[Bug libfortran/59774] [Regression] Inconsistent rounding between -m32 and -m64

[jvdelisle at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59774

Jerry DeLisle <jvdelisle at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Inconsistent rounding       |[Regression] Inconsistent
                   |between -m32 and -m64       |rounding between -m32 and
                   |                            |-m64

--- Comment #2 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> ---
I think this gets back to:

http://gcc.gnu.org/viewcvs/gcc?view=revision&revision=185433

Using:

 print "(ru,g11.2)", 99._8
 print "(ru,g11.2)", 99._4
end


Looking at the buffer in output_float we get:

$ gfc  -m32 pr59771.f90 
$ ./a.out 
buffer=+99900000000000000000000e+01<<<
   0.99E+02
buffer=+99.000000000000<<<
    10.    
$ gfc  -m64 pr59771.f90 
$ ./a.out 
buffer=+99900000000000000000000e+01<<<
   0.99E+02
buffer=+999000000000000e+01<<<
   0.99E+02

Notice the '.' in the buffer for kind=4 vs kind=8

I don't know all the reasons for the changes made, but think "." needs to get
stripped out before we ever get to output_float and the exponent needs to be
there.  I do recall the reason gfortran does its own rounding is because the C
implementations across platforms are not consistent.