pthread_kill(0,0) Segmentation fault rather than ESRCH

[WaltSullivan]

The simple program:

#include <signal.h>
int
main (int arcg, char *argv[])
{
  pthread_kill((pthread_t)0,0);
  return 0;
}

Gets "Segmentation fault". The man page says it should return ESRCH. Looking at the eglibc-2.19 source I found:

In ./nptl/sysdeps/unix/sysv/linux/pthread_sigqueue.c
     27
     29 int
     30 pthread_sigqueue (threadid, signo, value)
     31 pthread_t threadid;
     32 int signo;
     33 const union sigval value;
     34 {
     35 #ifdef __NR_rt_tgsigqueueinfo
     36 struct pthread *pd = (struct pthread *) threadid;
     37
     38 /* Make sure the descriptor is valid. */
     39 if (DEBUGGING_P && INVALID_TD_P (pd))
     40 /* Not a valid thread handle. */
     41 return ESRCH;
     42

and in ./nptl/sysdeps/unix/sysv/linux/pthread_kill.c
     27 int
     28 __pthread_kill (threadid, signo)
     29 pthread_t threadid;
     30 int signo;
     31 {
     32 struct pthread *pd = (struct pthread *) threadid;
     33
     34 /* Make sure the descriptor is valid. */
     35 if (DEBUGGING_P && INVALID_TD_P (pd))
     36 /* Not a valid thread handle. */
     37 return ESRCH;
     38

and in ./ports/sysdeps/unix/bsd/bsd4.4/kfreebsd/fbtl/pthread_kill.c
     27 int
     28 __pthread_kill (threadid, signo)
     29 pthread_t threadid;
     30 int signo;
     31 {
     32 struct pthread *pd = (struct pthread *) threadid;
     33
     34 /* Make sure the descriptor is valid. */
     35 if (DEBUGGING_P && INVALID_TD_P (pd))
     36 /* Not a valid thread handle. */
     37 return ESRCH;
     38

In all of these cases, the "DEBUGGING_P &&" causes the "INVALID_TD_P (pd)" test to not be generated, since DEBUGGING_P is #defined as 0. We need to do the test!

The Ubuntu man page for pthread_kill says:

If sig is 0, then no signal is sent, but error checking is still performed; this can be used to check for the existence of a thread ID.

$ lsb_release -rd
Description: Ubuntu 14.04.3 LTS
Release: 14.04
$ apt-cache policy libc6
libc6:
  Installed: 2.19-0ubuntu6.6
  Candidate: 2.19-0ubuntu6.6
  Version table:
 *** 2.19-0ubuntu6.6 0
        500 http://ca.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu/ trusty-security/main amd64 Packages
        100 /var/lib/dpkg/status
     2.19-0ubuntu6 0
        500 http://ca.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages