[PATCH] fortran/88342 -- interaction of -ffpe-trap and IEEE_VALUE
H.J. Lu
hjl.tools@gmail.com
Sun Dec 30 16:50:00 GMT 2018
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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