Solon 1.6.6 发布,细节打磨
573 2023-04-03 03:41:15
Version:4.26.2
UE4 C++工程名:MyProject
在《宏GENERATED_BODY做了什么?》中,简单分析了GENERATED_BODY宏给一个简单的、继承自UObject的自定义类添加了什么。
当中涉及到的源码文件有:ObjectMacros.h、MyObject.h、MyObject.generated.h, UObjectGlobals.h;
现在来分析一下UHT生成的另外一个文件:MyObject.gen.cpp
当中会额外涉及到的源文件有:UObjectBase.h, UObjectBase.cpp, Class.h, Class.cpp, UObjectGlobals.cpp
先无脑贴一下代码,部分会添加中文注释
// Copyright Epic Games, Inc. All Rights Reserved./*===========================================================================Generated code exported from UnrealHeaderTool.DO NOT modify this manually! Edit the corresponding .h files instead!===========================================================================*/#include "UObject/GeneratedCppIncludes.h"#include "MyProject/Public/MyObject.h"#ifdef _MSC_VER#pragma warning (push)#pragma warning (disable : 4883)#endifPRAGMA_DISABLE_DEPRECATION_WARNINGSvoid EmptyLinkFunctionForGeneratedCodeMyObject() {}// Cross Module ReferencesMYPROJECT_API UClass* Z_Construct_UClass_UMyObject_NoRegister();MYPROJECT_API UClass* Z_Construct_UClass_UMyObject();COREUOBJECT_API UClass* Z_Construct_UClass_UObject();UPackage* Z_Construct_UPackage__Script_MyProject();// End Cross Module Referencesvoid UMyObject::StaticRegisterNativesUMyObject(){}UClass* Z_Construct_UClass_UMyObject_NoRegister(){return UMyObject::StaticClass();}struct Z_Construct_UClass_UMyObject_Statics{static UObject* (*const DependentSingletons[])();#if WITH_METADATAstatic const UE4CodeGen_Private::FMetaDataPairParam Class_MetaDataParams[];#endifstatic const FCppClassTypeInfoStatic StaticCppClassTypeInfo;static const UE4CodeGen_Private::FClassParams ClassParams;};UObject* (*const Z_Construct_UClass_UMyObject_Statics::DependentSingletons[])() = {(UObject* (*)())Z_Construct_UClass_UObject,(UObject* (*)())Z_Construct_UPackage__Script_MyProject,};#if WITH_METADATAconst UE4CodeGen_Private::FMetaDataPairParam Z_Construct_UClass_UMyObject_Statics::Class_MetaDataParams[] = {{ "BlueprintType", "true" },{ "Comment", "/**\n *n */" },{ "IncludePath", "MyObject.h" },{ "ModuleRelativePath", "Public/MyObject.h" },{ "ObjectInitializerConstructorDeclared", "" },};#endifconst FCppClassTypeInfoStatic Z_Construct_UClass_UMyObject_Statics::StaticCppClassTypeInfo = {TCppClassTypeTraits<UMyObject>::IsAbstract,};// UE_ARRAY_COUNT宏计算数组的大小// METADATA_PARAMS简单的宏拆成两个参数,或者支取第二个宏;根据WITH_METADATA宏是否有定义;参看UObjectGlobals.h源文件中的定义const UE4CodeGen_Private::FClassParams Z_Construct_UClass_UMyObject_Statics::ClassParams = {&UMyObject::StaticClass,nullptr,&StaticCppClassTypeInfo,DependentSingletons,nullptr,nullptr,nullptr,UE_ARRAY_COUNT(DependentSingletons), 0,0,0,0x001000A0u,METADATA_PARAMS(Z_Construct_UClass_UMyObject_Statics::Class_MetaDataParams, UE_ARRAY_COUNT(Z_Construct_UClass_UMyObject_Statics::Class_MetaDataParams)) };// 关注点-1UClass* Z_Construct_UClass_UMyObject(){static UClass* OuterClass = nullptr;if (!OuterClass){UE4CodeGen_Private::ConstructUClass(OuterClass, Z_Construct_UClass_UMyObject_Statics::ClassParams);}return OuterClass;}// IMPLEMENT_CLASS(UMyObject, 1944586990); // 下面时宏展开后的代码// 关注点-2static TClassCompiledInDefer<UMyObject> AutoInitializeUMyObject(TEXT("UMyObject"), sizeof(UMyObject), 1944586990);UClass* UMyObject::GetPrivateStaticClass(){static UClass* PrivateStaticClass = NULL;if (!PrivateStaticClass){/* this could be handled with templates, but we want it external to avoid code bloat */GetPrivateStaticClassBody(StaticPackage(),(TCHAR*)TEXT("UMyObject") + 1 + ((StaticClassFlags & CLASS_Deprecated) ? 