undefined reference to `TC_SYSTEM_ISLIBRARY'

[xnapoleonx]

Hello,

I'm new to Lazarus and I'm trying to test just the basics.

I installed Lazarus on Linux (Ubuntu).
(1)
Then I created a new project with a form, two button, two edits and one label, and I wrote just two functions:

Code: Pascal  [Select][+][-]

1. function myadd(a, b : integer): integer;
2. begin
3.   Result := a + b;
4. end;
5.  
6. function myminus(a, b : integer): integer;
7. begin
8.   Result := a - b;
9. end;

Really a very simple test, it works fine.

(2)
Then I created a new project " LIBRARY" and wrote just those two functions "myadd" and "myminus".
The project was successfully compiled and the library was created "libmymath.so".
I copied the library to /usr/lib folder and ran ldconfig. (OK)

(3)
Then I created a new project like the first one, with a form, button, etc.. and added the library "libmymath.so"
This was really very simple, and it works fine and without any problem.

Now and after all 3 tests were successful, I installed Lazarus on a Raspberry (Raspian) (Lazarus 1.2.4 & FPC 2.6.4).
I did the same as before:
I was able to create a simple project as (1). It works fine and without any problem.
I was able to create the library "libmymath.so" as (2). No problems.

But the 3. test:
I copied the library to /usr/lib folder and ran ldconfig: OK
I created a new project and added my library as in step (3) and tried to compile the project.
The project was not built and I got the following error:

//usr/lib/libmymath.so: undefined reference to `TC_SYSTEM_ISLIBRARY'

I have no idea what does "TC_SYSTEM_ISLIBRARY" mean, and I'm unable to find any information about it.

Does anybody know what does this error mean?

I would really appreciate your help.
Thank you.

[balazsszekely]

Did you linked the library statically? I would try a  dynamically loaded/unloaded approach, during execution

[xnapoleonx]

Thank you.

yes, I linked the library statically.
I'll try to dynamically load/unload it.

[balazsszekely]

@xnapoleonx
Thank you.
yes, I linked the library statically.
I'll try to dynamically load/unload it.

You're welcome, something like this(see attachment):

1. Library

Code: Pascal  [Select][+][-]

1. library libmymath;
2.  
3. {$mode objfpc}{$H+}
4.  
5.  
6. function MyAdd(a, b: Integer): Integer; cdecl;
7. begin
8.   Result := a + b;
9. end;
10.  
11. function MyMinus(a, b: Integer): Integer; cdecl;
12. begin
13.   Result := a - b;
14. end;
15.  
16. exports
17.   MyAdd,
18.   MyMinus;
19.  
20. begin
21. end.

1. Application

Code: Pascal  [Select][+][-]

1. //...
2. var
3.   LibHandle: TLibHandle = NilHandle;
4.  
5. procedure TfMain.FormCreate(Sender: TObject);
6. var
7.   LibName: String;
8. begin
9.  LibName := ExtractFilePath(ParamStr(0)) + 'libmymath.' + SharedSuffix;
10.  LibHandle := LoadLibrary(LibName);
11.  if LibHandle = NilHandle then
12.    ShowMessage('Cannot load library');
13. end;
14.  
15. procedure TfMain.FormDestroy(Sender: TObject);
16. begin
17.  if LibHandle <> NilHandle then
18.  begin
19.    UnloadLibrary(LibHandle);
20.    LibHandle := NilHandle;
21.  end;
22. end;
23.  
24. procedure TfMain.bTestPlusClick(Sender: TObject);
25. type
26.   TMyAdd = function(a, b: Integer): Integer; cdecl;
27. var
28.   FarProc: TFarProc;
29.   MyAdd: TMyAdd;
30. begin
31.   if LibHandle = NilHandle then
32.     Exit;
33.   FarProc := GetProcedureAddress(LibHandle, 'MyAdd');
34.   if FarProc <> nil then
35.   begin
36.     MyAdd := TMyAdd(FarProc);
37.     ShowMessage(IntToStr(MyAdd(7, 3)));
38.   end;
39. end;
40.  
41.  
42. procedure TfMain.bTestMinusClick(Sender: TObject);
43. type
44.   TMyMinus = function(a, b: Integer): Integer; cdecl;
45. var
46.   FarProc: TFarProc;
47.   MyMinus: TMyMinus;
48. begin
49.   if LibHandle = NilHandle then
50.     Exit;
51.   FarProc := GetProcedureAddress(LibHandle, 'MyMinus');
52.   if FarProc <> nil then
53.   begin
54.     MyMinus := TMyMinus(FarProc);
55.     ShowMessage(IntToStr(MyMinus(7, 3)));
56.   end;
57. end;

PS: It should work cross platform way. Works well under ubuntu, I don't have Raspberry to run a few test. Please test it!

