Re: when can find_thread_pid (inferior_ptid) return NULL?

[Pedro Alves <pedro at codesourcery dot com>]

On Thursday 26 March 2009 21:36:42, Doug Evans wrote:
> Hi.  Some places in gdb assert that find_thread_pid (inferior_ptid)
> is never NULL.

> make_cleanup_restore_current_thread:
> 
>       tp = find_thread_pid (inferior_ptid);
>       if (tp)
> 	tp->refcount++;

I think that in this particular case, it will always be true.

> 
> Since delete_thread_1 has this:
> 
>   /* If this is the current thread, or there's code out there that
>      relies on it existing (refcount > 0) we can't delete yet.  Mark
>      it as exited, and notify it.  */
>   if (tp->refcount > 0
>       || ptid_equal (tp->ptid, inferior_ptid))
>     {
> 
> I would expect that one can always assert
> find_thread_pid (inferior_ptid) != NULL.
> 
> Is that true?
> Or are there situations where it's not true?

When inferior_ptid is null_ptid.  You'll also not
find the old ptid if running the cleanup after something
clears the thread list, e.g., after killing or poping the target.

-- 
Pedro Alves