dll파일의 내용
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<dllproject에서>
uses  unit1 in 'unit1.pas';

           exports   fmexecute3 index 1;

<unit1에서>
  interface
     function fmexecute3(s:string):string;stdcall

  implementation

functin fmexecute3(str1:string;str2:string):string;
begin
   result:=str1 + str2;  
end;  
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dll사용하기
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<dlluse.unit>

interface
   function(str1:string;str2:string):string;stdcall;
implementation
  function fmexecute3;stdcall;external 'MyData.DLL'

폼에 버튼을 만들구 텍스트를 넘져주면.
    buttonclick(~~~)
      var
               s1:string;
               s2:string;
            
      begin
                s1:=edit1.text;
                s2:=edit2.text;
               edit3.text:=fmexecute3(s1,s2);
   실행을 하면 에러가 나요. 'Invalid pointer operation' 왜 이런 에러가 날까요?