[sane-devel] strange thread code?

[Jaeger, Gerhard]

Hi,

On Mittwoch, 31. Dezember 2003 18:10, m. allan noah wrote:
> i am converting the fujitsu backend to use sanei_thread instead of fork.

okay - good ;-)

>
> in reading the threading code, i found something that i dont understand,
> and was hoping someone who knows a bit more could explain it to me:

let's try.

> in the function sanei_thread_waitpid(), the #ifdef PTHREAD section always
> returns pid (around line 354). but farther down, in the #else section, the
> return val from the waitpid() call is returned (which is the pid on
> success, but 0 or -1 otherwise)
>
> so if you are calling sanei_thread_waitpid() and there is an error, you
> might, or might not, get a negative return value?

The idea is, that sanei_thread_waitpid should be some replacement for waitpid,
and if this waitpid fails, you should get back exactly the code it delivers...
Only the case ECHILD is handled different (guess it was because of some
internals in the plustek backend ;-) )
In case of the pthread_join stuff, there's no proper replacement for waitpid,
and that's why this part always returns the pid (maybe this can also be
done better, but currently I don't see any problems there)

So you can use sanei_thread_waitpid the same way you have used it in
your backend...

> am i not reading this code correctly?

no, you're reading it correctly...

Hope this helps a bit,
  Gerhard