Change default behavior for cc_toolchain.compiler and cc_toolchain.libc for

platform-based toolchain selection to match legacy behavior.

This is a change over previous behavior in the platform case, which was to throw if either of those attributes is not present.  The default_toolchain field in CROSSTOOL gives a mapping from cc_toolchain.cpu values to toolchains - this map should be used with compiler and libc are not specified, as is currently the non-platforms, legacy behavior.

PiperOrigin-RevId: 176246316

2 files changed, 12 insertions, 20 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchain.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchain.java
index f7fc13e4dc..c66dd9378b 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchain.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchain.java
@@ -601,18 +601,21 @@ public class CcToolchain implements RuleConfiguredTargetFactory {
 
   private CToolchain getToolchainFromAttributes(
       RuleContext ruleContext, CppConfiguration cppConfiguration) throws RuleErrorException {
-    for (String requiredAttr : ImmutableList.of("cpu", "compiler", "libc")) {
-      if (ruleContext.attributes().get(requiredAttr, Type.STRING).isEmpty()) {
-        ruleContext.throwWithRuleError(
-            String.format(
-                "Using cc_toolchain target requires the attribute '%s' to be present.",
-                requiredAttr));
-      }
+    if (ruleContext.attributes().get("cpu", Type.STRING).isEmpty()) {
+      ruleContext.throwWithRuleError("Using cc_toolchain target requires the attribute 'cpu' "
+          + "to be present");
     }
 
+
     String cpu = ruleContext.attributes().get("cpu", Type.STRING);
     String compiler = ruleContext.attributes().get("compiler", Type.STRING);
+    if (compiler.isEmpty()) {
+      compiler = null;
+    }
     String libc = ruleContext.attributes().get("libc", Type.STRING);
+    if (libc.isEmpty()) {
+      libc = null;
+    }
     CrosstoolConfigurationIdentifier config =
         new CrosstoolConfigurationIdentifier(cpu, compiler, libc);
 
diff --git a/src/test/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSelectionTest.java b/src/test/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSelectionTest.java
index e0d92a4c1e..e6c453e28a 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSelectionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSelectionTest.java
@@ -26,7 +26,6 @@ import com.google.devtools.build.lib.analysis.util.ScratchAttributeWriter;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.packages.util.MockCcSupport;
 import com.google.devtools.build.lib.packages.util.MockPlatformSupport;
-import com.google.devtools.build.lib.testutil.MoreAsserts;
 import com.google.devtools.build.lib.testutil.TestConstants;
 import com.google.devtools.build.lib.view.config.crosstool.CrosstoolConfig.ToolPath;
 import java.util.List;
@@ -128,7 +127,7 @@ public class CcToolchainSelectionTest extends BuildViewTestCase {
   }
 
   @Test
-  public void testErrorForIncompleteCcToolchain() throws Exception {
+  public void testIncompleteCcToolchain() throws Exception {
     mockToolsConfig.create(
         "incomplete_toolchain/BUILD",
         "toolchain(",
@@ -156,17 +155,7 @@ public class CcToolchainSelectionTest extends BuildViewTestCase {
         "--experimental_platforms=//mock_platform:mock-piii-platform",
         "--extra_toolchains=//incomplete_toolchain:incomplete_toolchain_cc-compiler-piii");
 
-    AssertionError thrown =
-        MoreAsserts.expectThrows(
-            AssertionError.class,
-            () ->
-                ScratchAttributeWriter.fromLabelString(this, "cc_library", "//lib")
-                    .setList("srcs", "a.cc")
-                    .write());
-
-    assertThat(thrown)
-        .hasMessageThat()
-        .contains("Using cc_toolchain target requires the attribute 'compiler' to be present");
+    // should not throw.
   }
 
   @Test