Ice seems to not support client side multi processes.

I just wrote a very simple Ice application to produce the problem.

Slice file:
module Test
{
interface TestInterface
{
idempotent string hello();
};
};

Client code:
#include <Ice/Ice.h>
#include "hello.h"
#include <sys/wait.h>

int main(int argc, char **argv)
{
Ice::CommunicatorPtr comm;
comm = Ice::initialize(argc, argv);

std::string proxyconf = "TestInterface:tcp -h localhost -p 50000";
Ice::ObjectPrx base = comm->stringToProxy(proxyconf);
Test::TestInterfacePrx proxy = Test::TestInterfacePrx::checkedCast(base);
long l_child_pid = 0;
l_child_pid = fork ();
std::string output = proxy->hello();
if (l_child_pid == 0 )
{
exit(0);
}
int status = 0;
waitpid(l_child_pid, &status, 0);
std::cout << output << std::endl;
}

And if running the program, it is blocked forever.

Stack trace for the parent:
#0 0x007bc7a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
#1 0x0086447b in __waitpid_nocancel () from /lib/tls/libc.so.6
#2 0x0805ca4b in main (argc=1, argv=0xbfeebfd4) at /net/soft_scratch/users/mzhang/temp/ice/client.cpp:21

This is fine. The parent process is waiting for the child process.

Stack trace for the child process:
#0 0x007bc7a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
#1 0x00a3cb26 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/libpthread.so.0
#2 0x008aeb17 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/libc.so.6
#3 0x00d8b6f1 in IceInternal::Outgoing::invoke (this=0xbfeebc70) at ../../include/IceUtil/Cond.h:203
#4 0x08056d7f in IceDelegateM::Test::TestInterface::hello (this=0x882cff8, __context=0x0) at /net/soft_scratch/users/mzhang/temp/ice/hello.cpp:194
#5 0x0805698f in IceProxy::Test::TestInterface::hello (this=0x882cfc0, __ctx=0x0) at /net/soft_scratch/users/mzhang/temp/ice/hello.cpp:123
#6 0x0805cc57 in IceProxy::Test::TestInterface::hello (this=0x882cfc0) at /net/soft_scratch/users/mzhang/temp/ice/hello.h:118
#7 0x0805ca15 in main (argc=1, argv=0xbfeebfd4) at /net/soft_scratch/users/mzhang/temp/ice/client.cpp:15

It is blocked there forever on a Ice call.

Best Regards,
Michael

Try to call _exit() instead of exit(). For more information on how to use fork() with Ice, please have a look at this FAQ.

Thanks for your reply.

If you use Ice to create a user library and hope the library can be used everywhere, basically you have no control over how the user forks a process. That might be a problem.

Regards,

Michael

I'm afraid there's not much we can do about this. All libraries that create threads, open network connections, or use signal handlers have this problem. fork() cannot be made aware of such things so that it takes care of the necessary cleanup automatically.