dlopen try / catch failure

[Brian Hunt]

Hi everyone,

I cannot seem to catch errors either within or about objects opened with 
dlopen. See the code below for an example.  I am using gcc 3.0.2 et al., 
as follows (this problem occurs with gcc 3.2, as well, I believe):

address@hidden ~/tmp/dlopen]$  g++ -o y.o y.cc -c
address@hidden ~/tmp/dlopen]$  ld -E -shared y.o -o y.so
address@hidden ~/tmp/dlopen]$  g++ x.cc -Wl,-E -ldl -rdynamic
address@hidden ~/tmp/dlopen]$ ./a.out
 Registered rae
Aborted (core dumped)

In the example below, I am autoregistering components into a factory map 
(alpha) using the _init() symbol for on linkage execution.

x.h has the (abstract) interface class "doe", and the extern definition 
for the factory "alpha".  x.cc allocates space for the factory, and has 
a main function which iterates through the registered objects.  y.cc 
extends "doe", into the class "rae", and defines extern "C" symbols 
_init() which autoregisters the rae class and doe*Rae() which returns a 
new rae object.

The simple explicit try / throw / catch block within the "rae::hello()" 
function elucidates the issue I am having.  I have tried a number of 
linking and compiling options, but have yet to find a combination that 
solves this problem.

It is not even that there is failure passing a throw in a dlopen'ed 
symbol up to the main, although that fails too; the try/catch block is 
localized, yet still fails.

Any help would be greatly appreciated.

Cheers,
Brian



//---- x.h
#include #include 
#ifndef __DOE_
#define __DOE_
class doe {
    public:
    virtual string hello() = 0;
};

typedef doe* doe_t();
typedef map fact;
extern fact alpha;

#endif
//----/ x.h

//---- x.cc
#include 
#include 
#include 

using namespace std;
#include "x.h"

extern "C"{
    fact alpha;
}

int main(int argc, char**argv) {
    void * handle = dlopen("./y.so", RTLD_GLOBAL|RTLD_NOW);
    if (handle == NULL) {
        cerr << "Error opening y.so: " << dlerror() <::iterator sit = 
alpha.begin();
    for (; sit != alpha.end(); sit++) {
        doe * Y = alpha[sit->first]();
        std::cerr << " Registered " << sit->first << std::endl;
        std::cerr << " Hello: " << Y->hello() << std::endl;
    }

    dlclose(handle);
}

//----/ x.cc

//---- y.cc
#include 
#include 
#include using namespace std;
#include "x.h"

class rae : public doe {
    public:
    virtual string hello() {
        try {
                // remove this throw, and everything works.
            throw runtime_error("Why does this throw abort?");
            return "I am the lizard queen!";
        } catch (runtime_error &e) {
            cerr <<" Caught exception: " <<e.what() <<endl;
            return "exception caught";
        }
    }
};

extern "C" {
    doe * Rae() { return new rae(); }
    void _init() { alpha["rae"] = Rae; }
}
//----/ y.cc