1 files changed, 11 insertions, 1 deletions
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 97a5d0e9d28..f0b17523682 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -3089,7 +3089,17 @@ class ASTIdentifierTableTrait {
   }
 
   SubmoduleID getSubmoduleID(MacroDirective *MD) {
-    return Writer.inferSubmoduleIDFromLocation(MD->getLocation());
+    if (MD->getLocation().isValid())
+      return Writer.inferSubmoduleIDFromLocation(MD->getLocation());
+
+    // If we have no directive location, this macro was installed when
+    // finalizing the ASTReader.
+    if (DefMacroDirective *DefMD = dyn_cast<DefMacroDirective>(MD))
+      return DefMD->getInfo()->getOwningModuleID();
+
+    // Skip imports that only produce #undefs for now.
+    // FIXME: We should still re-export them!
+    return 0;
   }
 
 public: