*Ping* patch, fortran] Warn about constant integer divisions

[Thomas Koenig]

Am 24.06.2015 um 22:21 schrieb Harald Anlauf:

> A truncation warning is pointless for expressions like 4/2 or
> n*(n+1)/2 with n an integer parameter.

To get more of a consensus, this version of the patch adds a
new warning option, to be included with -Wall, called
-Winteger-division, and only warns for when something is
truncated.

So, no warning with n*(n+1)/2, but a warning with 3/5.

So, OK for trunk?

	Thomas

2015-06-13  Thomas Koenig  <tkoenig@gcc.gnu.org>

        * arith.c (gfc_arith_divide):  With -Winteger-division,
        warn about contant integer division if there is a non-zero
        remainder.
        * invoke.texi:  Document -Winteger-division.
        * lang.opt:  Add -Winteger-division.

2015-06-13  Thomas Koenig  <tkoenig@gcc.gnu.org>

        * gfortran.dg/warn_conversion_8.f90:  New test.


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