src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainRule.java - bazel - Git at Google

 // Copyright 2014 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.
 package com.google.devtools.build.lib.rules.cpp;

 import static com.google.devtools.build.lib.packages.Attribute.attr;
 import static com.google.devtools.build.lib.packages.BuildType.LABEL;
 import static com.google.devtools.build.lib.packages.BuildType.LICENSE;
 import static com.google.devtools.build.lib.packages.Type.BOOLEAN;

 import com.google.devtools.build.lib.analysis.BaseRuleClasses;
 import com.google.devtools.build.lib.analysis.PlatformConfiguration;
 import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
 import com.google.devtools.build.lib.analysis.TemplateVariableInfo;
 import com.google.devtools.build.lib.analysis.config.transitions.NoTransition;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.packages.Type;

 /**
  * Rule definition for compiler definition.
  */
 public final class CcToolchainRule implements RuleDefinition {

   public static final String TOOLCHAIN_CONFIG_ATTR = "toolchain_config";

   /** Default attribute name where rules store the reference to cc_toolchain */
   public static final String CC_TOOLCHAIN_DEFAULT_ATTRIBUTE_NAME = ":cc_toolchain";

   public static final String CC_TOOLCHAIN_DEFAULT_ATTRIBUTE_NAME_FOR_STARLARK = "$cc_toolchain";

   /** Default attribute name for the c++ toolchain type */
   public static final String CC_TOOLCHAIN_TYPE_ATTRIBUTE_NAME = "$cc_toolchain_type";

   public static final String ALLOWED_LAYERING_CHECK_FEATURES_ALLOWLIST =
       "disabling_parse_headers_and_layering_check_allowed";
   public static final String ALLOWED_LAYERING_CHECK_FEATURES_TARGET =
       "//tools/build_defs/cc/whitelists/parse_headers_and_layering_check:"
           + ALLOWED_LAYERING_CHECK_FEATURES_ALLOWLIST;

   public static final String FDO_OPTIMIZE_ATTR = ":fdo_optimize";
   public static final String FDO_PROFILE_ATTR = ":fdo_profile";
   public static final String CSFDO_PROFILE_ATTR = ":csfdo_profile";
   public static final String XFDO_PROFILE_ATTR = ":xfdo_profile";

   @Override
   public RuleClass build(RuleClass.Builder builder, RuleDefinitionEnvironment env) {
     return builder
         .requiresConfigurationFragments(CppConfiguration.class, PlatformConfiguration.class)
         .advertiseProvider(TemplateVariableInfo.class)
         .add(attr("output_licenses", LICENSE))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(all_files) -->
         Collection of all cc_toolchain artifacts. These artifacts will be added as inputs to all
         rules_cc related actions (with the exception of actions that are using more precise sets of
         artifacts from attributes below). Bazel assumes that <code>all_files</code> is a superset
         of all other artifact-providing attributes (e.g. linkstamp compilation needs both compile
         and link files, so it takes <code>all_files</code>).

