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.
Thanks,
Andrey Smirnov
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