Re: [RFC patches 05/13] util.h: Add BUILD_BUG_ON() and friends for compile-time assert checking

[Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>]

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On Fri, 2010-05-28 at 07:17 -0700, Marcel Holtmann wrote: 
> Hi Inaky,
> 
> > From: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
> > 
> > These have been stolen from the Linux kernel source; come pretty handy
> > to make build-time consistency checks and thus avoid run-time
> > surprises.
> > ---
> >  src/util.h |   29 +++++++++++++++++++++++++++++
> >  1 files changed, 29 insertions(+), 0 deletions(-)
> > 
> > diff --git a/src/util.h b/src/util.h
> > index 2835b76..cf34b67 100644
> > --- a/src/util.h
> > +++ b/src/util.h
> > @@ -77,3 +77,32 @@ unsigned char *pack_7bit(const unsigned char *in, long len, int byte_offset,
> >  				long *items_written, unsigned char terminator);
> >  
> >  char *sim_string_to_utf8(const unsigned char *buffer, int length);
> > +
> > +/*
> > + * Build time consistency checks
> > + *
> > + * Stolen from the Linux kernel 2.6.35-rc; as most taken from the
> > + * Linux kernel, this is licensed GPL v2 or newer.
> > + */
> > +
> > +/* Force a compilation error if condition is true */
> > +#define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_ZERO(condition))
> > +
> > +/* Force a compilation error if condition is constant and true */
> > +#define MAYBE_BUILD_BUG_ON(cond) ((void)sizeof(char[1 - 2 * !!(cond)]))
> > +
> > +/* Force a compilation error if a constant expression is not a power of 2 */
> > +#define BUILD_BUG_ON_NOT_POWER_OF_2(n)			\
> > +	BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
> > +
> > +/* Force a compilation error if condition is true, but also produce a
> > +   result (of value 0 and type size_t), so the expression can be used
> > +   e.g. in a structure initializer (or where-ever else comma expressions
> > +   aren't permitted). */
> > +#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
> > +#define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); }))
> > +
> > +/*
> > + * End of code stolen from the Linux kernel 2.6.35-rc. From now, code
> > + * is GPL v2 only.
> > + */
> 
> sounds like a nice addition, but src/util.h is the wrong file. I prefer
> we make this compatible so that it can be applied to ConnMan and BlueZ
> as well.
> 
> I think something like include/bug.h is better.

Sounds ok to me. Denis?