         <p>
         This is what <code>cc_toolchain.files</code> contains, and this is used by all Starlark
         rules using C++ toolchain.</p>
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("all_files", LABEL)
                 .legacyAllowAnyFileType()
                 .cfg(new CcToolchainInputsTransitionFactory())
                 .mandatory())
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(compiler_files) -->
         Collection of all cc_toolchain artifacts required for compile actions.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("compiler_files", LABEL)
                 .legacyAllowAnyFileType()
                 .cfg(new CcToolchainInputsTransitionFactory())
                 .mandatory())
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(compiler_files_without_includes) -->
         Collection of all cc_toolchain artifacts required for compile actions in case when
         input discovery is supported (currently Google-only).
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("compiler_files_without_includes", LABEL)
                 .legacyAllowAnyFileType()
                 .cfg(new CcToolchainInputsTransitionFactory()))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(strip_files) -->
         Collection of all cc_toolchain artifacts required for strip actions.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("strip_files", LABEL)
                 .legacyAllowAnyFileType()
                 .cfg(new CcToolchainInputsTransitionFactory())
                 .mandatory())
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(objcopy_files) -->
         Collection of all cc_toolchain artifacts required for objcopy actions.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("objcopy_files", LABEL)
                 .legacyAllowAnyFileType()
                 .cfg(new CcToolchainInputsTransitionFactory())
                 .mandatory())
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(as_files) -->
         <p>Collection of all cc_toolchain artifacts required for assembly actions.</p>
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("as_files", LABEL)
                 .legacyAllowAnyFileType()
                 .cfg(new CcToolchainInputsTransitionFactory()))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(ar_files) -->
         <p>Collection of all cc_toolchain artifacts required for archiving actions.</p>
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("ar_files", LABEL)
                 .legacyAllowAnyFileType()
                 .cfg(new CcToolchainInputsTransitionFactory()))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(linker_files) -->
         Collection of all cc_toolchain artifacts required for linking actions.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("linker_files", LABEL)
                 .legacyAllowAnyFileType()
                 .cfg(new CcToolchainInputsTransitionFactory())
                 .mandatory())
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(dwp_files) -->
         Collection of all cc_toolchain artifacts required for dwp actions.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("dwp_files", LABEL)
                 .legacyAllowAnyFileType()
                 .cfg(new CcToolchainInputsTransitionFactory())
                 .mandatory())
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(coverage_files) -->
         Collection of all cc_toolchain artifacts required for coverage actions. If not specified,
         all_files are used.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("coverage_files", LABEL)
                 .legacyAllowAnyFileType()
                 .cfg(new CcToolchainInputsTransitionFactory()))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(static_runtime_lib) -->
         Static library artifact for the C++ runtime library (e.g. libstdc++.a).

         <p>This will be used when 'static_link_cpp_runtimes' feature is enabled, and we're linking
         dependencies statically.</p>
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("static_runtime_lib", LABEL)
                 .legacyAllowAnyFileType()
                 // Should be in the target configuration
                 .cfg(NoTransition.createFactory()))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(dynamic_runtime_lib) -->
         Dynamic library artifact for the C++ runtime library (e.g. libstdc++.so).

         <p>This will be used when 'static_link_cpp_runtimes' feature is enabled, and we're linking
         dependencies dynamically.</p>
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("dynamic_runtime_lib", LABEL)
                 .legacyAllowAnyFileType()
                 // Should be in the target configuration
                 .cfg(NoTransition.createFactory()))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(module_map) -->
         Module map artifact to be used for modular builds.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("module_map", LABEL)
                 .legacyAllowAnyFileType()
                 // Should be in the target configuration
                 .cfg(NoTransition.createFactory()))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(supports_param_files) -->
         Set to True when cc_toolchain supports using param files for linking actions.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(attr("supports_param_files", BOOLEAN).value(true))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(supports_header_parsing) -->
         Set to True when cc_toolchain supports header parsing actions.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(attr("supports_header_parsing", BOOLEAN).value(false))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(exec_transition_for_inputs) -->
         Set to True to build all file inputs to cc_toolchain for the exec platform,
         instead of having no transition (i.e. target platform by default).
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(attr(CcToolchainInputsTransitionFactory.ATTR_NAME, BOOLEAN).value(true))
         // TODO(b/78578234): Make this the default and remove the late-bound versions.
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(libc_top) -->
         A collection of artifacts for libc passed as inputs to compile/linking actions.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("libc_top", LABEL)
                 .allowedFileTypes()
                 // Should be in the target configuration
                 .cfg(NoTransition.createFactory()))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(toolchain_identifier) -->
         The identifier used to match this cc_toolchain with the corresponding
         crosstool_config.toolchain.

