Embedding Example

[Ted Drain]

If you're building w/ gcc, add the link line option:

-Wl,-E

This says to pass the -E option to the linker.  This option tells the
linker to make all statically linked symbols available to the dynamic
libraries.  Without it, the symbols linked from libpython1.5.a aren't seen
by symbols in the dynamic libraries.

This really needs to be in the FAQ on embedding.

Ted

In article <397C6D55.6F7C at iems.nwu.edu>, "Leonardo B. Lopes"
<leo at iems.nwu.edu> wrote:

>I am trying to learn how to embed Python code in a C++ program. I got
>the example from the docs (the one that imports sys and prints out a
>couple of strings -- search from initxyzzy in google). The problem I get
>is that if I try to import any non-built in module, I get dynamic
>linking errors. For example, adding the following line 31 works:
>
>_______________________________________________________________________
>...
>     29         /* Execute some Python statements (in module __main__)
>*/
>     30         PyRun_SimpleString("import sys\n");
>-->  31         PyRun_SimpleString("import thread\n");
>     32         PyRun_SimpleString("print sys.builtin_module_names\n");
>...
>_______________________________________________________________________
>
>but adding the following line instead:
>
>_______________________________________________________________________
>...
>     29         /* Execute some Python statements (in module __main__)
>*/
>     30         PyRun_SimpleString("import sys\n");
>-->  31         PyRun_SimpleString("import random\n");
>     32         PyRun_SimpleString("print sys.builtin_module_names\n");
>...
>_______________________________________________________________________
>
>produces:
>
>_______________________________________________________________________
>[lopes at groucho lopes]$ ./demo 
>Hello, brave new world
>
>Traceback (innermost last):
>  File "<string>", line 1, in ?
>  File "/usr/lib/python1.5/random.py", line 22, in ?
>    import whrandom
>  File "/usr/lib/python1.5/whrandom.py", line 140, in ?
>    _inst = whrandom()
>  File "/usr/lib/python1.5/whrandom.py", line 46, in __init__
>    self.seed(x, y, z)
>  File "/usr/lib/python1.5/whrandom.py", line 58, in seed
>    import time
>ImportError: /usr/lib/python1.5/lib-dynload/timemodule.so: undefined
>symbol: PyExc_IOError
>('__builtin__', '__main__', 'imp', 'marshal', 'pcre', 'posix', 'regex',
>'signal', 'sys', 'thread')
>['xyzzy', 'os.path', 'os', 'exceptions', '__main__', 'posix',
>'whrandom', 'sys', '__builtin__', 'site', 'random', 'signal',
>'UserDict', 'posixpath', 'stat']
>./demo
>['./demo']
>_______________________________________________________________________
>
>I can imagine that for some reason there is some directory configuration
>missing to the interpreter when I start it embedded. How would I pass it
>this info?
>
>Thanks!
>Leo.
>
>
>

-- 
Ted Drain   Jet Propulsion Laboratory    Ted.Drain at jpl.nasa.gov