[clang] Itanium mangler constructors

[urnathan]

Summary

The Itanium mangler constructors use both NSDMI and explicit member construction for default values. This is confusing.

*) Use NSDMIs wherever possible

*) Use forwarding ctor for the nesting case with an llvm::raw_null_ostream (and explicitly set NullOut flag in that ctor).

*) Copy the ModuleSubstitutions. This is a bug with no effect in the current mangling, but not in the newer mangling.

@ChuanquXi, the bug is possibly the cause of the crash you're encountering in the update module mangling patch. It would be good to be able to put a testcase in for that.

[ChuanqiXu]

LGTM. I would accept it after I am sure whether or not I could give the test case.

[urnathan]

In D119550#3318133, @ChuanqiXu wrote:

LGTM. I would accept it after I am sure whether or not I could give the test case.

Ok, let's give it a few days.

[ChuanqiXu]

Sorry I failed to give a reduced test. I believe this patch should be fine.

clang/lib/AST/ItaniumMangle.cpp

class CXXNameMangler {
   /// calculate ABI tags for the function return value or the variable type.
   /// Also it is required to avoid infinite recursion in some cases.
   bool DisableDerivedAbiTags = false;
 
   /// The "structor" is the top-level declaration being mangled, if
   /// that's not a template specialization; otherwise it's the pattern
   /// for that specialization.
   const NamedDecl *Structor;
-  unsigned StructorType;
+  unsigned StructorType = 0;
 
   /// The next substitution sequence number.
-  unsigned SeqID;
+  unsigned SeqID = 0;
 
   class FunctionTypeDepthState {
     unsigned Bits;
 
     enum { InResultTypeMask = 1 };
 
   public:
     FunctionTypeDepthState() : Bits(0) {}
class CXXNameMangler {
   llvm::DenseMap<uintptr_t, unsigned> Substitutions;
   llvm::DenseMap<StringRef, unsigned> ModuleSubstitutions;
 
   ASTContext &getASTContext() const { return Context.getASTContext(); }
 
 public:
   CXXNameMangler(ItaniumMangleContextImpl &C, raw_ostream &Out_,
                  const NamedDecl *D = nullptr, bool NullOut_ = false)
-    : Context(C), Out(Out_), NullOut(NullOut_),  Structor(getStructor(D)),
-      StructorType(0), SeqID(0), AbiTagsRoot(AbiTags) {
+      : Context(C), Out(Out_), NullOut(NullOut_), Structor(getStructor(D)),
+        AbiTagsRoot(AbiTags) {
     // These can't be mangled without a ctor type or dtor type.
     assert(!D || (!isa<CXXDestructorDecl>(D) &&
                   !isa<CXXConstructorDecl>(D)));
   }
   CXXNameMangler(ItaniumMangleContextImpl &C, raw_ostream &Out_,
                  const CXXConstructorDecl *D, CXXCtorType Type)
       : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(Type),
-      SeqID(0), AbiTagsRoot(AbiTags) { }
+        AbiTagsRoot(AbiTags) {}
   CXXNameMangler(ItaniumMangleContextImpl &C, raw_ostream &Out_,
                  const CXXDestructorDecl *D, CXXDtorType Type)
       : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(Type),
-      SeqID(0), AbiTagsRoot(AbiTags) { }
+        AbiTagsRoot(AbiTags) {}
 
   CXXNameMangler(CXXNameMangler &Outer, raw_ostream &Out_)
-      : Context(Outer.Context), Out(Out_), NullOut(false),
-        Structor(Outer.Structor), StructorType(Outer.StructorType),
-        SeqID(Outer.SeqID), FunctionTypeDepth(Outer.FunctionTypeDepth),
-        AbiTagsRoot(AbiTags), Substitutions(Outer.Substitutions) {}
+      : Context(Outer.Context), Out(Out_), Structor(Outer.Structor),
+        StructorType(Outer.StructorType), SeqID(Outer.SeqID),
+        FunctionTypeDepth(Outer.FunctionTypeDepth), AbiTagsRoot(AbiTags),
+        Substitutions(Outer.Substitutions),
+        ModuleSubstitutions(Outer.ModuleSubstitutions) {}
 
   CXXNameMangler(CXXNameMangler &Outer, llvm::raw_null_ostream &Out_)
-      : Context(Outer.Context), Out(Out_), NullOut(true),
-        Structor(Outer.Structor), StructorType(Outer.StructorType),
-        SeqID(Outer.SeqID), FunctionTypeDepth(Outer.FunctionTypeDepth),
-        AbiTagsRoot(AbiTags), Substitutions(Outer.Substitutions) {}
+      : CXXNameMangler(Outer, (raw_ostream &)Out_) {
+    NullOut = true;
+  }
 
   raw_ostream &getStream() { return Out; }
 
   void disableDerivedAbiTags() { DisableDerivedAbiTags = true; }
   static bool shouldHaveAbiTags(ItaniumMangleContextImpl &C, const VarDecl *VD);
 
   void mangle(GlobalDecl GD);
   void mangleCallOffset(int64_t NonVirtual, int64_t Virtual);