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Re: [PATCH] fortran/88342 -- interaction of -ffpe-trap and IEEE_VALUE


On Fri, Dec 28, 2018 at 4:38 PM Jerry DeLisle <jvdelisle@charter.net> wrote:
>
> On 12/28/18 10:43 AM, Steve Kargl wrote:
> > Ping.
> >
> > On Mon, Dec 24, 2018 at 11:59:50AM -0800, Steve Kargl wrote:
> >> All,
> >>
> >> The IEEE modules and -ffpe-trap are to some extent orthogonal
> >> features of gfortran.  Unfortunately, some users have the
> >> expectation of using -ffpe-trap for debugging while also using only
> >> some of the mechanisms provided by the IEEE modules.  For example,
> >>
> >> % t.f90
> >>     program test
> >>        use, intrinsic :: ieee_arithmetic
> >>        real :: inf
> >>        inf = ieee_value(inf,  ieee_positive_inf)
> >>     end program test
> >> % gfc8 -o z -ffpe-trap=overflow t.f90 && ./z
> >> Floating exception (core dumped)
> >>
> >> The correct use of the module would be along the lines of
> >>
> >>     program test
> >>        use, intrinsic :: ieee_arithmetic
> >>        real :: inf
> >>        logical h
> >>        call ieee_get_halting_mode(ieee_overflow, h)       ! store halting mode
> >>        call ieee_set_halting_mode(ieee_overflow, .false.) ! no halting
> >>        inf = ieee_value(inf, ieee_positive_inf)
> >>        call ieee_set_halting_mode(ieee_overflow, h)       ! restore halting mode
> >>     end program test
> >>
> >> Technically (as I have done in the patch), the user should also
> >> use 'ieee_support_halting(ieee_overflow)', but that's just a detail.
> >>
> >> Now, IEEE_VALUE() is specifically included in the Fortran standard
> >> to allow it to provide qNaN, sNaN, +inf, and -inf (among a few other
> >> questionable constants).  The attached patch allows gfortran to
> >> generate an executable that does not abort with SIGFPE.
> >>
> >> 2018-12-24  Steven G. Kargl  <kargl@gcc.gnu.org>
> >>
> >>      PR fortran/88342
> >>      * ieee/ieee_arithmetic.F90: Prevent exceptions in IEEE_VALUE if
> >>      -ffpe-trap=invalid or -ffpe-trap=overflow is used.
> >>
> >> 2018-12-24  Steven G. Kargl  <kargl@gcc.gnu.org>
> >>
> >>      PR fortran/88342
> >>      * gfortran.dg/ieee/ieee_10.f90:  New test.
> >>
> >> Regression tested on i586-*-freebsd and x86_64-*-freebsd.  OK to commit?
> >>
>
> OK Steve, thanks.

The test fails on Linux/x86:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88639


-- 
H.J.


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