dlopen/dlclose with static variables

[Joerg Budischewski <Joerg dot Budischewski at sun dot com>]

Hi,

I have problems with static variables in shared libraries. Have a look 
at the source at the end of this mail. I build it with

g++ -ldl -o main main.cxx
gcc -shared -o libso.so so.cxx

with a gcc 3.0.3 or with a gcc 2.95.2. Letting it run gives the 
following output:

opening shared library
calling symbol 0x40016920
Ctor 0x40017c00
leaving main
Segmentation fault (core dumped)

When I move the static object to the global scope (out of foo() ), the 
object gets only destructed once within dlclose(). The difference seems 
to be, that in the case shown below, a call to atexit() is generated by 
the compiler while in the latter case this is not done (proving with nm 
libso.so | grep atexit). I would consider the first behaviour to be bug.

Comments ? Any way to workaround this with different compiler/linker 
switches ?

Joerg Budischewski
[Open|Star]Office developer

--

so.cxx:
#include <stdio.h>

class A
{
public:
    A(){fprintf( stderr, "Ctor %p\n" , this );}
    ~A(){fprintf( stderr, "Dtor %p\n" , this );}
};

extern "C" void foo()
{
    static A a;
}


main.cxx:
#include <stdio.h>
#include <dlfcn.h>

typedef void ( * func ) ( void );

int main( int argc , char *argv[] )
{
    void * p;
    fprintf( stderr, "opening shared library\n" );
    p = dlopen( "libso.so" ,  RTLD_NOW );
    if( p )
    {
        func f = (func) dlsym( p , "foo" );
        if( f )
        {
            fprintf( stderr, "calling symbol %p\n" , f );
            f();
        }
        dlclose( p );
        fprintf( stderr, "leaving main\n" );
    }
    else
    {
        fprintf( stderr, "error: %s\n" , dlerror() );
    }
    return 0;
}