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How to Call DLL's function?

Posted on 2000-03-07
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Last Modified: 2010-08-05
Hello, I want to call DLL's function at Delphi 4, I have declared the function like this:
procedure openport(n:string);external 'c:\eztt95.dll'

the program can be complied, but while executed the follow statement -- openport('0'), it show a error message--'privilege structure', whatis it mean?

I have use same DLL at VB6, it is workable. the declare statemnet is
  Private Declare Sub openport lib "c:\eztt95.dll"(ByVal command$)

the execute statement is
  call openport("0")

have I made some mistake with extrenal function declaration?

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Question by:kelvinyu
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by:yk030299
ID: 2594256
listen
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Accepted Solution

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rwilson032697 earned 50 total points
ID: 2594262
The calling convention will be wrong, and the DL won't know about the short or huge pascal string types used by Delphi.

Try declaring OpenPort like this:

procedure openport(n:PChar); stdcall; external 'c:\eztt95.dll'

Cheers,

Raymond.
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Expert Comment

by:yk030299
ID: 2594288
strange. Why do I become KELVINYU?
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Expert Comment

by:yk030299
ID: 2594291
When I open this page, it show me that
this is my question and I am Kelvinyu
and I have 465pts only.
too strange!
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Author Comment

by:kelvinyu
ID: 2594326
is it?
this question is post by me(kelvinYu)

your link may have some problem
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Expert Comment

by:sunsetyang
ID: 2594687
delphi can only execute dll's function dynamically by load it and execute by load the right function or procedure.
you'd better write like this:
handle=LoadLibrary('xxx.dll');
pProc=GetProcAddress(handle,'FunctionName');
ProcType(pProc)(....);
FreeLibrary(handle);
Above handle is a THandle Type variable,
pProc is a TFarProc Type variable,
ProcType is a type of your calling procedure.

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by:rwilson032697
ID: 2594876
sunsetyang: This is not true. kelvinyu is using early binding rather than late binding so he does not need to use LoadLibrary or GetProcAddress.

Cheers,

Raymond.
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Expert Comment

by:sunsetyang
ID: 2598751
sunsetyang changed the proposed answer to a comment
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Expert Comment

by:sunsetyang
ID: 2598757
Yeah,I am wrong for the question.
Rwilson,Thank you!
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Expert Comment

by:rwilson032697
ID: 2598767
sunsetyang: Does the change to the declaration work for you?

Cheers,

Raymond.
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Author Comment

by:kelvinyu
ID: 2610535
Rwilson,

I can call the Dll now,
thank you and thanks all

kelvin
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