MS ABI: Mangle null pointer-to-member-functions compatibly

Summary:
Previously, we would mangle nullptr pointer-to-member-functions in class
templates with a mangling we invented because contemporary versions of
MSVC would crash when trying to compile such code.

However, VS "14" can successfully compile these sorts of template
instantiations.  This commit updates our mangling to be compatible with
theirs.

Reviewers: rnk

Reviewed By: rnk

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4059

llvm-svn: 210637

1 files changed, 25 insertions, 24 deletions

diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index a02402580d9..481ed44347e 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -495,18 +495,9 @@ MicrosoftCXXNameMangler::mangleMemberFunctionPointer(const CXXRecordDecl *RD,
   //                           ::= $H? <name> <number>
   //                           ::= $I? <name> <number> <number>
   //                           ::= $J? <name> <number> <number> <number>
-  //                           ::= $0A@
 
   MSInheritanceAttr::Spelling IM = RD->getMSInheritanceModel();
 
-  // The null member function pointer is $0A@ in function templates and crashes
-  // MSVC when used in class templates, so we don't know what they really look
-  // like.
-  if (!MD) {
-    Out << "$0A@";
-    return;
-  }
-
   char Code = '\0';
   switch (IM) {
   case MSInheritanceAttr::Keyword_single_inheritance:      Code = '1'; break;
@@ -515,28 +506,38 @@ MicrosoftCXXNameMangler::mangleMemberFunctionPointer(const CXXRecordDecl *RD,
   case MSInheritanceAttr::Keyword_unspecified_inheritance: Code = 'J'; break;
   }
 
-  Out << '$' << Code << '?';
-
   // If non-virtual, mangle the name.  If virtual, mangle as a virtual memptr
   // thunk.
   uint64_t NVOffset = 0;
   uint64_t VBTableOffset = 0;
   uint64_t VBPtrOffset = 0;
-  if (MD->isVirtual()) {
-    MicrosoftVTableContext *VTContext =
-        cast<MicrosoftVTableContext>(getASTContext().getVTableContext());
-    const MicrosoftVTableContext::MethodVFTableLocation &ML =
-        VTContext->getMethodVFTableLocation(GlobalDecl(MD));
-    mangleVirtualMemPtrThunk(MD, ML);
-    NVOffset = ML.VFPtrOffset.getQuantity();
-    VBTableOffset = ML.VBTableIndex * 4;
-    if (ML.VBase) {
-      const ASTRecordLayout &Layout = getASTContext().getASTRecordLayout(RD);
-      VBPtrOffset = Layout.getVBPtrOffset().getQuantity();
+  if (MD) {
+    Out << '$' << Code << '?';
+    if (MD->isVirtual()) {
+      MicrosoftVTableContext *VTContext =
+          cast<MicrosoftVTableContext>(getASTContext().getVTableContext());
+      const MicrosoftVTableContext::MethodVFTableLocation &ML =
+          VTContext->getMethodVFTableLocation(GlobalDecl(MD));
+      mangleVirtualMemPtrThunk(MD, ML);
+      NVOffset = ML.VFPtrOffset.getQuantity();
+      VBTableOffset = ML.VBTableIndex * 4;
+      if (ML.VBase) {
+        const ASTRecordLayout &Layout = getASTContext().getASTRecordLayout(RD);
+        VBPtrOffset = Layout.getVBPtrOffset().getQuantity();
+      }
+    } else {
+      mangleName(MD);
+      mangleFunctionEncoding(MD);
     }
   } else {
-    mangleName(MD);
-    mangleFunctionEncoding(MD);
+    // Null single inheritance member functions are encoded as a simple nullptr.
+    if (IM == MSInheritanceAttr::Keyword_single_inheritance) {
+      Out << "$0A@";
+      return;
+    }
+    if (IM == MSInheritanceAttr::Keyword_unspecified_inheritance)
+      VBTableOffset = -1;
+    Out << '$' << Code;
   }
 
   if (MSInheritanceAttr::hasNVOffsetField(/*IsMemberFunction=*/true, IM))