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From: oliver.kowalke@t-online.de (Oliver Kowalke)
To: linux-kernel@vger.kernel.org
Subject: sendto generates SIGSEGV
Date: Sun, 29 Jul 2001 23:27:29 +0200
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Hi,

I've written an c++ class which wrappes a socket.. With function writen() 
you can write to an TCP and UDP socket ( TCP : pointer to stuct sockaddr == 
NULL; UDP :  pointer to struct sockaddr != NULL). If I use this function 
with TCP sockets all works. If I call this function for an UDP socket it 
generates an SIGSEGV signal.
What is wrong?

with regards,
Oliver

ssize_t writen( const void * vptr, size_t n, struct sockaddr * to)
{
        size_t          nleft = n;
        ssize_t         nwritten;
        const char      *ptr = static_cast< const char * >( vptr);
        
        struct sigaction new_sa;
        struct sigaction old_sa;
        
        new_sa.sa_handler = SIG_IGN;
        ::sigemptyset( & new_sa.sa_mask);
        new_sa.sa_flags = 0;
        ::sigaction( SIGPIPE, & new_sa, & old_sa);              

        while ( nleft > 0)
        {

                if ( ( nwritten = ::sendto( m_handle, ptr, nleft, 0, to, 
sizeof * to) 

)<=0)
                {
                        if ( errno == EINTR)
                                nwritten = 0;   // and call sendto() again
                        else if ( errno == EPIPE)
                        {
                                ::sigaction( SIGPIPE, & old_sa, 0);

                                return -1;              // write to sock with 
no readers (peer has the sock closed)

                        }
                        else
                        {
                                ::sigaction( SIGPIPE, & old_sa, 0);
                                throw; // error
                        }
                }

                nleft -= nwritten;
                ptr   += nwritten;
        }
        ::sigaction( SIGPIPE, & old_sa, 0);     // set to its previous action

        return n;
}

here the output of the generated core file:

Core was generated by 'lt-ogx 192.168.1.3 10000'.
Program terminated with signal 11, Segmentation fault.
rw_common (): write: Success.
warning: unable to get global thread event mask
[New Thread 1024 (LWP 32350)]
rw_common (): write: Success.
warning: stop_or_attach_thread: generic error
#0 0x0 in ?? ()