The attached files implement the CALL_EXTERNAL function for GDL on Unix/Linux Systems (with dlopen/dlsym).
The code itself is in the files new.cpp, new.hpp, and you have to define the routine in libinit.cpp (see the instructions in README.call_external).
The files test_ce.pro and test_ce.c can be used to test the routine.
Shared objects which are used with IDL can also be used with GDL, even strings and structures are passed the same way as in IDL to the called routine.
All IDL keywords are implemented except CDECL (relevant for MS Windows only), WRITE_WRAPPER and all AUTO_GLUE keywords (you have to write and compile your routines yourself :-)
See the attached File README.call_external for more information on Installation, Testing and Syntax.