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Export Rec/Var from DLL

Posted on 1998-03-24
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Last Modified: 2010-04-06
I need data from a DLL (a Record and some Variables) in 4 units. I know how to export procedure and functions, but i can't access the record and the variables from these units.
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Question by:omsec
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Accepted Solution

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d003303 earned 30 total points
ID: 1360811
Yo,
all variables in a DLL are private to the DLL itself. To pass these variables between different modules (DLL/EXE, DLL/DLL) you need to use a procedural interface.

Slash/d003303
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Author Comment

by:omsec
ID: 1360812
do u mean, i shall write a procedure that do assigns the variables with data (initialize) and then export the whole thing to the host-program ?
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Expert Comment

by:d003303
ID: 1360813
Something like that :
library xyz

// stuff...

var MyVar : TMyStruct;

function GetMyVar: TMyStruct;
begin
  Result := MyVar;
end;

procedure SetMyVar(NewVar : TMyStruct);
begin
  MyVar := NewVar;
end;

// export these two

// or another way would be

var MyVar : TMyStruct
    MySecondVar : TAnotherStruct;

procedure GetMyVars(var FirstVar : TMyStruct; var SecondVar : TAnotherStruct);
begin
  FirstVar := MyVar;
  SecondVar := MySecondVar;
end;

procedure SetMyVars(FirstVar : TMyStruct; SecondVar : TAnotherStruct);
begin
  MyVar := FirstVar
  MySecondVar := SecondVar;
end;

// and export these two.

Slash/d003303
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Expert Comment

by:d003303
ID: 1360814
To clarify, I assumed these functions are called fromout the host application.
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Author Comment

by:omsec
ID: 1360815
yeah, i see what you mean there. but something makes that a lil difficultm, cos i have to export a record, well this isnt really the probrlem, but four of its fields are arrays. do ya want me do email you the dll-project ?
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Expert Comment

by:d003303
ID: 1360816
If you declare the record you are passing in your DLL and EXE, it should not be a problem. Many Win32API-structures are nested structures, and the API calls are all DLL interfaced.
E.g. create a unit that only declares the types you are using in your DLL and EXE in its interface section, and place it in your DLLs and EXEs uses clause.

Slash/d003303
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