[SOLVED] Can't access .so library function from Ubuntu
lazarus / 32-Linux

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Mujie · 2017-07-30 11:35

Hi,

In MS Windows I was successfully call the function from my own dll
library. Then I tried to crosscompile the sources  to Linux
(Elementary OS which is Ubuntu based). But no luck when result has
become standalone application on Ubuntu/Elementary OS.

Here is my OS
QuoteLinux G230 4.10.0-27-generic #30~16.04.2-Ubuntu SMP Thu Jun 29
16:07:46 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
My Lazarus IDE
QuoteLazarus 1.6.4 rUnversioned directory FPC 3.0.2 x86_64-linux-gtk 2
My application sources

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
//appcool.lprprogram appcool; {$mode objfpc}{$H+}//for threads{$define
UseCThreads} uses  {$IFDEF UNIX}{$IFDEF UseCThreads}  cthreads, 
{$ENDIF}{$ENDIF}  Interfaces, // this includes the LCL widgetset 
Forms, login_f, login_u  { you can add units after this }; {$R
*.res} begin  Application.Title:='Cool Application'; 
RequireDerivedFormResource:=True;  Application.Initialize; 
Application.CreateForm(TformLogin, formLogin);  Application.Run;end. 
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
//login_u.pas for unitunit login_u; {$mode
objfpc}{$H+} interface uses  Classes, SysUtils,  //additional 
LCLIntf, Dynlibs, Dialogs, Buttons; type //API Testing 
ThreadAPITesting = class(TThread)  protected    procedure LoadingLib; 
  procedure Execute; override;  end; procedure
ShowApiTesting; implementation //uses type //API TESTING//===========
API TESTING =============  TApiTesting = function (client_key,
client_secret: string): string; cdecl; //API TESTING procedure
ThreadApiTesting.LoadingLib;var  MyHandle: TLibHandle; 
ApiTestingFunc: TApiTesting;  DataResult: string;  client_key,
client_secret: string;begin  MyHandle :=
LoadLibrary('libs/libdbq.so');  if MyHandle<>0 then    begin     
ApiTestingFunc :=
TApiTesting(GetProcedureAddress(MyHandle,'ApiTesting'));      if
Assigned(@ApiTestingFunc) then        begin          DataResult :=
ApiTestingFunc('what', 'ever');        end;    FreeLibrary(MyHandle); 
  end  else    begin      FreeLibrary(MyHandle);     
ShowMessage('Library failed.');    end;  Exit;end; procedure
ThreadApiTesting.Execute;begin  if not Terminated then    begin     
Synchronize(@LoadingLib);      Exit;    end;end; procedure
ShowApiTesting;var ExecApiTesting:
ThreadApiTesting;begin ExecApiTesting :=
ThreadApiTesting.Create(False); ExecApiTesting.FreeOnTerminate :=
True; Exit;end; end.
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i //login_f
for formunit login_f; {$mode objfpc}{$H+} interface uses  Classes,
SysUtils, FileUtil, BCButton, Forms, Controls, Graphics,  Dialogs,
ExtCtrls, StdCtrls; type   { TformLogin }   TformLogin = class(TForm) 
  btLogin: TBCButton;    procedure btLoginClick(Sender: TObject);   
procedure FormCreate(Sender: TObject);  private    { private
declarations }  public    { public declarations }  end; var 
formLogin: TformLogin; implementation {$R *.lfm} uses  //Unit 
login_u; { TformLogin } procedure TformLogin.btLoginClick(Sender:
TObject);begin  ShowApiTesting();end; //anti flickerprocedure
TformLogin.FormCreate(Sender: TObject);begin 
Self.DoubleBuffered:=True;end; end. 
And the .so (dll) library

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
login; {$mode objfpc}{$H+} interface uses  Classes, SysUtils, 
//additional  LCLIntf, cmem; implementation function
ApiTesting(client_key, client_secret: string): string; cdecl;begin 
MessageBox(0,PChar('Success!'),PChar('Info'));end; exports
ApiTesting; 
Is there something I missed?

Thank you before.

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Thaddy · 2017-07-30 11:39

A dll is a library, not a program. Where's your main LIBRARY
code?.......
If it compiles to a dll it will compile to an .so on nixes. But your
code is no good anyway, so why bother?

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Mujie · 2017-07-30 11:46

Quote from: Thaddy on July 30, 2017, 01:39:33 pmA dll is a library,
not a program. Where's your main LIBRARY code?.......
If it compiles to a dll it will compile to an .so on nixes. But your
code is no good anyway, so why bother?

Hi,

Thanks for your reply. There is my main library codes, not good
enough 

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
login; {$mode objfpc}{$H+} interface uses  Classes, SysUtils, 
//additional  LCLIntf, cmem; implementation function
ApiTesting(client_key, client_secret: string): string; cdecl;begin 
MessageBox(0,PChar('Success!'),PChar('Info'));end; exports ApiTesting;

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molly · 2017-07-30 14:19

Quote from: Mujie on July 30, 2017, 01:46:11 pmThanks for your reply.
There is my main library codes, not good enough 
You are not creating a (shared) library there but, you are exporting
functions. There is an important difference there.

