Provide the correct mangling and linkage for certain unnamed nested classes.

This corrects the mangling and linkage of classes (& their member functions) in
cases like this:

  struct foo {
    struct {
      void func() { ... }
    } x;
  };

we were accidentally giving this nested unnamed struct 'no' linkage where it
should've had the linkage of the outer class. The mangling was incorrecty too,
mangling as TU-wide unnamed type mangling of $_X rather than class-scoped
mangling of UtX_.

This also fixes -Wunused-member-function which would incorrectly diagnose
'func' as unused due to it having no linkage & thus appearing to be TU-local
when in fact it might be correctly used in another TU.

Similar mangling should be applied to function local classes in similar cases
but I've deferred that for a subsequent patch.

Review/discussion by Richard Smith, John McCall, & especially Eli Friedman.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167906 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index 851944a42b..fc61d88bd9 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -1117,6 +1117,18 @@ void CXXNameMangler::mangleUnqualifiedName(const NamedDecl *ND,
         break;
       }
     }
+
+    int UnnamedMangle = Context.getASTContext().getUnnamedTagManglingNumber(TD);
+    if (UnnamedMangle != -1) {
+      Out << "Ut";
+      if (UnnamedMangle != 0)
+        Out << llvm::utostr(UnnamedMangle - 1);
+      Out << '_';
+      break;
+    }
+
+    //assert(cast<RecordDecl>(RD)->isAnonymousStructOrUnion() && "Don't mangle unnamed things as "
+    //  "anonymous things");
         
     // Get a unique id for the anonymous struct.
     uint64_t AnonStructId = Context.getAnonymousStructId(TD);