[fpc-devel] Problems linking FPC-built library into C program on linux x86_64

[Michael Van Canneyt]

On Wed, 24 May 2006, Dominique Leducq wrote:

> Hi again,
> 
> I still don't succeed in linking Free Pascal compiled code with a C program.
> 
> When linking with the shared library built by fpc, I have problems with undefined symbols, which are defined in the loaders. 
> 
> $ gcc -o test_shared test2.o -L. -lsoTest3
> ./libsoTest3.so: undefined reference to `__stkptr'
> ./libsoTest3.so: undefined reference to `_haltproc'
> ./libsoTest3.so: undefined reference to `operatingsystem_parameter_argc'
> ./libsoTest3.so: undefined reference to `operatingsystem_parameter_argv'
> collect2: ld returned 1 exit status
> 
> When linking in the loader prt0.o too, there are symbol conflicts with /usr/lib/crt1.o (_start, __data_start) if I call ld through gcc.
> 
> $ gcc -o test_shared test2.o prt0.o -L. -lsoTest3
> prt0.o: In function `_start':
> (.text+0x0): multiple definition of `_start'
> /usr/lib/gcc/x86_64-linux-gnu/4.0.3/../../../../lib64/crt1.o:../sysdeps/x86_64/elf/start.S:65: first defined here
> prt0.o: In function `data_start':
> (.data+0x0): multiple definition of `__data_start'
> /usr/lib/gcc/x86_64-linux-gnu/4.0.3/../../../../lib64/crt1.o:(.data+0x0): first defined here
> collect2: ld returned 1 exit status
> 
> 
> Exactly the same happens when linking statically.
> 
> 
>  If I call ld directly, linking succeeds, but the main() of the C program never gets called...
> 
> However, according to the FPC Programmer's Guide, "using a pascal library from a C program" (12.4) seems to be supported...
> 
> Do I miss something ?

That statement means that you can create a separate library, 
which can be called from a C program.

Doing what you want is to include pascal object files directly in a C program.
That is only possible if you create your own loader stub.

Michael.