Programming shared libraries

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Mujie · 2017-07-30 16:27

Quote from: molly on July 30, 2017, 04:19:02 pmYou are not creating a
(shared) library there but, you are exporting functions. There is an
important difference there.

Programming shared libraries

Hi,

Thanks for your reply.

I got this messages from GetLoadErrorStr

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
libs/libdbq.so: undefined symbol: ApiTesting

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molly · 2017-07-30 16:56

Quote from: Mujie on July 30, 2017, 06:27:55 pmCode: Pascal
 [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
libs/libdbq.so: undefined symbol: ApiTestingYou have not showed us a
library unit named (lib)dbq so how would you expect it to load/link a
function named ApiTesting ?

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Thaddy · 2017-07-30 18:21

A library looks like this:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i library
somelibrary;interface  // not requiredexports... implementation // not
requiredend.It is not a program..... As you wrote, it's your own
library.... (some people lack their glasses)

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Leledumbo · 2017-07-31 04:44

You should try a simple program-library first. If you can make this
work on Linux, then you should have no problem doing it for more
complex program:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i library
mylib; uses  strings; // NEVER declare string as parameter in library
function, string is a managed type and each program and library has
their own copy of the memory managerfunction f(p: pchar): integer;
cdecl;begin  f := strlen(p);end; exports  f; end. Code: Pascal
 [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
mylibtest; uses  dynlibs; type Tf = function (p: pchar): integer; var 
OK: Boolean;  h: TLibHandle;  f: Tf;begin  OK := false;  h :=
 LoadLibrary('./libmylib.' + SharedSuffix);  if h <> NilHandle then
begin    f := Tf(GetProcedureAddress(h,'f'));    if Assigned(f) then
begin      WriteLn(f('test'));      OK := true;    end;  end;   if not
OK then    WriteLn(StdErr,GetLoadErrorStr);end.

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Thaddy · 2017-07-31 07:02

"// NEVER declare string as parameter in library function, string is a
managed type and each program and library has their own copy of the
memory manager"

Well. As long it is pure pascal for pure pascal, one could use {$H-}.
Shortstrings are not a managed string type!!

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Mujie · 2017-07-31 14:35

Hi LeleDumbo,

Thanks for your reply. Its look like I struggle with 'LCLIntf' on my
.so library source codes. I try to replace 'Windows' uses with
'LCLIntf'. My codes is fine on MS Windows, maybe I should take a look
another distro.


Quote from: Leledumbo on July 31, 2017, 06:44:37 amYou should try a
simple program-library first. If you can make this work on Linux, then
you should have no problem doing it for more complex program:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i library
mylib; uses  strings; // NEVER declare string as parameter in library
function, string is a managed type and each program and library has
their own copy of the memory managerfunction f(p: pchar): integer;
cdecl;begin  f := strlen(p);end; exports  f; end. Code: Pascal
 [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
mylibtest; uses  dynlibs; type Tf = function (p: pchar): integer; var 
OK: Boolean;  h: TLibHandle;  f: Tf;begin  OK := false;  h :=
 LoadLibrary('./libmylib.' + SharedSuffix);  if h <> NilHandle then
begin    f := Tf(GetProcedureAddress(h,'f'));    if Assigned(f) then
begin      WriteLn(f('test'));      OK := true;    end;  end;   if not
OK then    WriteLn(StdErr,GetLoadErrorStr);end.

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Mujie · 2017-07-31 14:38

Hi,

'library' syntax has been declare on .lpr
You're right about the glasses 

Quote from: Thaddy on July 30, 2017, 08:21:31 pmA library looks like
this:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i library
somelibrary;interface  // not requiredexports... implementation // not
requiredend.It is not a program..... As you wrote, it's your own
library.... (some people lack their glasses)

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Mujie · 2017-08-06 05:40

Hi,

It's me again, I solved this by adding the code into one instead of
the unit outside the library code.

Example

Work library codes
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
//myapilibrary.lpr library myapilibrary; {$mode objfpc}{$H+} uses 
Classes  { you can add units after this }; function ApiTesting(p:
PChar): integer; {$IFDEF MSWINDOWS}stdcall{$ELSE}cdecl{$ENDIF};begin 
ApiTesting:= strlen(p);end; exports ApiTesting; beginend.  

Not work on Ubuntu 16 and Centos 7, error message appears 'undefined
symbol ApiTesting'. But work on MS Windows 7 and MS Windows 10. I put
a function on unit and linked with lpr.
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
//myapilibrary.lpr library myapilibrary; {$mode objfpc}{$H+} uses 
Classes, myanotherunit  { you can add units after this }; beginend.  

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
//myanotherunit.pas unit myanotherunit; {$mode
objfpc}{$H+} interface uses  Classes,
SysUtils; implementation function ApiTesting(p: PChar): integer;
{$IFDEF MSWINDOWS}stdcall{$ELSE}cdecl{$ENDIF};begin  ApiTesting:=
strlen(p);end; exports ApiTesting; end.