[patch, fortran] RFD: PR 56666 Allow suppression of zero-trip DO loop warning

[Janus Weil]

Hi Thomas,

> the rather self-explanatory patch implements the -Wzerotrip
> option.  The positive form is not really useful, because
> the option is on by default (so the default behavior is
> not changed).
>
> The negative form of the option, -Wno-zerotrip, suppresses the
> warning.  I have also added information of how to suppress the
> warning in the message.
>
> Alternatively, it is also possible to only activate the warning
> if it is set explicitly, or with -Wall.  I can easily change the
> patch to do so, if that turns out to be the consensus (I have no
> strong opinion on the matter either way)
>
> Regression-tested. OK for trunk?

I'm never quite sure whether I like the ongoing inflation of warning
options, but this particular flag is one that I might find useful
myself on occasion. So: Ok for trunk from my side.

However, I would prefer to disable the warning by default, but include
it in -Wall.

Thanks for the patch ...

Cheers,
Janus



> 2013-08-03  Thomas Koenig  <tkoenig@gcc.gnu.org>
>
>         PR fortran/56666
>         * gfortran.h (gfc_option_t):  Add warn_zerotrip.
>         * invoke.texi (-Wzerotrip):  Document option.
>         * lang.opt (Wzerotrip):  Add.
>         * options.c (gfc_init_options):  Initialize warn_zerotrip.
>         (gfc_handle_option):  Handle OPT_Wzerotrip.
>         * resolve.c (gfc_resolve_iterator): Honor
>         gfc_option.warn_zerotrip; update error message to show
>         how to suppress the warning.
>
> 2013-08-03  Thomas Koenig  <tkoenig@gcc.gnu.org>
>
>         PR fortran/56666
>         * gfortran.dg/do_check_10.f90:  New test.