11 : 0),PrivateStaticClass,StaticRegisterNativesUMyObject,sizeof(UMyObject),alignof(UMyObject),(EClassFlags)UMyObject::StaticClassFlags,UMyObject::StaticClassCastFlags(),UMyObject::StaticConfigName(),(UClass::ClassConstructorType)InternalConstructor<UMyObject>,(UClass::ClassVTableHelperCtorCallerType)InternalVTableHelperCtorCaller<UMyObject>,&UMyObject::AddReferencedObjects,&UMyObject::Super::StaticClass,&UMyObject::WithinClass::StaticClass);}return PrivateStaticClass;}template<> MYPROJECT_API UClass* StaticClass<UMyObject>(){return UMyObject::StaticClass();}// 关注点-3static FCompiledInDefer Z_CompiledInDefer_UClass_UMyObject(Z_Construct_UClass_UMyObject, &UMyObject::StaticClass, TEXT("/Script/MyProject"), TEXT("UMyObject"), false, nullptr, nullptr, nullptr);// DEFINE_VTABLE_PTR_HELPER_CTOR(UMyObject); // 下面时宏展开后的代码UMyObject::UMyObject(FVTableHelper& Helper) : Super(Helper) {};PRAGMA_ENABLE_DEPRECATION_WARNINGS#ifdef _MSC_VER#pragma warning (pop)#endif
上面代码中加了三个关注点注释,下面是一点分析
上面罗列了一下MyObject.gen.cpp文件的内容,下面来分析一下关注点
先看【关注点-3】吧,该类定义在UObjectBase.h文件中:
struct FCompiledInDefer{FCompiledInDefer(class UClass *(*InRegister)(), class UClass *(*InStaticClass)(), const TCHAR* PackageName, const TCHAR* Name, bool bDynamic, const TCHAR* DynamicPackageName = nullptr, const TCHAR* DynamicPathName = nullptr, void (*InInitSearchableValues)(TMap<FName, FName>&) = nullptr){if (bDynamic){GetConvertedDynamicPackageNameToTypeName().Add(FName(DynamicPackageName), FName(Name));}UObjectCompiledInDefer(InRegister, InStaticClass, Name, PackageName, bDynamic, DynamicPathName, InInitSearchableValues);}};
构造函数内部直接调用了UObjectCompiledInDefer(...)
函数;
由于参数bDynamic=false
,函数UObjectCompiledInDefer(...)
内部有效的代码如下:
TArray<UClass *(*)()>& DeferredCompiledInRegistration = GetDeferredCompiledInRegistration();checkSlow(!DeferredCompiledInRegistration.Contains(InRegister));DeferredCompiledInRegistration.Add(InRegister);
函数GetDeferredCompiledInRegistration()
定义如下:
static TArray<class UClass *(*)()>& GetDeferredCompiledInRegistration(){static TArray<class UClass *(*)()> DeferredCompiledInRegistration;return DeferredCompiledInRegistration;}
内部的数组DeferredCompiledInRegistration
也是静态对象;
参数InRegister
这个函数指针加入DeferredCompiledInRegistration
数组中;
即函数Z_Construct_UClass_UMyObject
地址会被加入到DeferredCompiledInRegistration
数组中;
【关注点-2】这个类同样定义在UObjectBase.h文件中;
与FCompiledInDefer写法类似
区别是这里将static TClassCompiledInDefer<UMyObject> AutoInitializeUMyObject
这个对象加入另了一个静态数组中;
这里不再赘述了;
【关注点-1】有啥好说的呢?
上面分析,这个函数通过函数指针被添加到静态数组DeferredCompiledInRegistration
;
这里需要关注:
ConstructUClass
函数调的第二个参数是Z_Construct_UClass_UMyObject_Statics::ClassParams
, 这正是上半部分代码对UMyObject类信息的收集数据ConstructUClass
这个函数定义在UObjectGlobals.h/UObjectGlobals.cpp文件中;
Z_Construct_UClass_UMyObject(...) -> ConstructUClass(...) -> UMyObject::StaticClass() -> UMyObject::GetPrivateStaticClass() -> GetPrivateStaticClassBody(...)
GetPrivateStaticClass()
中就可以看出,一个自定义类只会创建一个UClass对象;Z_Construct_UClass_UMyObject
只是做了注册,真正调用的时候是在引擎初始化阶段;上面罗列了一下MyObject.gen.cpp中有什么东西;
并且分下了一下关键的注册机制;
在MyObject.gen.cpp中,通过静态对象的特性(程序加载时就会被创建,并且时间早于main函数),收集自定义类的信息:
static TClassCompiledInDefer<UMyObject> AutoInitializeUMyObject
对象,收集名字、size、一个唯一ID;static FCompiledInDefer Z_CompiledInDefer_UClass_UMyObject
对象,注册一个函数,该函数返回一个UClass对象,该对象用来描述UMyObject类;需要重复指出的是,整个类型信息注册的时机是在程序加载阶段,要早于main函数;
但类型自动注册的总体机制是相同的。
完结