[PATCH]: Integrate gfortran with MPC

[Kaveh R. Ghazi]

From: "Kaveh R. Ghazi" <ghazi@caip.rutgers.edu>

> From: "Steve Kargl" <sgk@troutmask.apl.washington.edu>
>>
>> BTW, once mpc becomes mandatory, I plan to change gfc_expr as
>> follows:
>>
>> troutmask:sgk[225] diff -u gfortran.h.orig gfortran.h
>> --- gfortran.h.orig     2009-05-26 10:06:24.000000000 -0700
>> +++ gfortran.h  2009-05-26 10:09:03.000000000 -0700
>> @@ -1613,11 +1613,7 @@
>>
>>     mpfr_t real;
>>
>> -    struct
>> -    {
>> -      mpfr_t r, i;
>> -    }
>> -    complex;
>> +    mpc_t complex;
>>
>>     struct
>>     {

So I toyed with doing this conversion myself and the testcase
gfortran.dg/real_const_3.f90 started failing on lines 45 and 48.  I traced
it to the compile-time evaluation of these variables.  I think it happens in
gfc_arith_divide.

  complex :: z = (-0.1,-2.2)/(0.0,0.0)
  complex :: z2 = (0.1,1)/0

The above lines currently transform into NaN in gfortran and that's what the
testcase expects.  MPC, MPFR (and C) turn finite/zero into Inf.  Only
zero/zero turns into NaN.

I'm wondering if it was really meant for fortran to be different, or is this
a bug accidentally immortalized in the testcase?  I.e. what does the fortran
standard say?

        Thanks,
        --Kaveh