如何避免OPC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：

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：

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;