I used launchpad to start a hello_client and hello_server.I closed hello_server and expected the call from hello_client could cause an ipc error ,because the target is not exist .

I modify the l4_ipc_call function in file ipc-l42-gcc-nopic.h

L4_INLINE l4_msgtag_t
l4_ipc_call(l4_cap_idx_t dest, l4_utcb_t *u,
            l4_msgtag_t snd_tag,
            l4_timeout_t timeout) L4_NOTHROW
{
l4_umword_t dummy1, dummy2, dummy3;
l4_msgtag_t rtag;

(void)u;
__asm__ __volatile__
    (L4_ENTER_KERNEL
     :
     "=d" (dummy3),
     "=D" (dummy1),
     "=c" (timeout),
     "=S" (dummy2),
     "=a" (rtag.raw)
     :
     "S" (0),
     "c" (timeout),
     "d" (dest | L4_SYSF_CALL),
     "a" (snd_tag.raw)
     :
     "memory", "cc" L4S_PIC_CLOBBER
     );

// add by wyq

    int ipc_error = l4_ipc_error(rtag,u);

    if(ipc_error==L4_IPC_ENOT_EXISTENT ||ipc_error==L4_IPC_RECANCELED)
    {
           outstring("Ipc not exist or canceled ");
    }

// end

return rtag;
}

outstring is defined in <l4/sys/kdebug.h>,i am sure it can be used here.

I can not get the output and i don't know why.

Thanks & Regards