Reinstate r213348, reverted in r213395, with an additional bug fix and more

thorough tests.

Original commit message:

[modules] Fix macro hiding bug exposed if:

 * A submodule of module A is imported into module B
 * Another submodule of module A that is not imported into B exports a macro
 * Some submodule of module B also exports a definition of the macro, and
   happens to be the first submodule of B that imports module A.

In this case, we would incorrectly determine that A's macro redefines B's
macro, and so we don't need to re-export B's macro at all.

This happens with the 'assert' macro in an LLVM self-host. =(

llvm-svn: 213416

1 files changed, 17 insertions, 1 deletions

diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 97a5d0e9d28..9b44c54eb35 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -1900,6 +1900,12 @@ static bool shouldIgnoreMacro(MacroDirective *MD, bool IsModule,
       return true;
 
   if (IsModule) {
+    // Re-export any imported directives.
+    // FIXME: Also ensure we re-export imported #undef directives.
+    if (auto *DMD = dyn_cast<DefMacroDirective>(MD))
+      if (DMD->isImported())
+        return false;
+
     SourceLocation Loc = MD->getLocation();
     if (Loc.isInvalid())
       return true;
@@ -3089,7 +3095,17 @@ 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: