invalid threads ID

Hello, I´m implementing an multithread application under linux with
gcc and kdevelop. I use pthread library from linux to handle threads
and mutex. My question is how can my program detect if a thread struct
is still valid or active.... I use a library that call a function
pthread_kill (threadID,0) in order to detect if a thread is alive but
when the thread Id is invalid, it causes a segmentation fault.

Hello, I´m implementing an multithread application under linux with
gcc and kdevelop. I use pthread library from linux to handle threads
and mutex. My question is how can my program detect if a thread struct
is still valid or active.... I use a library that call a function
pthread_kill (threadID,0) in order to detect if a thread is alive but
when the thread Id is invalid, it causes a segmentation fault.
Last time I looked, pthread_t on Linux was an opaque type, a pointer to
an internal struct. So it may be non-null and still invalid.
Ex:
if (threadID==0)
return FALSE;