         <p>
           Until issue <a href="https://github.com/bazelbuild/bazel/issues/5380">#5380</a> is fixed
           this is the recommended way of associating <code>cc_toolchain</code> with
           <code>CROSSTOOL.toolchain</code>. It will be replaced by the <code>toolchain_config</code>
           attribute (<a href="https://github.com/bazelbuild/bazel/issues/5380">#5380</a>).</p>
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr("toolchain_identifier", Type.STRING)
                 .nonconfigurable("Used in configuration creation")
                 .value(""))
         /* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(toolchain_config) -->
         The label of the rule providing <code>cc_toolchain_config_info</code>.
         <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
         .add(
             attr(TOOLCHAIN_CONFIG_ATTR, LABEL)
                 .allowedFileTypes()
                 .mandatoryProviders(CcToolchainConfigInfo.PROVIDER.id())
                 .mandatory()
                 // Should be in the target configuration
                 .cfg(NoTransition.createFactory()))
         .build();
   }

   @Override
   public Metadata getMetadata() {
     return RuleDefinition.Metadata.builder()
         .name("cc_toolchain")
         .ancestors(BaseRuleClasses.NativeBuildRule.class)
         .factoryClass(BaseRuleClasses.EmptyRuleConfiguredTargetFactory.class)
         .build();
   }
 }

 /*<!-- #BLAZE_RULE (NAME = cc_toolchain, TYPE = OTHER, FAMILY = C / C++) -->

 <p>Represents a C++ toolchain.</p>

 <p>
   This rule is responsible for:

   <ul>
     <li>
       Collecting all artifacts needed for C++ actions to run. This is done by
       attributes such as <code>all_files</code>, <code>compiler_files</code>,
       <code>linker_files</code>, or other attributes ending with <code>_files</code>). These are
       most commonly filegroups globbing all required files.
     </li>
     <li>
       Generating correct command lines for C++ actions. This is done using
       <code>CcToolchainConfigInfo</code> provider (details below).
     </li>
   </ul>
 </p>
 <p>
   Use <code>toolchain_config</code> attribute to configure the C++ toolchain.
   See also this
   <a href="https://bazel.build/docs/cc-toolchain-config-reference">
     page
   </a> for elaborate C++ toolchain configuration and toolchain selection documentation.
 </p>
 <p>
   Use <code>tags = ["manual"]</code> in order to prevent toolchains from being built and configured
   unnecessarily when invoking <code>bazel build //...</code>
 </p>
 <!-- #END_BLAZE_RULE -->*/
	// Copyright 2014 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.
	package com.google.devtools.build.lib.rules.cpp;

	import static com.google.devtools.build.lib.packages.Attribute.attr;
	import static com.google.devtools.build.lib.packages.BuildType.LABEL;
	import static com.google.devtools.build.lib.packages.BuildType.LICENSE;
	import static com.google.devtools.build.lib.packages.Type.BOOLEAN;

	import com.google.devtools.build.lib.analysis.BaseRuleClasses;
	import com.google.devtools.build.lib.analysis.PlatformConfiguration;
	import com.google.devtools.build.lib.analysis.RuleDefinition;
	import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
	import com.google.devtools.build.lib.analysis.TemplateVariableInfo;
	import com.google.devtools.build.lib.analysis.config.transitions.NoTransition;
	import com.google.devtools.build.lib.packages.RuleClass;
	import com.google.devtools.build.lib.packages.Type;

	/**
	* Rule definition for compiler definition.
	*/
	public final class CcToolchainRule implements RuleDefinition {

	public static final String TOOLCHAIN_CONFIG_ATTR = "toolchain_config";

	/** Default attribute name where rules store the reference to cc_toolchain */
	public static final String CC_TOOLCHAIN_DEFAULT_ATTRIBUTE_NAME = ":cc_toolchain";

	public static final String CC_TOOLCHAIN_DEFAULT_ATTRIBUTE_NAME_FOR_STARLARK = "$cc_toolchain";

	/** Default attribute name for the c++ toolchain type */
	public static final String CC_TOOLCHAIN_TYPE_ATTRIBUTE_NAME = "$cc_toolchain_type";

	public static final String ALLOWED_LAYERING_CHECK_FEATURES_ALLOWLIST =
	"disabling_parse_headers_and_layering_check_allowed";
	public static final String ALLOWED_LAYERING_CHECK_FEATURES_TARGET =
	"//tools/build_defs/cc/whitelists/parse_headers_and_layering_check:"
	+ ALLOWED_LAYERING_CHECK_FEATURES_ALLOWLIST;

	public static final String FDO_OPTIMIZE_ATTR = ":fdo_optimize";
	public static final String FDO_PROFILE_ATTR = ":fdo_profile";
	public static final String CSFDO_PROFILE_ATTR = ":csfdo_profile";
	public static final String XFDO_PROFILE_ATTR = ":xfdo_profile";

