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Description of problem:
The definition of timer_settime(timerid,flags,value,ovalue) allows ovalue
to be NULL, in case the programmer doesn't care about the timer's previous
value.  In practice, however, using a NULL 4th argument will cause the
program to crash.


Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1. Create the following program:
cat > settime_error.c << EOF
#include <signal.h>
#include <stddef.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>

int
main ()
{
  timer_t timer;
  struct sigevent event;
  struct itimerspec timeout;
  int status = 0;

  event.sigev_notify = SIGEV_NONE;
  if (timer_create (CLOCK_REALTIME, &event, &timer) < 0) {
    perror ("timer_create");
    exit (1);
  }
  timeout.it_value.tv_sec = 30;
  timeout.it_value.tv_nsec = 0;
  timeout.it_interval.tv_sec = 0;
  timeout.it_interval.tv_nsec = 0;
  if (timer_settime (timer, 0, &timeout, NULL) < 0) {
    perror ("timer_settime");
    status = 1;
  }
  if (timer_delete (timer) < 0) {
    perror ("timer_delete");
    status = 1;
  }
  if (status == 0)
    puts ("Timer functions passed.");
  return status;
}
EOF

2. Compile as follows:
gcc -g -lrt -o settime_error settime_error.c

3. Run -- preferably using gdb.
gdb settime_error


Actual Results:  GNU gdb 5.0rh-5 Red Hat Linux 7.1
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This GDB was configured as "i386-redhat-linux"...
(gdb) run
Starting program: /home/trevin/eyrx/src/libc/tests/t_time/settime-error 
[New Thread 1024 (LWP 2306)]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 1024 (LWP 2306)]
__timer_thread_queue_timer (thread=0x0, insert=0x4002e680)
    at ../linuxthreads/sysdeps/pthread/timer_routines.c:112
112	../linuxthreads/sysdeps/pthread/timer_routines.c: No such file or
directory.
	in ../linuxthreads/sysdeps/pthread/timer_routines.c
(gdb) bt
#0  __timer_thread_queue_timer (thread=0x0, insert=0x4002e680)
    at ../linuxthreads/sysdeps/pthread/timer_routines.c:112
#1  0x4002bc7d in timer_settime (timerid=0, flags=0, value=0xbffff750, 
    ovalue=0x0) at ../linuxthreads/sysdeps/pthread/timer_settime.c:121
#2  0x080485f8 in main () at settime-error.c:24
#3  0x40054e5e in __libc_start_main (main=0x8048580 <main>, argc=1, 
    ubp_av=0xbffff824, init=0x80483bc <_init>, fini=0x8048690 <_fini>, 
    rtld_fini=0x4000d3c4 <_dl_fini>, stack_end=0xbffff81c)
    at ../sysdeps/generic/libc-start.c:129


Expected Results:  Timer functions passed.


Additional info:

If ovalue is given as a pointer instead of NULL, the program will not
crash.