Re: libgomp and python: dlopen fails

[Sebastian Steiger <steigers at phys dot ethz dot ch>]

The interesting part of the output when LD_DEBUG=all is this:

    21475:     file=libgomp.so.1 [0];  generating link map
     21475:     symbol=dlerror;  lookup in file=python
     21475:     symbol=dlerror;  lookup in 
file=/usr/lib64/libpython2.3.so.1.0
     21475:     symbol=dlerror;  lookup in file=/lib64/tls/libpthread.so.0
     21475:     symbol=dlerror;  lookup in file=/lib64/libdl.so.2
     21475:     binding file /usr/lib64/libpython2.3.so.1.0 to 
/lib64/libdl.so.2: normal symbol `dlerror' [GLIBC_2.2.5]
     21475:     symbol=__dcgettext;  lookup in file=python
     21475:     symbol=__dcgettext;  lookup in 
file=/usr/lib64/libpython2.3.so.1.0
     21475:     symbol=__dcgettext;  lookup in 
file=/lib64/tls/libpthread.so.0
     21475:     symbol=__dcgettext;  lookup in file=/lib64/libdl.so.2
     21475:     symbol=__dcgettext;  lookup in file=/lib64/libutil.so.1
     21475:     symbol=__dcgettext;  lookup in file=/lib64/tls/libm.so.6
     21475:     symbol=__dcgettext;  lookup in file=/lib64/tls/libc.so.6
     21475:     binding file /lib64/libdl.so.2 to /lib64/tls/libc.so.6: 
normal symbol `__dcgettext' [GLIBC_2.2.5]
     21475:     symbol=__asprintf;  lookup in file=python
     21475:     symbol=__asprintf;  lookup in 
file=/usr/lib64/libpython2.3.so.1.0
     21475:     symbol=__asprintf;  lookup in 
file=/lib64/tls/libpthread.so.0
     21475:     symbol=__asprintf;  lookup in file=/lib64/libdl.so.2

< The rest is just python stuff for error handling and screen output.>



This encouraged me to take a sample C++ file for testing dlopen() which 
I found on the internet:


#include <iostream>
#include <dlfcn.h>
using namespace std;

int main()
{	
    void* handle = dlopen("(...)/libgomp.so.1", RTLD_LAZY);

    if (!handle) {
        cerr << "Cannot open library: " << dlerror() << '\n';
        return 1;
    }
    cout << "Loading was successful. Closing library...\n";
    dlclose(handle);
}



I compiled this file with g++4 -o dlopen_test.bin dlopen_test.cpp -ldl 
(I called the file dlopen_test.cpp) and got the following output:

"Cannot open library: (...)/libgomp.so.1: shared object cannot be 
dlopen()ed"


Obviously the output of the python shell was just dlerror(), but it is 
not very instructive.

I also tried RTLD_NOW instead of RTLD_LAZY, but the error was the same.