On Sat, Aug 02, 2014 at 12:09:24AM +0300, Janne Blomqvist wrote:
> > --- libgfortran/runtime/memory.c.jj 2014-06-18 08:50:33.000000000 +0200
> > +++ libgfortran/runtime/memory.c 2014-08-01 14:41:08.385856116 +0200
> > @@ -56,7 +56,9 @@ xmallocarray (size_t nmemb, size_t size)
> >
> > if (!nmemb || !size)
> > size = nmemb = 1;
> > - else if (nmemb > SIZE_MAX / size)
> > +#define HALF_SIZE_T (((size_t) 1) << (__CHAR_BIT__ * sizeof (size_t) / 2))
> > + else if (__builtin_expect ((nmemb | size) >= HALF_SIZE_T, 0)
> > + && nmemb > SIZE_MAX / size)
> > {
> > errno = ENOMEM;
> > os_error ("Integer overflow in xmallocarray");
>
> Nice, though as os_error() has the _Noreturn specifier the
> __builtin_expect() is not necessary, right? In libgfortran.h we have
The reason for __builtin_expect here was to make already the
nmemb > SIZE_MAX / size
computation as unlikely, the noreturn predictor will of course DTRT with the
{} block.
Jakub