	@Override
	public RuleClass build(RuleClass.Builder builder, RuleDefinitionEnvironment env) {
	return builder
	.requiresConfigurationFragments(CppConfiguration.class, PlatformConfiguration.class)
	.advertiseProvider(TemplateVariableInfo.class)
	.add(attr("output_licenses", LICENSE))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(all_files) -->
	Collection of all cc_toolchain artifacts. These artifacts will be added as inputs to all
	rules_cc related actions (with the exception of actions that are using more precise sets of
	artifacts from attributes below). Bazel assumes that <code>all_files</code> is a superset
	of all other artifact-providing attributes (e.g. linkstamp compilation needs both compile
	and link files, so it takes <code>all_files</code>).

	<p>
	This is what <code>cc_toolchain.files</code> contains, and this is used by all Starlark
	rules using C++ toolchain.</p>
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("all_files", LABEL)
	.legacyAllowAnyFileType()
	.cfg(new CcToolchainInputsTransitionFactory())
	.mandatory())
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(compiler_files) -->
	Collection of all cc_toolchain artifacts required for compile actions.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("compiler_files", LABEL)
	.legacyAllowAnyFileType()
	.cfg(new CcToolchainInputsTransitionFactory())
	.mandatory())
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(compiler_files_without_includes) -->
	Collection of all cc_toolchain artifacts required for compile actions in case when
	input discovery is supported (currently Google-only).
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("compiler_files_without_includes", LABEL)
	.legacyAllowAnyFileType()
	.cfg(new CcToolchainInputsTransitionFactory()))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(strip_files) -->
	Collection of all cc_toolchain artifacts required for strip actions.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("strip_files", LABEL)
	.legacyAllowAnyFileType()
	.cfg(new CcToolchainInputsTransitionFactory())
	.mandatory())
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(objcopy_files) -->
	Collection of all cc_toolchain artifacts required for objcopy actions.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("objcopy_files", LABEL)
	.legacyAllowAnyFileType()
	.cfg(new CcToolchainInputsTransitionFactory())
	.mandatory())
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(as_files) -->
	<p>Collection of all cc_toolchain artifacts required for assembly actions.</p>
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("as_files", LABEL)
	.legacyAllowAnyFileType()
	.cfg(new CcToolchainInputsTransitionFactory()))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(ar_files) -->
	<p>Collection of all cc_toolchain artifacts required for archiving actions.</p>
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("ar_files", LABEL)
	.legacyAllowAnyFileType()
	.cfg(new CcToolchainInputsTransitionFactory()))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(linker_files) -->
	Collection of all cc_toolchain artifacts required for linking actions.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("linker_files", LABEL)
	.legacyAllowAnyFileType()
	.cfg(new CcToolchainInputsTransitionFactory())
	.mandatory())
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(dwp_files) -->
	Collection of all cc_toolchain artifacts required for dwp actions.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("dwp_files", LABEL)
	.legacyAllowAnyFileType()
	.cfg(new CcToolchainInputsTransitionFactory())
	.mandatory())
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(coverage_files) -->
	Collection of all cc_toolchain artifacts required for coverage actions. If not specified,
	all_files are used.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("coverage_files", LABEL)
	.legacyAllowAnyFileType()
	.cfg(new CcToolchainInputsTransitionFactory()))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(static_runtime_lib) -->
	Static library artifact for the C++ runtime library (e.g. libstdc++.a).

	<p>This will be used when 'static_link_cpp_runtimes' feature is enabled, and we're linking
	dependencies statically.</p>
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("static_runtime_lib", LABEL)
	.legacyAllowAnyFileType()
	// Should be in the target configuration
	.cfg(NoTransition.createFactory()))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(dynamic_runtime_lib) -->
	Dynamic library artifact for the C++ runtime library (e.g. libstdc++.so).

