C Extensions: calling across extensions

[Gustavo Cordova]

> 
> I have two C Extension modules written for python.  Within 
> one module I want to create an instance of an object within
> another module.  Say the modules are named A and B.  Within
> A I have a creation method that looks something like:
> 
> PyObject* A_new (int param)
> {
>   AType* self = PyObject_New (AType, &AType_definition);
>   self->param = param;
>   return (PyObject*)self;
> }
> 
> within B i try to create an instance of AType like:
> 
> PyObject* A_new (int param);
> PyObject* somefunction (PyObject* self, PyObject* args)
> {
>   PyObject* p = A_new (5);
>   return p;
> }
> 
> both of these functions are in seperate modules in seperate .so files
> (linux).  I can import module A and everything works perfectly.  when i
> import module B i get the error:
> Import Error: ./B.so: undefined symbol: A_new
> 
> i compile both with
> gcc -shared -o A.so A.c
> gcc -shared -o B.so B.c
> 
> do i need to do special declarations for importing and exporting
> functions across shared objects for python extension modules? 
>  do i need
> to compile with a -l option?  any help would be appreciated.
> 
> thanks, Maxwell Sayles
> 

You need to link B.c against A.so, so that it'll know
from where to import any needed symbols:

gcc -shared -o B.so B.c A.so

(I think)

Also, use the -fPIC flag, to create relocatable code.

Good luck :-)

-gus