Fix ABI tag (B <source-name>) handling in nested names and function names

In DemangleNestedName(), the previous code broke out of the parsing loop
when it saw 'B' (an ABI tag prefix), leaving the 'E' nested-name terminator
unconsumed and causing the remainder of the qualified name (e.g. constructor
C1) to be lost.

The fix: instead of breaking, consume all consecutive 'B <source-name>'
sequences inline, appending "[abi:tag]" to the last name segment, then
continue parsing the rest of the nested name normally. The m_lastName is
saved and restored so that a following C1/D1 ctor/dtor still resolves to
the class name rather than the ABI tag string.

In DemangleFunction(), the old ad-hoc 'B' handler (which only recognized
"cxx11" and set a wrong return type) is replaced with the same ABI-tag
loop, allowing correct return-type detection for constructors/destructors
with ABI-tagged names.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: plafosse

demangler/gnu3/demangle_gnu3.cpp

@@ -1818,7 +1818,6 @@ DemangledTypeNode DemangleGNU3::DemangleNestedName()
 	DemangledTypeNode newType;
 	bool base = false;
 	bool isTemplate = false;
-	bool hasB = false;
 	//[<CV-qualifiers>]
 	DemangleCVQualifiers(cnst, vltl, rstrct);
 
@@ -1837,11 +1836,6 @@ DemangledTypeNode DemangleGNU3::DemangleNestedName()
 
 	while (m_reader.Peek() != 'E')
 	{
-		if (m_reader.Peek() == 'B')
-		{
-			hasB = true;
-			break;
-		}
 		isTemplate = false;
 		substitute = true;
 		size_t startSize = m_templateSubstitute.size();
@@ -1886,6 +1880,23 @@ DemangledTypeNode DemangleGNU3::DemangleNestedName()
 			type.SetNTR(type.GetNTRClass(), newName);
 			type.SetHasTemplateArguments(false);
 		}
+		// Consume any ABI tags (B <source-name>) following this name component.
+		// These appear as suffixes on <unqualified-name> in the Itanium ABI:
+		//   <abi-tags> ::= <abi-tag> [<abi-tags>]
+		//   <abi-tag>  ::= B <source-name>
+		// We append them as "[abi:tag]" to the last name segment for display.
+		// Save/restore m_lastName so that a following C1/D1 ctor/dtor name
+		// still resolves to the class name, not the ABI tag string.
+		while (m_reader.Peek() == 'B')
+		{
+			m_reader.Consume();
+			string savedLastName = m_lastName;
+			string abiTag = DemangleSourceName();
+			m_lastName = savedLastName;
+			auto& segs = type.GetMutableTypeName();
+			if (!segs.empty())
+				segs.back() += "[abi:" + abiTag + "]";
+		}
 		if (substitute && m_reader.Peek() != 'E')
 		{
 			//Those template arguments were not the primary arguments so clear them from the sub listType
@@ -1897,8 +1908,7 @@ DemangledTypeNode DemangleGNU3::DemangleNestedName()
 		}
 		MyLogDebug("%s:: '%s'\n", __FUNCTION__, m_reader.GetRaw().c_str());
 	}
-	if (!hasB)
-		m_reader.Consume();
+	m_reader.Consume();
 
 	if (cnst || vltl || rstrct)
 	{
@@ -2426,18 +2436,20 @@ DemangledTypeNode DemangleGNU3::DemangleSymbol(QualifiedName& varName)
 		m_reader.Consume();
 		// TODO: If we get here we have a return type. What can we do with this info?
 	}
-	if (m_reader.Peek() == 'B')
+	// Consume any ABI tags on the function/data name (e.g. B5cxx11).
+	// For nested names these are already consumed inside DemangleNestedName();
+	// this handles the global-scope case.
+	while (m_reader.Peek() == 'B')
 	{
 		m_reader.Consume();
-		DemangledTypeNode t = DemangleUnqualifiedName();
-
-		if (t.GetString() == "cxx11")
-		{
-			static const QualifiedName stdCxx11StringName(vector<string>{"std", "cxx11", "string"});
-			returnType = CreateUnknownType(stdCxx11StringName);
-		}
-	}
-	else if (m_isOperatorOverload ||
+		string savedLastName = m_lastName;
+		string abiTag = DemangleSourceName();
+		m_lastName = savedLastName;
+		auto& segs = type.GetMutableTypeName();
+		if (!segs.empty())
+			segs.back() += "[abi:" + abiTag + "]";
+	}
+	if (m_isOperatorOverload ||
 		type.GetNameType() == ConstructorNameType ||
 		type.GetNameType() == DestructorNameType)
 	{