Re: Newbie idiotic questions.

[Geert Uytterhoeven]

On Sun, 17 Jun 2001, Jeff Garzik wrote:
> David Flynn wrote:
> > > Daniel Phillips wrote:
> > > > Yep, the only thing left to resolve is whether Jeff had coffee or not.
> > ;-)
> > > >
> > > > -       if ((card->mpuout = kmalloc(sizeof(struct emu10k1_mpuout),
> > GFP_KERNEL))
> > > > +       if ((card->mpuout = kmalloc(sizeof(*card->mpuout), GFP_KERNEL))
> > >
> > > Yeah, this is fine.  The original posted omitted the '*' which was not
> > > fine :)
> > 
> > The only other thing left to ask, is which is easier to read when glancing
> > through the code, and which is easier to read when maintaining the code.
> > imho, ist the former for reading the code, i dont know about maintaing the
> > code since i dont do that, however in my own projects i prefere the former
> > when maintaing the code.
> 
> It's the preference of the maintainer.  It's a tossup:  using the type
> in the kmalloc makes the type being allocated obvious.  But using
> sizeof(*var) is a tiny bit more resistant to change.
> 
> Neither one sufficiently affects long term maintenance AFAICS, so it's
> personal preference, not any sort of kernel standard one way or the
> other...

The first one can be made a bit safer against changes by creating a `knew'
macro that behaves like `new' in C++:

| #define knew(type, flags)	(type *)kmalloc(sizeof(type), (flags))

If the types in the assignment don't match, gcc will tell you.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [e-mail]

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds