cvs commit: src/sys/sys queue.h

[Joseph Koshy]

> mux         2006-03-03 18:54:33 UTC
> 
>   FreeBSD src repository
> 
>   Modified files:
>     sys/sys              queue.h 
>   Log:
>   Cast the pointer to void * before casting it back to struct type * in
>   STAILQ_LAST.  This quiets a warning from GCC about increased required
>   alignment for the cast.
>   
>   Idea from:      cognet

Doesn't this trade a compile time warning for a runtime fault on those
architectures where alignment matters?

Which code triggers this warning? 

 274 #define STAILQ_LAST(head, type, field)                                 \
 275         (STAILQ_EMPTY((head)) ?                                        \
 276                 NULL :                                                 \
 277                 ((struct type *)                                       \
 278                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))

I can't see how this code would trigger a warning in normal usage.

Regards,
Koshy
<jkoshy at freebsd.org>