用OPC Client开发时，需要从如下几个地方注意内存泄露

用OPC Client开发时，需要从如下几个地方注意内存泄露：

（1）所有返回的指针，都要用CoTaskMemFree释放，如：

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function Group_TryAddItems(AGroupIntf:IOPCItemMgt;AItemCount:integer;AItems:POPCITEMDEFARRAY):POPCITEMRESULTARRAY;

var

vErrors: PResultList;

begin

Result:=nil;

vErrors:=nil;

if AGroupIntf.AddItems(AItemCount,PSafeArray(AItems),Result,vErrors)<>S_OK then

begin

CoTaskMemFree(Result);

Result:=nil;

end;

CoTaskMemFree(vErrors);

end;

（2）用ISyncRead接口读取资料后，要用VariantClear释放，如：

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function Group_ReadItem2(AGroupIntf:IOPCItemMgt;AItemServerHandle:OPCHandle;out AQuality:Word):OLEVariant;

var

vErrors:PResultList;

vOPCSyncIO:IOPCSyncIO;

ItemValues: POPCITEMSTATEARRAY;

begin

OLECheck(AGroupIntf.QueryInterface(IID_IOPCSyncIO,vOPCSyncIO));

try

OPCErrorCheck(vOPCSyncIO.Read(OPC_DS_DEVICE,1,@AItemServerHandle,ItemValues,vErrors));

try

OPCResultErrorsCheck(1,nil,null,vErrors);

Result:=ItemValues^[0].vDataValue;

AQuality:=ItemValues^[0].wQuality;

finally

VariantClear(ItemValues^[0].vDataValue); //memory leak

CoTaskMemFree(ItemValues);

end;

finally

vOPCSyncIO:=nil;

end;

end;