Re: [PATCH v4 9/9] bug.h: Convert BUILD_BUG{,_ON} to use BUILD_BUG_ON_MSG

Josh Triplett
2012-10-31T01:02:45Z

On Tue, Oct 30, 2012 at 08:19:05PM +0100, Borislav Petkov wrote:
> On Sun, Oct 28, 2012 at 03:57:15PM -0500, danielfsantos@att.net wrote:
> > Remove duplicate code by converting BUILD_BUG and BUILD_BUG_ON to just
> > call BUILD_BUG_ON_MSG. This not only reduces source code bloat, but
> > also prevents the possibility of code being changed for one macro and
> > not for the other (which was previously the case for BUILD_BUG and
> > BUILD_BUG_ON).
> >
> > Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
> > ---
> > include/linux/bug.h | 17 +++--------------
> > 1 files changed, 3 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/linux/bug.h b/include/linux/bug.h
> > index 3bc1ddf..b58ba51 100644
> > --- a/include/linux/bug.h
> > +++ b/include/linux/bug.h
> > @@ -81,14 +81,8 @@ struct pt_regs;
> > #ifndef __OPTIMIZE__
> > #define BUILD_BUG_ON(condition) __compiletime_error_fallback(condition)
> > #else
> > -#define BUILD_BUG_ON(condition) \
> > - do { \
> > - extern void __build_bug_on_failed(void) \
> > - __compiletime_error("BUILD_BUG_ON failed"); \
> > - __compiletime_error_fallback(condition); \
> > - if (condition) \
> > - __build_bug_on_failed(); \
> > - } while(0)
> > +#define BUILD_BUG_ON(condition) \
> > + BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
>
> Concatenating "condition" might not be very informative in all cases.
> For example:
>
> BUILD_BUG_ON(1);
>
> Having __LINE__ is good enough IMHO.

While it doesn't always help, it may help sometimes. Worst case,
BUILD_BUG_ON(1) gives you no less information than it did before; best
case, it gives you useful data.

- Josh Triplett