Make FamilyBase ID generator function non-inline

Previously the function body was defined inline in the class body. For some toolchains (particularly discovered with LLVM on MinGW), different dynamic libraries call into different definitions of the function. This can lead to the same IDs being used even for different types, which can lead to issues and potentially crashes. This commit moves it to the CPP file so that all binaries call into the same function exported by the RmlUi library.

This commit does not change the fact that different binaries can still produce different IDs for the same type. However, that situation can generally be handled safely.

Include/RmlUi/Core/Traits.h

@@ -74,18 +74,14 @@ enum class FamilyId : int {};
 
 class RMLUICORE_API FamilyBase {
 protected:
-	static int GetNewId()
-	{
-		static int id = 0;
-		return id++;
-	}
+	static int GetNewId();
 };
 
 template <typename T>
 class Family : FamilyBase {
 public:
 	// Get a unique ID for a given type.
-	// Note: IDs will be unique across DLL-boundaries even for the same type.
+	// Note: An ID for a given type may not match across DLL-boundaries.
 	static FamilyId Id()
 	{
 		static int id = GetNewId();

Source/Core/CMakeLists.txt

@@ -195,6 +195,7 @@ add_library(rmlui_core
 	TextureLayoutRow.h
 	TextureLayoutTexture.cpp
 	TextureLayoutTexture.h
+	Traits.cpp
 	Transform.cpp
 	TransformPrimitive.cpp
 	TransformState.cpp

Source/Core/Traits.cpp

@@ -0,0 +1,38 @@
+/*
+ * This source file is part of RmlUi, the HTML/CSS Interface Middleware
+ *
+ * For the latest information, see http://github.com/mikke89/RmlUi
+ *
+ * Copyright (c) 2019-2024 The RmlUi Team, and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ */
+
+#include "../../Include/RmlUi/Core/Traits.h"
+
+namespace Rml {
+
+int FamilyBase::GetNewId()
+{
+	static int id = 0;
+	return id++;
+}
+
+} // namespace Rml