Conditionally set the default crosstool based on the major revision by binding //external:android/crosstool to an alias in the NDK BUILD file.

This does not change existing behavior until r17 support is released.

https://github.com/bazelbuild/bazel/issues/4742

RELNOTES: None.
PiperOrigin-RevId: 189195669

4 files changed, 33 insertions, 18 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/android/AndroidNdkRepositoryFunction.java b/src/main/java/com/google/devtools/build/lib/bazel/rules/android/AndroidNdkRepositoryFunction.java
index bbdefada8a..cf61da68b9 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/android/AndroidNdkRepositoryFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/rules/android/AndroidNdkRepositoryFunction.java
@@ -27,6 +27,8 @@ import com.google.devtools.build.lib.bazel.rules.android.ndkcrosstools.NdkPaths;
 import com.google.devtools.build.lib.bazel.rules.android.ndkcrosstools.NdkRelease;
 import com.google.devtools.build.lib.bazel.rules.android.ndkcrosstools.StlImpl;
 import com.google.devtools.build.lib.bazel.rules.android.ndkcrosstools.StlImpls;
+import com.google.devtools.build.lib.bazel.rules.android.ndkcrosstools.StlImpls.GnuLibStdCppStlImpl;
+import com.google.devtools.build.lib.bazel.rules.android.ndkcrosstools.StlImpls.LibCppStlImpl;
 import com.google.devtools.build.lib.events.Event;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.rules.repository.RepositoryDirectoryValue;
@@ -219,7 +221,9 @@ public class AndroidNdkRepositoryFunction extends AndroidRepositoryFunction {
       throw new RepositoryFunctionException(new IOException(e), Transience.PERSISTENT);
     }
 
-    String buildFile = createBuildFile(ruleName, crosstoolsAndStls.build());
+    String defaultCrosstool = getDefaultCrosstool(ndkRelease.majorRevision);
+
+    String buildFile = createBuildFile(ruleName, defaultCrosstool, crosstoolsAndStls.build());
     writeBuildFile(outputDirectory, buildFile);
     return RepositoryDirectoryValue.builder().setPath(outputDirectory);
   }
@@ -229,12 +233,18 @@ public class AndroidNdkRepositoryFunction extends AndroidRepositoryFunction {
     return AndroidNdkRepositoryRule.class;
   }
 
+  private static String getDefaultCrosstool(Integer majorRevision) {
+    // From NDK 17, libc++ replaces gnu-libstdc++ as the default STL.
+    return majorRevision <= 16 ? GnuLibStdCppStlImpl.NAME : LibCppStlImpl.NAME;
+  }
+
   private static PathFragment getAndroidNdkHomeEnvironmentVar(
       Path workspace, Map<String, String> env) {
     return workspace.getRelative(PathFragment.create(env.get(PATH_ENV_VAR))).asFragment();
   }
 
-  private static String createBuildFile(String ruleName, List<CrosstoolStlPair> crosstools) {
+  private static String createBuildFile(
+      String ruleName, String defaultCrosstool, List<CrosstoolStlPair> crosstools) {
 
     String buildFileTemplate = getTemplate("android_ndk_build_file_template.txt");
     String ccToolchainSuiteTemplate = getTemplate("android_ndk_cc_toolchain_suite_template.txt");
@@ -286,6 +296,7 @@ public class AndroidNdkRepositoryFunction extends AndroidRepositoryFunction {
 
     return buildFileTemplate
         .replace("%ruleName%", ruleName)
+        .replace("%defaultCrosstool%", "//:toolchain-" + defaultCrosstool)
         .replace("%ccToolchainSuites%", ccToolchainSuites)
         .replace("%ccToolchainRules%", ccToolchainRules)
         .replace("%stlFilegroups%", stlFilegroups)
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/android/AndroidNdkRepositoryRule.java b/src/main/java/com/google/devtools/build/lib/bazel/rules/android/AndroidNdkRepositoryRule.java
index c2a5be5f92..7d3088029c 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/android/AndroidNdkRepositoryRule.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/rules/android/AndroidNdkRepositoryRule.java
@@ -21,7 +21,6 @@ import com.google.common.base.Function;
 import com.google.common.collect.ImmutableMap;
 import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
-import com.google.devtools.build.lib.bazel.rules.android.ndkcrosstools.StlImpls;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleClass;
@@ -38,16 +37,12 @@ public class AndroidNdkRepositoryRule implements RuleDefinition {
   public static final String NAME = "android_ndk_repository";
 
   private static final Function<? super Rule, Map<String, Label>> BINDINGS_FUNCTION =
-      rule -> {
-        String defaultToolchainName =
-            AndroidNdkRepositoryFunction.createToolchainName(StlImpls.DEFAULT_STL_NAME);
-
-        return ImmutableMap.of(
-            "android/crosstool",
-            Label.parseAbsoluteUnchecked("@" + rule.getName() + "//:" + defaultToolchainName),
-            "android_ndk_for_testing",
-            Label.parseAbsoluteUnchecked("@" + rule.getName() + "//:files"));
-      };
+      rule ->
+          ImmutableMap.of(
+              "android/crosstool",
+              Label.parseAbsoluteUnchecked("@" + rule.getName() + "//:default_crosstool"),
+              "android_ndk_for_testing",
+              Label.parseAbsoluteUnchecked("@" + rule.getName() + "//:files"));
 
   @Override
   public RuleClass build(Builder builder, RuleDefinitionEnvironment environment) {
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/android/android_ndk_build_file_template.txt b/src/main/java/com/google/devtools/build/lib/bazel/rules/android/android_ndk_build_file_template.txt
index eb2f818e0a..6612d27890 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/android/android_ndk_build_file_template.txt
+++ b/src/main/java/com/google/devtools/build/lib/bazel/rules/android/android_ndk_build_file_template.txt
@@ -27,6 +27,11 @@ cc_library(
     srcs = [],
 )
 
+alias(
+    name = "default_crosstool",
+    actual = "%defaultCrosstool%",
+)
+
 ################################################################
 # cc toolchain suite rules (one for each STL in the NDK)
 ################################################################
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/android/ndkcrosstools/StlImpls.java b/src/main/java/com/google/devtools/build/lib/bazel/rules/android/ndkcrosstools/StlImpls.java
index 0508b7c7c5..dc651e5e18 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/android/ndkcrosstools/StlImpls.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/rules/android/ndkcrosstools/StlImpls.java
@@ -24,14 +24,14 @@ import java.util.List;
  */
 public final class StlImpls {
 
-  public static final String DEFAULT_STL_NAME = "gnu-libstdcpp";
-  
   private StlImpls() {}
   
   public static class GnuLibStdCppStlImpl extends StlImpl {
 
+    public static final String NAME = "gnu-libstdcpp";
+
     public GnuLibStdCppStlImpl(NdkPaths ndkPaths) {
-      super(DEFAULT_STL_NAME, ndkPaths);
+      super(NAME, ndkPaths);
     }
 
     @Override
@@ -44,8 +44,10 @@ public final class StlImpls {
 
   public static class LibCppStlImpl extends StlImpl {
 
+    public static final String NAME = "libcpp";
+
     public LibCppStlImpl(NdkPaths ndkPaths) {
-      super("libcpp", ndkPaths);
+      super(NAME, ndkPaths);
     }
 
     @Override
@@ -58,8 +60,10 @@ public final class StlImpls {
 
   public static class StlPortStlImpl extends StlImpl {
 
+    public static final String NAME = "stlport";
+
     public StlPortStlImpl(NdkPaths ndkPaths) {
-      super("stlport", ndkPaths);
+      super(NAME, ndkPaths);
     }
 
     @Override