Handle explicit GNU template parameter pack declarations

Parse Ty, Tn, Tt, and Tp declarations before their template argument,
preserving the argument or pack's template substitution slot. Apply the
existing nesting limit to recursive declarations and qualified arguments.

Author: plafosse

demangler/gnu3/demangle_gnu3.cpp

@@ -2236,8 +2236,39 @@ bool DemangleGNU3::AppendTemplateParamPackExpansion(ParamList& params, NodeRef e
 }
 
 
+void DemangleGNU3::DemangleTemplateParamDecl()
+{
+	NestingGuard nestingGuard(m_nestingDepth);
+	// <template-param-decl> ::= Ty                           # type parameter
+	//                       ::= Tn <type>                    # non-type parameter
+	//                       ::= Tt <template-param-decl>* E  # template parameter
+	//                       ::= Tp <template-param-decl>     # parameter pack
+	if (!m_reader.ConsumeIf('T'))
+		throw DemangleException();
+
+	switch (m_reader.Read())
+	{
+	case 'y':
+		return;
+	case 'n':
+		DemangleType();
+		return;
+	case 't':
+		while (!m_reader.ConsumeIf('E'))
+			DemangleTemplateParamDecl();
+		return;
+	case 'p':
+		DemangleTemplateParamDecl();
+		return;
+	default:
+		throw DemangleException();
+	}
+}
+
+
 bool DemangleGNU3::DemangleTemplateArg(ParamList& args, bool* hadNonTypeArg)
 {
+	NestingGuard nestingGuard(m_nestingDepth);
 	DemangledTypeNode tmp;
 	NodeRef tmpRef;
 	bool tmpValid = false;
@@ -2294,18 +2325,15 @@ bool DemangleGNU3::DemangleTemplateArg(ParamList& args, bool* hadNonTypeArg)
 		break;
 	}
 	case 'T':
-		if (m_reader.ConsumeIf('n'))
+		if (const char kind = m_reader.PeekOr(); kind == 'y' || kind == 'n' || kind == 't' || kind == 'p')
 		{
 			// <template-arg> ::= <template-param-decl> <template-arg>
-			// <template-param-decl> ::= Tn <type>  # non-type parameter
-			//
-			// The declaration names a synthetic non-type template parameter
-			// for the following argument. Binary Ninja does not print those
-			// synthetic parameter names, so consume the declaration type and
-			// keep only the actual following template argument.
+			// Only the following argument contributes to the printed name and
+			// template substitution table; the declaration describes its parameter.
+			m_reader.UnRead();
 			topLevel = m_topLevel;
 			m_topLevel = false;
-			DemangleType();
+			DemangleTemplateParamDecl();
 			m_topLevel = topLevel;
 			return DemangleTemplateArg(args, hadNonTypeArg);
 		}

demangler/gnu3/demangle_gnu3.h

@@ -146,6 +146,7 @@ class DemangleGNU3
 	void DemangleCVQualifiers(bool& cnst, bool& vltl, bool& rstrct);
 	DemangledTypeNode DemangleSubstitution(NodeRef* outTypeRef = nullptr);
 	DemangledTypeNode DemangleTemplateSubstitution(NodeRef* outTypeRef = nullptr);
+	void DemangleTemplateParamDecl();
 	bool DemangleTemplateArg(ParamList& args, bool* hadNonTypeArg = nullptr);
 	void DemangleTemplateArgs(ParamList& args, bool* hadNonTypeArg = nullptr);
 	DemangledTypeNode DemangleFunction(bool cnst, bool vltl);