Re: Add function attribute to copy_from_user to warn for unchecked results

[Jakub Jelinek <jakub@redhat.com>]

On Tue, Sep 16, 2003 at 01:26:32AM -0700, Andrew Morton wrote:
> Arjan van de Ven <arjanv@redhat.com> wrote:
> >
> > Hi,
> > 
> > gcc 3.4 (CVS) has a new function attribute (warn_unused_result) that
> > will make gcc spit out a warning in the event that a "marked" function's
> > result is ignored by the caller.
> 
> Nice.

Note that for macros like get_user something like this should be used
(as the attribute is only for functions):

extern inline __must_check int check_int_result (int arg) { return arg; }

#define get_user(x,ptr)                                                 \
check_int_result ( ({							\
	int __ret_gu,__val_gu;                                          \
        switch(sizeof (*(ptr))) {                                       \
        case 1:  __get_user_x(1,__ret_gu,__val_gu,ptr); break;          \
        case 2:  __get_user_x(2,__ret_gu,__val_gu,ptr); break;          \
        case 4:  __get_user_x(4,__ret_gu,__val_gu,ptr); break;          \
        default: __get_user_x(X,__ret_gu,__val_gu,ptr); break;          \
        }                                                               \
        (x) = (__typeof__(*(ptr)))__val_gu;                             \
        __ret_gu;                                                       \
}) )

	Jakub