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),
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),
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},
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)
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* When https://github.com/bazelbuild/bazel/issues/7260 **is** flipped, current
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C++ toolchain is selected using the toolchain resolution mechanism
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(`--platforms`). For that to work the rule needs to declare a dependency on
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C++ toolchain type:
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load(":find_cc_toolchain/bzl", "use_cc_toolchain")
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foo = rule(
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implementation = _foo_impl,
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toolchains = use_cc_toolchain(),
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)
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We advise to depend on both `_cc_toolchain` attr and on the toolchain type for
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the duration of the migration. After
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https://github.com/bazelbuild/bazel/issues/7260 is flipped (and support for old
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Bazel version is not needed), it's enough to only keep the toolchain type.
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"""
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CC_TOOLCHAIN_TYPE = "@bazel_tools//tools/cpp:toolchain_type" # copybara-use-repo-external-label
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def find_cc_toolchain(ctx, *, mandatory = True):
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"""
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Returns the current `CcToolchainInfo`.
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Args:
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ctx: The rule context for which to find a toolchain.
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mandatory: (bool) If this is set to False, this function will return None
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rather than fail if no toolchain is found.
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Returns:
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A CcToolchainInfo or None if the c++ toolchain is declared as
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optional, mandatory is False and no toolchain has been found.
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"""
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# Check the incompatible flag for toolchain resolution.
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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):
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if not CC_TOOLCHAIN_TYPE in ctx.toolchains:
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fail("In order to use find_cc_toolchain, your rule has to depend on C++ toolchain. See find_cc_toolchain.bzl docs for details.")
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toolchain_info = ctx.toolchains[CC_TOOLCHAIN_TYPE]
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if toolchain_info == None:
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if not mandatory:
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return None
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# No cpp toolchain was found, so report an error.
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fail("Unable to find a CC toolchain using toolchain resolution. Target: %s, Platform: %s, Exec platform: %s" %
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(ctx.label, ctx.fragments.platform.platform, ctx.fragments.platform.host_platform))
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if hasattr(toolchain_info, "cc_provider_in_toolchain") and hasattr(toolchain_info, "cc"):
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return toolchain_info.cc
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return toolchain_info
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# Fall back to the legacy implicit attribute lookup.
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if hasattr(ctx.attr, "_cc_toolchain"):
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return ctx.attr._cc_toolchain[cc_common.CcToolchainInfo]
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# We didn't find anything.
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if not mandatory:
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return None
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fail("In order to use find_cc_toolchain, your rule has to depend on C++ toolchain. See find_cc_toolchain.bzl docs for details.")
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def find_cpp_toolchain(ctx):
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"""Deprecated, use `find_cc_toolchain` instead.
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Args:
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ctx: See `find_cc_toolchain`.
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Returns:
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A CcToolchainInfo.
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"""
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return find_cc_toolchain(ctx)
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def use_cc_toolchain(mandatory = False):
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"""
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Helper to depend on the cc toolchain.
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Usage:
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```
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my_rule = rule(
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toolchains = [other toolchain types] + use_cc_toolchain(),
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)
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```
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Args:
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mandatory: Whether or not it should be an error if the toolchain cannot be resolved.
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Returns:
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A list that can be used as the value for `rule.toolchains`.
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"""
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return [config_common.toolchain_type(CC_TOOLCHAIN_TYPE, mandatory = mandatory)]
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