Messages in this thread | | | Date | Tue, 1 Sep 2020 15:21:58 +0300 | From | Dan Carpenter <> | Subject | Re: Fwd: Re: [PATCH] staging: gdm724x: gdm_tty: corrected macro by adding brackets |
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On Tue, Sep 01, 2020 at 02:06:23PM +0200, antoni.przybylik@wp.pl wrote: > On 01.09.2020 13:08, Greg KH wrote: > > On Tue, Sep 01, 2020 at 12:43:11PM +0200, antoniprzybylik wrote: > > > Such macros are dangerous. Consider following example: > > > #define GDM_TTY_READY(gdm) (gdm && gdm->tty_dev && gdm->port.count) > > > GDM_TTY_READY(a + b) > > > This macro will be expanded in such a way: > > > (a + b && a + b->tty_dev && a + b->port.count) > > > And it will lead to errors. > > This is for a pointer, no one would ever do that :) > > Nobody adds a pointer to a pointer, but it's common to add to it some value > like that: > > GDM_TTY_READY(myptr + 0x1000)
That won't compile at all, because it expands to "gdm + 0x1000->tty_dev".
> > > But, if you really worry about this, turn it into an inline function, > > that way you get the proper typedef safety, which is what something like > > this should really be, not a macro. > > How to do it? Do I need to send another patch?
Yeah. If you want. Or you could just find something else to patch. Probably just find a different bug and fix that instead... If at first you don't succeed, there are tons of other stuff to work on and maybe you will succeed there. ;)
regards, dan carpenter
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