Error out when the STL label points to an undefined target when merging STL

and toolchain contexts.

--
PiperOrigin-RevId: 148104218
MOS_MIGRATED_REVID=148104218

1 files changed, 7 insertions, 1 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppHelper.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppHelper.java
index 8541778e59..befcb82e13 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppHelper.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppHelper.java
@@ -90,7 +90,13 @@ public class CppHelper {
         // TODO(bazel-team): Clean this up.
         contextBuilder.addSystemIncludeDir(
             stl.getLabel().getPackageIdentifier().getPathUnderExecRoot().getRelative("gcc3"));
-        contextBuilder.mergeDependentContext(stl.getProvider(CppCompilationContext.class));
+        CppCompilationContext provider = stl.getProvider(CppCompilationContext.class);
+        if (provider == null) {
+          ruleContext.ruleError("Unable to merge the STL '" + stl.getLabel()
+              + "' and toolchain contexts");
+          return;
+        }
+        contextBuilder.mergeDependentContext(provider);
       }
     }
     if (toolchain != null) {