HELLO

thread_db returns td_thrhandle_t objects as handles
these are NOT OPAQUE
although the declaration says it is:

  /* The actual thread handle type.  This is also opaque.  */
  typedef struct td_thrhandle
  {
    td_thragent_t *th_ta_p;
    psaddr_t th_unique;
  } td_thrhandle_t;

go figure

GDB doesn't touch either, except one inconsequential time:

  molly:[src]$ grep -r 'th_\(ta_p\|unique\)' gdb
  gdb/linux-thread-db.c:  th.th_unique = 0;
  gdb/nat/glibc_thread_db.h:  td_thragent_t *th_ta_p;
  gdb/nat/glibc_thread_db.h:  psaddr_t th_unique;

So we can return just "psaddr_t th_unique" and use that as our "handle"

---

For td_thr_get_info GDB passes in a pointer to a td_thrinfo_t structure.
(which has lots of elements, grrr)
return a ton of values and let the caller fill in the struct?
this is where referencing functions by typed names will be handy...
for cross-core debugging the struct size&offsets might not be the same, so...

infinity-thread-db.c
collects new func notifications (per inferior? per whatever makes sense 
for thread-db?)
and provides 4 i8_thread_db_* functions which wrap all this
(into td_thrhandle_t stuff too?
with same signatures as libthread_db funcs)