[modules] Fix incorrect diagnostic mapping computation when a module changes

diagnostic settings using _Pragma within a macro.

The AST writer had previously been assuming that all diagnostic state
transitions would occur within a FileID corresponding to a file. When a
diagnostic state change occured within a macro, it was unable to form a
location for that state change and would instead corrupt the diagnostic state
of the "root" node (and thus that of the main compilation).

Also introduce a "#pragma clang __debug diag_mapping" debugging utility
that I added to track this issue down.

llvm-svn: 324695

1 files changed, 14 insertions, 0 deletions

diff --git a/clang/lib/Lex/Pragma.cpp b/clang/lib/Lex/Pragma.cpp
index b9be03f4f20..db32e452d07 100644
--- a/clang/lib/Lex/Pragma.cpp
+++ b/clang/lib/Lex/Pragma.cpp
@@ -1053,6 +1053,20 @@ struct PragmaDebugHandler : public PragmaHandler {
         PP.Diag(Identifier, diag::warn_pragma_debug_missing_argument)
             << II->getName();
       }
+    } else if (II->isStr("diag_mapping")) {
+      Token DiagName;
+      PP.LexUnexpandedToken(DiagName);
+      if (DiagName.is(tok::eod))
+        PP.getDiagnostics().dump();
+      else if (DiagName.is(tok::string_literal) && !DiagName.hasUDSuffix()) {
+        StringLiteralParser Literal(DiagName, PP);
+        if (Literal.hadError)
+          return;
+        PP.getDiagnostics().dump(Literal.GetString());
+      } else {
+        PP.Diag(DiagName, diag::warn_pragma_debug_missing_argument)
+            << II->getName();
+      }
     } else if (II->isStr("llvm_fatal_error")) {
       llvm::report_fatal_error("#pragma clang __debug llvm_fatal_error");
     } else if (II->isStr("llvm_unreachable")) {