[PATCH] [-cxx-abi microsoft] Mangle TemplateArgument::Declaration correctly for member pointers

[David Majnemer]

================
Comment at: lib/AST/MicrosoftMangle.cpp:891
@@ +890,3 @@
+               getASTContext().getCharWidth();
+      mangleIntegerLiteral(Offset, false);
+    } else
----------------
Reid Kleckner wrote:
> There's a fair amount of complexity in member pointers.
> - Can I mangle in a null data memptr here?
> - The null representation is different between standard layout records (-1) and other records (0).
> - Can I mangle a field from a base class that is not at offset 0?
> 
> All this is currently handled in CodeGen/MicrosoftCXXABI.cpp, which this AST code can't depend on.  We could raise some parts of it up into the AST CXXABI if needed.
- Yes.
- null data memptr get's mangled like -1 for standard layout records and 0 for other records.
- Yes:
```
struct base1 {
  int thing;
  virtual int fun();
};      
struct base2 : virtual public base1 {
  int thing;
  virtual int fun2();
};
struct record : public base2, virtual public base1 {
  int first;
  int second;
  virtual int fun3();
};

template <int record::*>
struct type2 {};
type2<(int record::*)(&base2::thing)> memptr4;
type2<(int record::*)(&base1::thing)> memptr5;
```
get's mangled like so:
```
struct type2<{8,0}> memptr4
struct type2<{4,4}> memptr5
```

Note that clang **refuses** to do anything with this C++ code.


http://llvm-reviews.chandlerc.com/D1323