Modules hide macro definitions by default, so that silly things like

include guards don't show up as macro definitions in every translation
unit that imports a module. Macro definitions can, however, be
exported with the intentionally-ugly #__export_macro__
directive. Implement this feature by not even bothering to serialize
non-exported macros to a module, because clients of that module need
not (should not) know that these macros even exist.

llvm-svn: 138943

1 files changed, 34 insertions, 0 deletions

diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 99383e4791b..c8fcc3e37d1 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -652,6 +652,9 @@ TryAgain:
     case tok::pp_unassert:
       //isExtension = true;  // FIXME: implement #unassert
       break;
+        
+    case tok::pp___export_macro__:
+      return HandleMacroExportDirective(Result);
     }
     break;
   }
@@ -1000,6 +1003,37 @@ void Preprocessor::HandleIdentSCCSDirective(Token &Tok) {
   }
 }
 
+/// \brief Handle a #__export_macro__ directive.
+void Preprocessor::HandleMacroExportDirective(Token &Tok) {
+  Token MacroNameTok;
+  ReadMacroName(MacroNameTok, 2);
+  
+  // Error reading macro name?  If so, diagnostic already issued.
+  if (MacroNameTok.is(tok::eod))
+    return;
+
+  // Check to see if this is the last token on the #__export_macro__ line.
+  CheckEndOfDirective("__export_macro__");
+
+  // Okay, we finally have a valid identifier to undef.
+  MacroInfo *MI = getMacroInfo(MacroNameTok.getIdentifierInfo());
+  
+  // If the macro is not defined, this is an error.
+  if (MI == 0) {
+    Diag(MacroNameTok, diag::err_pp_export_non_macro)
+      << MacroNameTok.getIdentifierInfo();
+    return;
+  }
+  
+  // Note that this macro has now been exported.
+  MI->setExportLocation(MacroNameTok.getLocation());
+  
+  // If this macro definition came from a PCH file, mark it
+  // as having changed since serialization.
+  if (MI->isFromAST())
+    MI->setChangedAfterLoad();
+}
+
 //===----------------------------------------------------------------------===//
 // Preprocessor Include Directive Handling.
 //===----------------------------------------------------------------------===//