vault backup: 2024-10-12 17:19:45

2024-10-12 17:19:46 +08:00
parent ff94ddca61
commit 244c0c52f6
960 changed files with 31348 additions and 10 deletions
--- a/03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Specifier/USTRUCT/UHT/IsAlwaysAccessible.md
+++ b/03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Specifier/USTRUCT/UHT/IsAlwaysAccessible.md
@@ -0,0 +1,120 @@
+# IsAlwaysAccessible
+
+- **功能描述：** 指定UHT在生成文件的时候总是可以访问到改结构的声明，否则要在gen.cpp里生成镜像结构定义
+- **元数据类型：** bool
+- **引擎模块：** UHT
+- **限制类型：** 只在NoExportTypes.h供UHT使用
+- **常用程度：** 0
+
+指定该结构的声明是否在UHT为NoExportTypes.h生成的gen.cpp里总是可以访问到。
+
+换句话说其实就是是否这些结构在GeneratedCppIncludes.h的声明里可以找到。如果不可以找到，那在后面生成Z_Construct_UScriptStruct_FMatrix44d_Statics这种类似的时候就得再自己定义一个镜像结构定义。如果可以找到，比如FGuid，则就不需要。
+
+因此这只是一个手动的内部标记，帮助UHT程序识别哪些结构要再创建镜像结构定义。
+
+在NoExportTypes.h查看各个结构的时候，会发现有些结构（85/135）会标上IsAlwaysAccessible，而有些没有。这是因为UHT在为NoExportTypes.h生成gen.cpp的时候，
+
+```cpp
+\UnrealEngine\Engine\Source\Runtime\CoreUObject\Public\UObject\GeneratedCppIncludes.h
+#include "UObject/Object.h"
+#include "UObject/UObjectGlobals.h"
+#include "UObject/CoreNative.h"
+#include "UObject/Class.h"
+#include "UObject/MetaData.h"
+#include "UObject/UnrealType.h"
+#include "UObject/EnumProperty.h"
+#include "UObject/TextProperty.h"
+#include "UObject/FieldPathProperty.h"
+
+#if UE_ENABLE_INCLUDE_ORDER_DEPRECATED_IN_5_2
+#include "CoreMinimal.h"
+#endif
+
+\Hello\Intermediate\Build\Win64\HelloEditor\Inc\CoreUObject\UHT\NoExportTypes.gen.cpp：
+// Copyright Epic Games, Inc. All Rights Reserved.
+/*===========================================================================
+	Generated code exported from UnrealHeaderTool.
+	DO NOT modify this manually! Edit the corresponding .h files instead!
+===========================================================================*/
+
+//以下这两行
+#include "UObject/GeneratedCppIncludes.h"//A
+#include "UObject/NoExportTypes.h"//B
+PRAGMA_DISABLE_DEPRECATION_WARNINGS
+void EmptyLinkFunctionForGeneratedCodeNoExportTypes() {}
+```
+
+在最开头的两个include里如果可以直接找到该struct的定义，则在gen.cpp中的A和B处需要结构定义的时候，就不需要再额外去找定义了。
+
+```cpp
+const UECodeGen_Private::FStructParams Z_Construct_UScriptStruct_FMatrix44f_Statics::ReturnStructParams = {
+		(UObject* (*)())Z_Construct_UPackage__Script_CoreUObject,
+		nullptr,
+		nullptr,
+		"Matrix44f",
+		Z_Construct_UScriptStruct_FMatrix44f_Statics::PropPointers,
+		UE_ARRAY_COUNT(Z_Construct_UScriptStruct_FMatrix44f_Statics::PropPointers),
+		sizeof(FMatrix44f),//这个A
+		alignof(FMatrix44f),//这个B
+		RF_Public|RF_Transient|RF_MarkAsNative,
+		EStructFlags(0x00000038),
+		METADATA_PARAMS(UE_ARRAY_COUNT(Z_Construct_UScriptStruct_FMatrix44f_Statics::Struct_MetaDataParams), Z_Construct_UScriptStruct_FMatrix44f_Statics::Struct_MetaDataParams)
+	};
+```
+
+如果找不到，比如FMatrix44f，是定义在Engine\Source\Runtime\Core\Public\Math\Matrix.h，则必须为它生成一个一模一样的定义（不include的作用是加快编译)：
+
+```cpp
+struct Z_Construct_UScriptStruct_FMatrix44f_Statics
+	{
+		struct FMatrix44f //内存布局一致的定义
+		{
+			FPlane4f XPlane;
+			FPlane4f YPlane;
+			FPlane4f ZPlane;
+			FPlane4f WPlane;
+		};
+
+		static_assert(sizeof(FMatrix44f) < MAX_uint16);
+		static_assert(alignof(FMatrix44f) < MAX_uint8);
+```
+
+当然如果子字段或者父类也找不到定义，则只需要把父定义先写在前面就可以了。因此cs里的FindNoExportStructsRecursive就是为了找到其相关的结构。没有标IsAlwaysAccessible则意味着要生成假的结构定义
+
+```cpp
+private static void FindNoExportStructsRecursive(List<UhtScriptStruct> outScriptStructs, UhtStruct structObj)
+		{
+			for (UhtStruct? current = structObj; current != null; current = current.SuperStruct)
+			{
+				// Is isn't true for noexport structs
+				if (current is UhtScriptStruct scriptStruct)
+				{
+					if (scriptStruct.ScriptStructFlags.HasAnyFlags(EStructFlags.Native))
+					{
+						break;
+					}
+
+					// these are a special cases that already exists and if wrong if exported naively
+					if (!scriptStruct.IsAlwaysAccessible)
+					{
+						outScriptStructs.Remove(scriptStruct);
+						outScriptStructs.Add(scriptStruct);
+					}
+				}
+
+				foreach (UhtType type in current.Children)
+				{
+					if (type is UhtProperty property)
+					{
+						foreach (UhtType referenceType in property.EnumerateReferencedTypes())
+						{
+							if (referenceType is UhtScriptStruct propertyScriptStruct)
+							{
+								FindNoExportStructsRecursive(outScriptStructs, propertyScriptStruct);
+							}
+						}
+					}
+				}
+			}
+		}
+```