# NeedsLatentFixup

- **功能描述：** 用在FLatentActionInfo::Linkage属性上，告诉蓝图VM生成跳转信息
- **使用位置：** UPROPERTY
- **元数据类型：** bool
- **关联项：** [Latent](Latent.md)
- **常用程度：** ★

## 在源码里找到的用处：

```cpp
USTRUCT(BlueprintInternalUseOnly)
struct FLatentActionInfo
{
	GENERATED_USTRUCT_BODY()

	/** The resume point within the function to execute */
	UPROPERTY(meta=(NeedsLatentFixup = true))
	int32 Linkage;

	//...
};

```

## 源码里发挥作用的地方：

看着就是把Linkage这个属性进行单独的处理。用来在JumpTargetFixupMap里进行专门的跳转

```cpp
void EmitLatentInfoTerm(FBPTerminal* Term, FProperty* LatentInfoProperty, FBlueprintCompiledStatement* TargetLabel)
{
	// Special case of the struct property emitter.  Needs to emit a linkage property for fixup
	FStructProperty* StructProperty = CastFieldChecked<FStructProperty>(LatentInfoProperty);
	check(StructProperty->Struct == LatentInfoStruct);

	int32 StructSize = LatentInfoStruct->GetStructureSize();
	uint8* StructData = (uint8*)FMemory_Alloca(StructSize);
	StructProperty->InitializeValue(StructData);

	// Assume that any errors on the import of the name string have been caught in the function call generation
	StructProperty->ImportText_Direct(*Term->Name, StructData, NULL, 0, GLog);

	Writer << EX_StructConst;
	Writer << LatentInfoStruct;
	Writer << StructSize;

	checkSlow(Schema);
	for (FProperty* Prop = LatentInfoStruct->PropertyLink; Prop; Prop = Prop->PropertyLinkNext)
	{
		if (TargetLabel && Prop->GetBoolMetaData(FBlueprintMetadata::MD_NeedsLatentFixup))
		{
			// Emit the literal and queue a fixup to correct it once the address is known
			Writer << EX_SkipOffsetConst;
			CodeSkipSizeType PatchUpNeededAtOffset = Writer.EmitPlaceholderSkip();
			JumpTargetFixupMap.Add(PatchUpNeededAtOffset, FCodeSkipInfo(FCodeSkipInfo::Fixup, TargetLabel));
		}
		else if (Prop->GetBoolMetaData(FBlueprintMetadata::MD_LatentCallbackTarget))
		{
			FBPTerminal CallbackTargetTerm;
			CallbackTargetTerm.bIsLiteral = true;
			CallbackTargetTerm.Type.PinSubCategory = UEdGraphSchema_K2::PN_Self;
			EmitTermExpr(&CallbackTargetTerm, Prop);
		}
		else
		{
			// Create a new term for each property, and serialize it out
			FBPTerminal NewTerm;
			if(Schema->ConvertPropertyToPinType(Prop, NewTerm.Type))
			{
				NewTerm.bIsLiteral = true;
				Prop->ExportText_InContainer(0, NewTerm.Name, StructData, StructData, NULL, PPF_None);

				EmitTermExpr(&NewTerm, Prop);
			}
			else
			{
				// Do nothing for unsupported/unhandled property types. This will leave the value unchanged from its constructed default.
				Writer << EX_Nothing;
			}
		}
	}

	Writer << EX_EndStructConst;
}
```