Re: [patch] PR93727 Fortran 2018: EX edit descriptor

On 2/3/26 11:48 AM, Harald Anlauf wrote:
> Hi Jerry!
> 
> On 2/2/26 22:42, Jerry D wrote:
>> On 2/2/26 12:28 PM, Harald Anlauf wrote:
>>> Hi Jerry!
>>>
>> --- snip ---
>>> Let's see:
>>>
>>> 13.7.2.3.6 EX editing
>>>
>>> The EXw.d and EXw.dEe edit descriptors indicate that the external field
>>> occupies w positions, except when w is zero in which case the processor
>>> selects the field width. The fractional part of the field contains d
>>> hexadecimal digits, except when d is zero in which case the processor
>>> selects the number of hexadecimal digits to be the minimum required so
>>> that the output field is equal to the internal value; ...
>>>
>>> But -0XF.FFFFFP+124 is shorter than -0X1.FFFFFEP+127, so I think
>>> you should recheck.  Sorry for the extra work ;-)
>>>
>>>>
>>
>> I am very aware of this. My interpretation is "in which case the processor
>> selects" the number of hexadecimal digits to be what ever minimum it chooses
>> to produce. Keep in mind this is using the built-in C functions to generate
>> the hex string so we do not have a bit string to deal with. The value is 
>> correct and it is the minimum the processor produces.
>>
>> Anyone else one to way in on this? I sure don't want to create custom code bit 
>> shift this.
> 
> Not sure if C is really a good reference.
> printf takes a double when one wants to pass a float.
> With 53 bits for a double with the leading one implicitly set
> one could be biased towards a leading 1 before the decimal point.
> 
> #include <stdio.h>
> #include <values.h>
> 
> int
> main()
> {
>    printf ("%A\n", -FLT_MAX);
>    printf ("%A\n",-0X1.FFFFFEP+127);
>    printf ("%A\n", -0XF.FFFFFP+124);
> }
> 
> -0X1.FFFFFEP+127
> -0X1.FFFFFEP+127
> -0X1.FFFFFEP+127
> 
> And Fortran does it better (shorter)... ;-)
> 
> Harald
> 

I have been researching how best to do this. In the meantime,
for the test cases I am thinking similar to the following:

! { dg-options "-cpp -std=gnu" }
! { dg-do run }
! pr93727 EX Format Specifiers, testing various kinds, default field widths
program main
   implicit none
   character(kind=1, len=48) :: s1
   real(4) :: r4
   real(8) :: r8

#ifdef __GFC_REAL_10__
   real(10) :: r10
#endif
   !real(16) :: r16
   r4 = -huge(1.0_4)
   r8 = -huge( 1.0_8)

#ifdef __GFC_REAL_10__
   r10= -huge(1.0_10)
#endif

   ! KIND=16 will be at a later phase
   !r16 = 1.0_16/3.0_16

   write(s1,"(EX0.0,'<')") r4
   if (s1.ne."-0X1.FFFFFEP+127<") stop 1
   write(s1,"(EX0.0,'<')") r8
   if (s1.ne."-0X1.FFFFFFFFFFFFFP+1023<") stop 2

#ifdef __GFC_REAL_10__
   write(s1,"(EX0.0,'<')") r10
   if (s1.ne."-0XF.FFFFFFFFFFFFFFFP+16380<") stop 3
#endif

   write(s1,"(EX0.0,'<')") 1.0_4/r4
   if (s1.ne."-0X1P-128<") stop 4
   write(s1,"(EX0.0,'<')") 1.0_8/r8
   if (s1.ne."-0X0.4P-1022<") stop 5

#ifdef __GFC_REAL_10__
   write(s1,"(EX0.0,'<')") 1.0_10/r10
   if (s1.ne."-0X2P-16385<") stop 6
#endif

   !write(*,"(EX0.0,'<')" r16
end program main