	<p>This will be used when 'static_link_cpp_runtimes' feature is enabled, and we're linking
	dependencies dynamically.</p>
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("dynamic_runtime_lib", LABEL)
	.legacyAllowAnyFileType()
	// Should be in the target configuration
	.cfg(NoTransition.createFactory()))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(module_map) -->
	Module map artifact to be used for modular builds.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("module_map", LABEL)
	.legacyAllowAnyFileType()
	// Should be in the target configuration
	.cfg(NoTransition.createFactory()))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(supports_param_files) -->
	Set to True when cc_toolchain supports using param files for linking actions.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(attr("supports_param_files", BOOLEAN).value(true))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(supports_header_parsing) -->
	Set to True when cc_toolchain supports header parsing actions.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(attr("supports_header_parsing", BOOLEAN).value(false))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(exec_transition_for_inputs) -->
	Set to True to build all file inputs to cc_toolchain for the exec platform,
	instead of having no transition (i.e. target platform by default).
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(attr(CcToolchainInputsTransitionFactory.ATTR_NAME, BOOLEAN).value(true))
	// TODO(b/78578234): Make this the default and remove the late-bound versions.
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(libc_top) -->
	A collection of artifacts for libc passed as inputs to compile/linking actions.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("libc_top", LABEL)
	.allowedFileTypes()
	// Should be in the target configuration
	.cfg(NoTransition.createFactory()))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(toolchain_identifier) -->
	The identifier used to match this cc_toolchain with the corresponding
	crosstool_config.toolchain.

	<p>
	Until issue <a href="https://github.com/bazelbuild/bazel/issues/5380">#5380</a> is fixed
	this is the recommended way of associating <code>cc_toolchain</code> with
	<code>CROSSTOOL.toolchain</code>. It will be replaced by the <code>toolchain_config</code>
	attribute (<a href="https://github.com/bazelbuild/bazel/issues/5380">#5380</a>).</p>
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr("toolchain_identifier", Type.STRING)
	.nonconfigurable("Used in configuration creation")
	.value(""))
	/* <!-- #BLAZE_RULE(cc_toolchain).ATTRIBUTE(toolchain_config) -->
	The label of the rule providing <code>cc_toolchain_config_info</code>.
	<!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
	.add(
	attr(TOOLCHAIN_CONFIG_ATTR, LABEL)
	.allowedFileTypes()
	.mandatoryProviders(CcToolchainConfigInfo.PROVIDER.id())
	.mandatory()
	// Should be in the target configuration
	.cfg(NoTransition.createFactory()))
	.build();
	}

	@Override
	public Metadata getMetadata() {
	return RuleDefinition.Metadata.builder()
	.name("cc_toolchain")
	.ancestors(BaseRuleClasses.NativeBuildRule.class)
	.factoryClass(BaseRuleClasses.EmptyRuleConfiguredTargetFactory.class)
	.build();
	}
	}

	/*<!-- #BLAZE_RULE (NAME = cc_toolchain, TYPE = OTHER, FAMILY = C / C++) -->

	<p>Represents a C++ toolchain.</p>

	<p>
	This rule is responsible for:

	<ul>
	<li>
	Collecting all artifacts needed for C++ actions to run. This is done by
	attributes such as <code>all_files</code>, <code>compiler_files</code>,
	<code>linker_files</code>, or other attributes ending with <code>_files</code>). These are
	most commonly filegroups globbing all required files.
	</li>
	<li>
	Generating correct command lines for C++ actions. This is done using
	<code>CcToolchainConfigInfo</code> provider (details below).
	</li>
	</ul>
	</p>
	<p>
	Use <code>toolchain_config</code> attribute to configure the C++ toolchain.
	See also this
	<a href="https://bazel.build/docs/cc-toolchain-config-reference">
	page
	</a> for elaborate C++ toolchain configuration and toolchain selection documentation.
	</p>
	<p>
	Use <code>tags = ["manual"]</code> in order to prevent toolchains from being built and configured
	unnecessarily when invoking <code>bazel build //...</code>
	</p>
	<!-- #END_BLAZE_RULE -->*/