Hi there William,

Why exactly is this not standard conforming? In the main program unit
he's calling Huge(x) where x is of type integer(4) and storing it in an
element of array b (also of integer(4)); and this is being passed to
dummy array "array" in the subroutine (yet again of integer(4)). When I
print (or use gdb) to view the contents of this variable it appears on
my machine to indeed be 2^n(machine dependent, I assume)-1.

Is there some bizzare quirk about the Huge() routine that I am missing?
I would have checked the definition in my copy of Modern Fortran
Explained or in the Standard but I am not at my work desk right now.

Cheers,
Adam Hirst

P.S. I was just about to send a message saying that by my reckoning, the
program should have indeed terminated with a result of 12 (with the
addition that the Function should of course have been defined as a
Subroutine, I guess that was just a typo.)

On 27/06/16 19:45, William Clodius wrote:
> The code with huge as array(2) is not standard conforming and gfortran can any of:
> 1. Not attempt to deal with the resulting overflow and generate the efficient code with the likely infinite runtime;
> 2. Insert a test for the overflow and generate a runtime error;
> 3. Insert a test for the overflow and kluge around the overflow as a special case giving the expected result; and
> 4. Treat i as integer(8) and not generate an overflow in spite of the type declaration.
> 
> There may of course be other options. I suspect ifort by default does 1 with the compiler switches used, while gfortran does 3 unless debugging switches are set, and does 2 with some combination of compiler debugging switches.
> 
>> On Jun 27, 2016, at 6:56 PM, Jan Hubicka <hubicka@ucw.cz> wrote:
>>
>> Hello,
>> I have a Fortran question.  The following program loops infinitly when compiled
>> with ifort -O0, while it does the expected number of iterations with gfortran.
>> The issue is that we do produce quite ineffective code to deal with
>> side cases like this.
>>
>> is the program bellow valid and expected to terminate?  If so I guess we want
>> to have it as a testcase.
>>
>> Thanks,
>> Honza
>>
>> program test_program
>> integer(4) :: b(2), a(22), x
>> integer(8) :: suma
>>
>> b(1) = huge(x)-10
>> b(2) = huge(x)
>>
>> call test2(b, suma)
>> print *,suma
>>
>> end program test_program
>> function test2(array, s)
>>  integer(4) :: i, block(9), array(2)
>>  integer (8) :: s
>>  s = 1
>>
>>  do i = array(1), array(2)
>>      s = s + 1
>>  end do
>>
>> end function test2
>>
> 

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