Shered library in Ada - undefined symbols problem (Ubuntu)

Shered library in Ada - undefined symbols problem (Ubuntu)

[Maciej Sobczak]

Hi,

While trying to run the older program that was based on shared library written in Ada I have found that my library has some undefined symbols, namely:

interfaces__c_E

This symbol is defined in the libgnat.a library, but it is not linked in to my own shared library file. When the shared library is loaded with dlopen, the error message points to the above symbol as missing.

I have tried to force static linking of my shared library (to bring all dependent symbols into a single file), but the linker refused complaining about relocation issues - apparently the static version of the GNAT runtime library is not itself compiled with fPIC.

Any tips on how to move forward?

This is Linux Ubuntu, GNAT 4.6 from official packages.

-- 
Maciej Sobczak * http://www.msobczak.com * http://www.inspirel.com

Re: Shered library in Ada - undefined symbols problem (Ubuntu)

[Maciej Sobczak]

> This is Linux Ubuntu, GNAT 4.6 from official packages.

Interesting additional info: it works like a charm with GNAT GPL 2013 on the same system.

Does it qualify as a bug in the FSF version of GNAT?

Just in case you would like to reproduce it, the minimal test is described here:

http://www.inspirel.com/articles/Ada_Python_Binding.html

The code snippets are complete - it is enough to save them as files with appropriate names. The Python's ctypes.CDLL(...) presented in the example Python session is the critical line.

-- 
Maciej Sobczak * http://www.msobczak.com * http://www.inspirel.com

Re: Shered library in Ada - undefined symbols problem (Ubuntu)

[Simon Wright]

Maciej Sobczak <see.my.homepage@gmail.com> writes:

>> This is Linux Ubuntu, GNAT 4.6 from official packages.
>
> Interesting additional info: it works like a charm with GNAT GPL 2013
> on the same system.
>
> Does it qualify as a bug in the FSF version of GNAT?

No problem with FSF GCC 4.6.0 on Mac OS X.

I tried

   for Library_Auto_Init use "true";

and removing the calls to ada_moduleinit() and ada_modulefinal(), which
gave a segv on 4.6 but was fine on 4.8.1.

In both cases I used gprbuild, because of gnatmake's inability to deal
with .dylibs & rpath properly.

Re: Shered library in Ada - undefined symbols problem (Ubuntu)

[Maciej Sobczak]

> No problem with FSF GCC 4.6.0 on Mac OS X.

Thank you for checking.

> I tried
> 
>    for Library_Auto_Init use "true";
> 
> and removing the calls to ada_moduleinit() and ada_modulefinal(), which
> gave a segv on 4.6 but was fine on 4.8.1.

Which is a huge pity, as this difference will impact the portability of projects (the program will crash on one version or the other). Moreover, now I'm not even sure what is the intended/recommended strategy with regard to these calls.

> In both cases I used gprbuild, because of gnatmake's inability to deal
> with .dylibs & rpath properly.

Which brings the question: why not fix gnatmake in the first place?

-- 
Maciej Sobczak * http://www.msobczak.com * http://www.inspirel.com