[xnapoleonx]

unfortunately not, it does not work.

LoadLibrary returns NilHandle.
GetLoadErrorStr returns an empty string.

I tried it with:
(1) LibName = 'libmymath.so'
(2) LibName = <absolute path>'/libmymath.so'
(3) LibName = ExtractFilePath(ParamStr(0)) + 'libmymath.' + SharedSuffix (= (2))

[balazsszekely]

@xnapoleonx
Then must be some Raspberry specific stuff, because I just tested under windows(32/64), linux, osx. Works fine.

PS: Please do a quick google search, maybe there is some documented issue with the libraries under Raspberry.

[xnapoleonx]

Yes, I think so.

I think , the problem is not how to load/unload the library. I think it is the way how the library is created!
The error "//usr/lib/libmymath.so: undefined reference to `TC_SYSTEM_ISLIBRARY'" maybe means that this `TC_SYSTEM_ISLIBRARY' is within the library not defined.

While creating a library, is there any option/settings/etc. to tell the compiler, that this is a library? Or to define this unknown `TC_SYSTEM_ISLIBRARY'?

[balazsszekely]

While creating a library, is there any option/settings/etc. to tell the compiler, that this is a library? Or to define this unknown `TC_SYSTEM_ISLIBRARY'?

Not that I am aware of.

I found the, following links(just search for: TC_SYSTEM_ISLIBRARY):
     http://zengl.googlecode.com/svn/branches/0.3.x/src/zgl_application.pas
     https://fossies.org/diffs/fpcbuild/2.6.4_vs_3.0.0/fpcsrc/rtl/linux/arm/dllprt0.as-diff.html (what is you fpc version?)
Unfortunately is still a mistery what TC_SYSTEM_ISLIBRARY is. I searched the FPC/Lazarus folders, found nothing. Let's wait, maybe somebody has a better idea.

[xnapoleonx]

I just copied a library from "/usr/lib' to my project folder and tried to load it dynamically: YES IT WORKS.
So I think, it is really how the library is created!


FPC Version: 2.6.4

[balazsszekely]

So I think, it is really how the library is created!

Yes it's possible! Or perhaps some privilege issue?

[xnapoleonx]

Your library, as I downloaded it:

pi@raspberrypi:~ $ file /home/pi/Downloads/Library/libmymath.so
/home/pi/Downloads/Library/libmymath.so: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), dynamically linked, not stripped

pi@raspberrypi:~ $ nm -DC /home/pi/Downloads/Library/libmymath.so
00006200 T MyAdd
00006210 T MyMinus


I re-compiled it (on Raspberry)

pi@raspberrypi:~ $ file /home/pi/Downloads/Library/Library/libmymath.so
/home/pi/Downloads/Library/Library/libmymath.so: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, not stripped

pi@raspberrypi:~ $ nm -DC /home/pi/Downloads/Library/Library/libmymath.so
0000472c T MyAdd
00004730 T MyMinus
                 U TC_SYSTEM_ISLIBRARY

After I re-compiled it, the symbol "TC_SYSTEM_ISLIBRARY" was added!?

[balazsszekely]

Ok.. at least we know this ,  but I suppose the loading still not works?

PS: Can you please try to change the permission of that library?

[xnapoleonx]

I changed the permission using the command "chmod 777" to

-rwxrwxrwx 1 pi pi   390376 Feb 11 18:05 libmymath.so

and still not works!

[xnapoleonx]

It is a Lazarus/FPC bug. 
If the library was created with FPC (ARMHF) on Raspberry, then it is not possible to load the library with Lazarus/FPC.

I installed FPC 3.1.1 and Lazarus 1.7 on Raspberry => STILL DOES NOT WORK.
The TC_SYSTEM_ISLIBRARY error is not shown any more.
But GetLoadErrorStr returns ".....can not open file...file or folder not found.."

It is possible to load other libraries (not created with FPC) 

[balazsszekely]

@xnapoleonx
It is a Lazarus/FPC bug. 

Then please report it on the bugtracker: http://bugs.freepascal.org/main_page.php

It is possible to load other libraries (not created with FPC)

As a temporary solution, can you create the library in some other language?