On Wed, Aug 22, 2018 at 05:01:41PM -0700, Andrey Smirnov wrote:
> On Wed, Aug 22, 2018 at 12:09 AM Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> wrote:
> >
> > On Mon, Aug 20, 2018 at 11:26:00PM -0700, Andrey Smirnov wrote:
> > > Returning !bbu_find_handler() from barebox_update_handler_exists()
> > > would return the opposite result from what the name of that funciton
> > > implies. Drop the "!" to make it behave as expected.
> > >
> > > Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
> > > ---
> > > common/bbu.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/common/bbu.c b/common/bbu.c
> > > index 11e44f4a7..69ccac68a 100644
> > > --- a/common/bbu.c
> > > +++ b/common/bbu.c
> > > @@ -151,7 +151,7 @@ bool barebox_update_handler_exists(struct bbu_data *data)
> > > if (!data->handler_name)
> > > return false;
> > >
> > > - return !bbu_find_handler(data->handler_name);
> > > + return bbu_find_handler(data->handler_name);
> >
> > As bbu_find_handler() returns a pointer maybe better '!!' or
> > bbu_find_handler() != NULL?
> >
>
> That shouldn't be necessary since barebox_update_handler_exists()
> returns bool(real type name is _Bool) which explicitly specifies that
> a cast of any scalar value to it would be normalized to 1 or 0 (as per
> C99 standard from whence it came). Otherwise you'd be able to end up
> in a situation where bool1 && bool2 && (bool1 != bool2) evaluates to
> true.
>
> To give you more concrete example, here's what the last portion of
> that function compiles to on AArch64:
>
> 2924: 97ffff5e bl 269c <bbu_find_handler>
> 2928: f100001f cmp x0, #0x0
> 292c: 1a9f07e0 cset w0, ne // ne = any
> 2930: f9400bf3 ldr x19, [sp, #16]
> 2934: a8c27bfd ldp x29, x30, [sp], #32
> 2938: d65f03c0 ret
> 293c: 52800020 mov w0, #0x1 // #1
> 2940: 17fffffc b 2930 <barebox_update_handler_exists+0x30>
> 2944: 52800000 mov w0, #0x0 // #0
> 2948: 17fffffa b 2930 <barebox_update_handler_exists+0x30>
>
> and on AArch32 (Thumb):
>
> 18e0: f7ff ff48 bl 1774 <bbu_find_handler>
> 18e4: 3000 adds r0, #0
> 18e6: bf18 it ne
> 18e8: 2001 movne r0, #1
> 18ea: bd10 pop {r4, pc}
> 18ec: 2001 movs r0, #1
> 18ee: e7fc b.n 18ea <barebox_update_handler_exists+0x1a>
>
> as you can see both cases already have code to explicitly convert the
> result of the function to 0/1.
>
> I am more than happy to add ether !! or != NULL if you still think
> that'd be better, it just I don't think it will have any practical
> effect.
For sure it doesn't have a practical effect, it's merely a sign to show
"I know I'm casting a pointer to bool". Probably I'm just used to add
an explicit cast there and it's just a matter of taste.
Sascha
--
Pengutronix e.K. | |
Industrial Linux Solutions | http://www.pengutronix.de/ |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
_______________________________________________
barebox mailing list
barebox@xxxxxxxxxxxxxxxxxxx
http://lists.infradead.org/mailman/listinfo/barebox
