DLL Problem

[captian jaster]

This is the program:

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. Uses
6.   Classes,SysUtils;
7.  
8. Procedure PrintHello;External 'Lib.dll'name'PrintHello';
9.  
10.  
11. begin
12.   PrintHello;
13.   Readln;
14. end.
15.  

This is the DLL:

Code: Pascal  [Select][+][-]

1. library Lib;
2.  
3.  
4. Procedure PrintHello;
5. begin
6.   Writeln('Hello World');
7. end;
8.  
9. {$IFDEF WINDOWS}{$R Lib.rc}{$ENDIF}
10.  
11. begin
12. end.
13.  
14. Export
15.   PrintHello;
16.  

It says "Failed to initialize program" (etc etc)

[Martin_fr]

Is that windows?
One possibility (there could be many more) would be the AntiVirus...

Happened to me once (same or similar error), BitDefender simply deletes some dll created by fpc.
Despite BitDefenders config being set to ask me, it deletes the file, with no warning.
There support team also never replied...

[captian jaster]

Is that windows?
One possibility (there could be many more) would be the AntiVirus...

Happened to me once (same or similar error), BitDefender simply deletes some dll created by fpc.
Despite BitDefenders config being set to ask me, it deletes the file, with no warning.
There support team also never replied...

Yeah its windows..
And I'm running MSE :\

[captian jaster]

I tried this code instead:

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. {$mode Delphi}{$H+}
4.  
5. Uses
6.   Classes,SysUtils,DynLibs;
7.  
8. Var
9.  PrintHello:Procedure;
10.  Handle:TLibHandle;
11.  
12.  
13. begin
14.   Handle := LoadLibrary('Lib.dll');
15.   if Handle = NilHandle then Writeln('Failed to Load library..')Else begin
16.     Writeln('Loaded Library! Assigning Procedures');
17.     @PrintHello := GetProcAddress(Handle,'PrintHello');
18.     Writeln('Got Procedure... Testing Procedure...');
19.     Sleep(1000);
20.     PrintHello;
21.     Readln;
22.   end;
23. end.
24.                        
25.  

It raises an External SigSegV Error and then when the Debug report comes up its a bunch of ??????

[Bart]

Maybe something like this?
(Untested code)

Code: [Select]

type
  THelloProc = Procedure;
var
  P: Pointer;
  PrintHello: THelloProc;

begin 
  Handle := LoadLibrary('Lib.dll'); 
  if Handle = NilHandle then Writeln('Failed to Load library..')
  Else
  begin 
    Writeln('Loaded Library! Assigning Procedures'); 
    P := GetProcAddress(Handle,'PrintHello'); 
    if (P <> nil) then  //you must check this!
    begin
      Writeln('Got Procedure... Testing Procedure...'); 
      PrintHello := THelloProc(P);
      Sleep(1000); 
      PrintHello; 
      Readln; 
    end
    else writeln('Unable to retriev adress of PrintHello from Lib.dll');
  end;
end;

Bart

[Laksen]

Here you go. Your original code is wrong. The compiler will ignore everything after your program text is over(the last "end."). And export is different from exports. Export is a procedure modifier that doesn't have a whole lot to do with exports in this context

Code: Pascal  [Select][+][-]

1. library TestLib;
2.  
3. Procedure PrintHello;
4. begin
5.    Writeln('Hello World');
6. end;
7.  
8. Exports
9.    PrintHello name 'PrintHello';
10.  
11. begin
12. end.
13.  

[captian jaster]

Here you go. Your original code is wrong. The compiler will ignore everything after your program text is over(the last "end."). And export is different from exports. Export is a procedure modifier that doesn't have a whole lot to do with exports in this context

Code: Pascal  [Select][+][-]

1. library TestLib;
2.  
3. Procedure PrintHello;
4. begin
5.    Writeln('Hello World');
6. end;
7.  
8. Exports
9.    PrintHello name 'PrintHello';
10.  
11. begin
12. end.
13.  

This worked.. Thanks..

Maybe something like this?
(Untested code)

Code: [Select]

type
  THelloProc = Procedure;
var
  P: Pointer;
  PrintHello: THelloProc;

begin 
  Handle := LoadLibrary('Lib.dll'); 
  if Handle = NilHandle then Writeln('Failed to Load library..')
  Else
  begin 
    Writeln('Loaded Library! Assigning Procedures'); 
    P := GetProcAddress(Handle,'PrintHello'); 
    if (P <> nil) then  //you must check this!
    begin
      Writeln('Got Procedure... Testing Procedure...'); 
      PrintHello := THelloProc(P);
      Sleep(1000); 
      PrintHello; 
      Readln; 
    end
    else writeln('Unable to retriev adress of PrintHello from Lib.dll');
  end;
end;

Bart

This code(Something like it) worked:

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. {$mode Delphi}{$H+}
4.  
5. Uses
6.   Classes,SysUtils,DynLibs;
7.  
8. Var
9.  PrintHello:TProcedure;
10.  Handle:TLibHandle;
11.  P:Pointer;
12.  
13. begin
14.   Handle := LoadLibrary('Lib.dll');
15.   if Handle = NilHandle then Writeln('Failed to load library!')Else begin
16.     Writeln('Got Library... Getting procedure');
17.     P := GetProcAddress(Handle,'PrintHello');
18.     if P <> Nil then
19.     begin
20.       Writeln('Got pointer.. Assigning...');
21.       PrintHello := TProcedure(P);
22.       Sleep(800);
23.       PrintHello;
24.     end Else Writeln('Failed to get procedure');
25.   end;
26.   Readln;
27. end.  
28.  

Thanks you guys

[cdbc]

Hi

P := GetProcAddress(Handle,'PrintHello'); 
if P <> Nil then PrintHello := TProcedure(P);
 
shorthand:

pointer(PrintHello):= GetProcAddress(Handle,'PrintHello');

Regards Benny

[Bart]

B.t.w. Probably the PrintHello should be declared as stdcall in my previous example.

Code: [Select]

type
  THelloProc = Procedure; stdcall;
var
  P: Pointer;
  PrintHello: THelloProc;

Bart

[cdbc]

Hi

@Bart

And then again, maybe not. Iirc the default calling convention in delphi and fpc is "register", which means "stdcall" will mangle the parameters and result...

"register" is supposed to be the fastest way...?!?

Code: [Select]

library Lib; 
 
 
Procedure PrintHello; { NO stdcall defined here, ie. register }
begin 
  Writeln('Hello World'); 
end; 
 
{$IFDEF WINDOWS}{$R Lib.rc}{$ENDIF} 
 
begin 
end. 
 
Exports
  PrintHello;


Regards Benny

[Bart]

You might be rigth.
I simply don't know, nor did I test 

Bart

[cdbc]

Hi.
@Cj
If you are interested, i could mail you a complete project with libraries and host application. Might inspire you, with some techniques...
Regards - Benny