Add --experimental_enable_cc_toolchain_label_from_crosstool_proto flag for disabling relying on CROSSTOOL file in order to select the cc_toolchain label

CROSSTOOL file should not have any influence over selection of the cc_toolchain label. Ultimately the information that CROSSTOOL offers will be rerouted through an attribute of cc_toolchain.

RELNOTES: None.
PiperOrigin-RevId: 205651369

2 files changed, 26 insertions, 7 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfigurationLoader.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfigurationLoader.java
index a427752411..37d033794e 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfigurationLoader.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfigurationLoader.java
@@ -183,6 +183,13 @@ public class CppConfigurationLoader implements ConfigurationFragmentFactory {
           NonconfigurableAttributeMapper.of(ccToolchainSuite)
               .get("toolchains", BuildType.LABEL_DICT_UNARY);
       ccToolchainLabel = toolchains.get(key);
+      String errorMessage =
+          String.format(
+              "cc_toolchain_suite '%s' does not contain a toolchain for CPU '%s'",
+              crosstoolTopLabel, desiredCpu);
+      if (cppOptions.cppCompiler != null) {
+        errorMessage = errorMessage + " and compiler " + cppOptions.cppCompiler;
+      }
       if (ccToolchainLabel == null) {
         // If the cc_toolchain_suite does not contain entry for --cpu|--compiler (or only --cpu if
         // --compiler is not present) we select the toolchain by looping through all the toolchains
@@ -193,15 +200,18 @@ public class CppConfigurationLoader implements ConfigurationFragmentFactory {
             CrosstoolConfigurationLoader.selectToolchain(
                 file.getProto(), options, cpuTransformer.getTransformer());
         ccToolchainLabel = toolchains.get(toolchain.getTargetCpu() + "|" + toolchain.getCompiler());
+        if (!cppOptions.enableCcToolchainFromCrosstool) {
+          throw new InvalidConfigurationException(
+              errorMessage
+                  + String.format(
+                      ", you may want to add an entry for '%s|%s' into toolchains and "
+                          + "toolchain_identifier '%s' into the corresponding cc_toolchain rule.",
+                      toolchain.getTargetCpu(),
+                      toolchain.getCompiler(),
+                      toolchain.getToolchainIdentifier()));
+        }
       }
       if (ccToolchainLabel == null) {
-        String errorMessage =
-            String.format(
-                "cc_toolchain_suite '%s' does not contain a toolchain for CPU '%s'",
-                crosstoolTopLabel, desiredCpu);
-        if (cppOptions.cppCompiler != null) {
-          errorMessage = errorMessage + " and compiler " + cppOptions.cppCompiler;
-        }
         throw new InvalidConfigurationException(errorMessage);
       }
     } else {
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java
index 49a11a16f4..4e4e863b29 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java
@@ -862,6 +862,15 @@ public class CppOptions extends FragmentOptions {
               + "crosstool variable.")
   public boolean enableLinkoptsInUserLinkFlags;
 
+  @Option(
+      name = "experimental_enable_cc_toolchain_label_from_crosstool_proto",
+      defaultValue = "true",
+      documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
+      effectTags = {OptionEffectTag.LOADING_AND_ANALYSIS, OptionEffectTag.EAGERNESS_TO_EXIT},
+      metadataTags = {OptionMetadataTag.EXPERIMENTAL},
+      help = "If false, Bazel will not use the CROSSTOOL file to select the cc_toolchain label.")
+  public boolean enableCcToolchainFromCrosstool;
+
   @Override
   public FragmentOptions getHost() {
     CppOptions host = (CppOptions) getDefault();