------- Comment #3 from kargl at gcc dot gnu dot org 2007-11-27 22:45 -------
(In reply to comment #2)
> (In reply to comment #1)
> > There is no bug here. You have explicitly disabled
> > range checking. This means that you no longer have
> > a limitation on range in constant folding. It may
> > be help to look at -fdump-parse-tree. YOu don't
> > have an Inf until you actually do the transfer.
> >
>
> In that case it's a wrong code bug.
No!
> With -fno-range-check you've told the
> compiler to produce +Infinity rather than an overflow error.
No! No!
It does not say to produce a +Infinity. It says to produce
whatever value fits into a floating point number with a
p-bit significand and exponential range of [-IMAX, IMAX]
where p depends on the type kind parameter and IMAX is either
INT_MAX or LONG_MAX. The internal representation of a
floating point constant is done with MPFR.
> Instead, it takes it upon itself to produce something other
> than what the source says [which is log(y), not log(some
> expression that may or may not be called y)].
No! No! No!
troutmask:kargl[205] cat a.f90
real, parameter :: y = exp(log(huge(y))+20)
real, parameter :: x = log(y)
print *, x, y
end
troutmask:kargl[206] gfc -fdump-parse-tree -fno-range-check a.f90
symtree: y Ambig 0
symbol y (REAL 4)(PARAMETER UNKNOWN-INTENT UNKNOWN-ACCESS UNKNOWN-PROC)
value: 1.65093201e47
symtree: x Ambig 0
symbol x (REAL 4)(PARAMETER UNKNOWN-INTENT UNKNOWN-ACCESS UNKNOWN-PROC)
value: 1.08722839e2
WRITE UNIT=6 FMT=-1
TRANSFER 1.08722839e2
TRANSFER 1.65093201e47
DT_END
Do you see +Infinity?
troutmask:kargl[209] cat a.f90
real, parameter :: x = 1. / 0.
print *, x
end
troutmask:kargl[210] gfc -fdump-parse-tree -fno-range-check a.f90
symtree: x Ambig 0
symbol x (REAL 4)(PARAMETER UNKNOWN-INTENT UNKNOWN-ACCESS UNKNOWN-PROC)
value: @Inf@
WRITE UNIT=6 FMT=-1
TRANSFER @Inf@
DT_END
If one doesn't understand what a compiler option does, then it would
be prudent not to use that option.
--
kargl at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |kargl at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34230
