Hello,
I'm trying to wrap a C++ library which uses dlopen to load a dynamic
library and I don't manage to get rid of an "undefined symbol" error.
I tried to simulate my problem with a simpler example so hopefully
someone may be able to tell me what I'm doing wrong.
I have a file func.cpp which provides 2 functions :
func.cpp:
int simple(void) {
return 12;
}
int call_lib(void) {
int res;
void *handle = dlopen("/home/jerome/Test/libDyn.so", RTLD_NOW);
if (!handle) {
return -1;
}
dlerror();
char* err = 0;
int (*fun_dyn)() = (int (*)())dlsym(handle, "fun_dyn");
if ( (err = dlerror()) != 0 ) {
dlclose(handle);
return -1;
}
res = (*fun_dyn)();
dlclose(handle);
return res;
}
It is created like that:
$ g++ -Wall -g -fPIC -c -o func.o func.cpp
$ ar rcs libFun.a func.o
I have a dynamic library which is called from call_lib() which depends
on libFun.a:
libDyn.cpp:
#include "func.hpp"
int fun_dyn(void) {
return simple();
}
It is created like that:
$ g++ -Wall -g -fPIC -c -o libDyn.o libDyn.cpp
$ g++ -Wall -g -fPIC -shared -o libDyn.so libDyn.o
I'm using swig to wrap the libFun.a library with this mylib.i interface
file:
%module mylib
int simple(void);
int call_lib(void);
Then I'm using this setup.py file to create the Python module:
from distutils.core import setup, Extension
mylib = Extension("_mylib",
sources=['mylib.i'],
language="c++",
extra_link_args=['-rdynamic'],
libraries=["Fun", "dl"],
)
setup(name="MyLib",
platforms=["Linux"],
ext_modules=[mylib],
py_modules = ["mylib"])
It's a simplified example but when I compile everything I get this error
in Python:
>>> import _mylib
>>> _mylib.call_lib()
failed to open shared object file
/home/jerome/Test/libDyn.so: undefined symbol: simple
If I do a nm _mylib.so I see that the symbol simple is present in the
library so I'm wondering why dlopen doesn't see it when it tries to load
the library.
I know I can recompile libDyn.so to link libFun.a but this would means I
would need to recompile all the plugins provided for the library I'm
trying to wrap and that's not really a solution for my project.
Sorry for the long email. I can provide a tar.gz of the source code if
needed.
Thanks for your help
Jerome
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