Application doesn't seem to work when linked to library
lazarus / 32-Linux

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Michael Collier · 2012-01-21 15:30

Hi, When I link to an external library "dll.so" my calling application
doesn't appear to do anything (no forms appear or anything, but no
error messages either).

I have used libraries with success in Windows & Mac, and even tried a
really simple test (below):

I must have missed something??


The DLL ( copied to usr/local/lib )

library DLL;
{$mode objfpc}{$H+}
uses
   cmem
   {$IFDEF UNIX}{$IFDEF UseCThreads}
   ,cthreads
   {$ENDIF}{$ENDIF}
  ,Interfaces ,Forms ;
{$R *.res}
procedure test(); cdecl ;
begin
end ;
exports
 test ;
begin
  Application.Initialize;
end.

The Calling Program (simply declares the external procedure and
creates a form, but the form never appears, if I remove the external
declaration then it runs OK)

program call;
{$mode objfpc}{$H+}
uses
  cmem ,
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Interfaces,   Forms;

const dll = 'libdll' ;
procedure test() ; cdecl; external dll ;
{$R *.res}
var form : TForm ;
begin
  RequireDerivedFormResource := True;
  Application.Initialize;
  form := TForm.Create(Application);
  form.Show;
  Application.Run;
end.

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Michael Collier · 2012-01-21 15:39

My Bad I think..

I just copied the dll.so file to usr/lib rather than usr/local/lib and
it fires up now..

Does lazarus look in usr/local/lib during the compilation stage
though, because it didn't give any link errors when I pasted the dll
file there?

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Leledumbo · 2012-01-22 14:12

QuoteDoes lazarus look in usr/local/lib during the compilation stage
though, because it didn't give any link errors when I pasted the dll
file there?It looks for libraries in the (static) linker search path,
regardless the location is searched by the (dynamic) linker or not.

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Troodon · 2012-01-22 14:18

Try issuing ldconfig or rebooting your computer after you added a new
.so to one of the library folders.

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Michael Collier · 2012-01-22 15:16

Ok thanks guys, I didn't know about ldconfig, have added note to wiki
page