topic Re: Shared libraries, threads and gethostbyname in Operating System - HP-UX

Shared libraries, threads and gethostbyname

Stanley Lewis_1 — Wed, 22 Jan 2003 22:15:07 GMT

Hi!

I'm trying to figure out why this code:

--------------------------------------
#include
#include
#include

extern "C"
{
void* test_thr(void* args)
{
cout << "-------------------------------" << endl;
cout << "Calling gethostbyname()" << endl;
hostent* host = gethostbyname("localhost");
cout << "host address is: " << host->h_name << endl;
cout << "errno is: " << errno << endl;
cout << "-------------------------------" << endl;
}
}

int do_test( void )
{
pthread_t tid;
pthread_create(&tid, NULL, test_thr, NULL);
pthread_join(tid, NULL);
}
--------------------------------------

Blocks on the gethostbyname() call when the above is put into a shared library and do_test() is called. Is there anything inherantly wrong with calling hostname lookup API's from the context of a thread created from a shared library that's been loaded into the main executable via shl_load()?

Thanks!

Re: Shared libraries, threads and gethostbyname

Mike Stroyan — Tue, 28 Jan 2003 21:33:52 GMT

It works fine for me in this small test program. Note that pthread should be the first system header included. All the files in the program and shared library should be compiled with aCC -mt or equivalent defines for threadsafe.

Re: Shared libraries, threads and gethostbyname

Stanley Lewis_1 — Tue, 28 Jan 2003 22:15:44 GMT

Hmmm... That does work better.

I can't tell, but I think my application is getting into a situation like the attached archive. In this case, I've got a global object that in turns makes the "do_test()" call. In this case the gethostbyname() call blocks...

Re: Shared libraries, threads and gethostbyname

Stanley Lewis_1 — Tue, 28 Jan 2003 22:16:23 GMT

BTW thanks for the code!

Re: Shared libraries, threads and gethostbyname

Mike Stroyan — Wed, 29 Jan 2003 17:51:00 GMT

That attachment is not readable.

Re: Shared libraries, threads and gethostbyname

Stanley Lewis_1 — Wed, 29 Jan 2003 17:55:08 GMT

I guess the forum doesn't like .tar.gz as an extension? Maybe this one will work. Thanks!