cvs commit: src/sys/vm vm_map.c

[Brian Fundakowski Feldman]

On Tue, Jun 29, 2004 at 08:02:48PM -0700, David Schultz wrote:
> On Wed, Jun 30, 2004, Bruce Evans wrote:
> > On Tue, 29 Jun 2004, Andrew Gallatin wrote:
> > 
> > > Bruce Evans writes:
> > >  > On Mon, 28 Jun 2004, Andrew Gallatin wrote:
> > >  > >  > > >   Log:
> > >  > >  > > >   Fix alpha - the use of min() on longs was loosing the high bits and
> > >  > >  > > >   returning wrong answers, leading to strange values vm2->vm_{s,t,d}size.
> > >  >
> > >  > MIN() and MAX() should not be used in the kernel.  4.4BSD removed them in
> > >  > the kernel, but FreeBSD broke this in rev.1.141 of sys/param.h.  They
> > >  > remain removed in RELENG_4.
> > >
> > > OK.  Then what's the correct fix? ulmin()?
> > 
> > Fixing min() to handle all unsigned types is probably best.
> 
> Hmm...but this means either
> 
> a) slightly pessimizing 32-bit ports with a function on uintmax_t's,
> 
> b) using a macro and introducing double-expansion problems, or
> 
> c) using GCC extensions
> 
> Option (c) seems best from a technical standpoint, except that
> we'd be making it harder than it already is to compile the kernel
> with compilers other than gcc and icc.  (Do others have the
> statement expr extension?)

No, the correct fix is using MIN() or MAX() that are well-documented
to provide the exact side-effects C programmers know to expect.  They
automatically return the correct type, too, with no coercion!

-- 
Brian Fundakowski Feldman                           \'[ FreeBSD ]''''''''''\
  <> green at FreeBSD.org                               \  The Power to Serve! \
 Opinions expressed are my own.                       \,,,,,,,,,,,,,,,,,,,,,,\