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From: Arno on 22 Sep 2009 11:19
Dear all,

Find below a piece of code that gives a run-time error with the ifort
compiler. I thought this to be legal code, but maybe I am overlooking
something.

Thanks in advance,

Arno

===========================
file 1 (main.f90)

program main
use my_module
call wrapper()
end program main

===========================

file 2 (my_module.f90)

module my_module

contains

subroutine wrapper(str)
character(9),intent(in),optional :: str
call show(str)
end subroutine wrapper

subroutine show(str)
character(9),intent(in),optional :: str
if (present(str)) write(*,*) str
end subroutine show

end module my_module

==========================

% ifort -V
Intel(R) Fortran Compiler Professional for applications running on
IA-32, Version 11.1 Build 20090630 Package ID: l_cprof_p_11.1.046
Copyright (C) 1985-2009 Intel Corporation. All rights reserved.
% ifort -traceback -ftrapuv -fp-stack-check -check all my_module.f90
main.f90
% a.out
forrtl: severe (408): fort: (18): Dummy character variable 'STR' has
length 9 which is greater then actual variable length 0

Image PC Routine Line Source
a.out 08093FED Unknown Unknown Unknown
a.out 08092DE5 Unknown Unknown Unknown
a.out 0805FDC8 Unknown Unknown Unknown
a.out 0804ADA9 Unknown Unknown Unknown
a.out 0804B078 Unknown Unknown Unknown
a.out 08049D19 my_module_mp_wrap 11
my_module.f90
a.out 08049F5C MAIN__ 5 main.f90
a.out 08049CB1 Unknown Unknown Unknown
libc.so.6 B7DAA455 Unknown Unknown Unknown
a.out 08049BC1 Unknown Unknown Unknown


From: Paul van Delst on 22 Sep 2009 12:17
Arno wrote:
> Dear all,
>
> Find below a piece of code that gives a run-time error with the ifort
> compiler. I thought this to be legal code, but maybe I am overlooking
> something.

What happens if you declare the string arguments as

character(*),intent(in),optional :: str

(which you should do all the time anyway)

?

cheers,

paulv

>
> Thanks in advance,
>
> Arno
>
> ===========================
> file 1 (main.f90)
>
> program main
> use my_module
> call wrapper()
> end program main
>
> ===========================
>
> file 2 (my_module.f90)
>
> module my_module
>
> contains
>
> subroutine wrapper(str)
> character(9),intent(in),optional :: str
> call show(str)
> end subroutine wrapper
>
> subroutine show(str)
> character(9),intent(in),optional :: str
> if (present(str)) write(*,*) str
> end subroutine show
>
> end module my_module
>
> ==========================
>
> % ifort -V
> Intel(R) Fortran Compiler Professional for applications running on
> IA-32, Version 11.1 Build 20090630 Package ID: l_cprof_p_11.1.046
> Copyright (C) 1985-2009 Intel Corporation. All rights reserved.
> % ifort -traceback -ftrapuv -fp-stack-check -check all my_module.f90
> main.f90
> % a.out
> forrtl: severe (408): fort: (18): Dummy character variable 'STR' has
> length 9 which is greater then actual variable length 0
>
> Image PC Routine Line Source
> a.out 08093FED Unknown Unknown Unknown
> a.out 08092DE5 Unknown Unknown Unknown
> a.out 0805FDC8 Unknown Unknown Unknown
> a.out 0804ADA9 Unknown Unknown Unknown
> a.out 0804B078 Unknown Unknown Unknown
> a.out 08049D19 my_module_mp_wrap 11
> my_module.f90
> a.out 08049F5C MAIN__ 5 main.f90
> a.out 08049CB1 Unknown Unknown Unknown
> libc.so.6 B7DAA455 Unknown Unknown Unknown
> a.out 08049BC1 Unknown Unknown Unknown
>
>
From: Gordon Sande on 22 Sep 2009 12:27
On 2009-09-22 13:17:54 -0300, Paul van Delst <paul.vandelst(a)noaa.gov> said:

> Arno wrote:
>> Dear all,
>>
>> Find below a piece of code that gives a run-time error with the ifort
>> compiler. I thought this to be legal code, but maybe I am overlooking
>> something.
>
> What happens if you declare the string arguments as
>
> character(*),intent(in),optional :: str
>
> (which you should do all the time anyway)
>
> ?
>
> cheers,
>
> paulv
>
>>
>> Thanks in advance,
>>
>> Arno
>>
>> ===========================
>> file 1 (main.f90)
>>
>> program main
>> use my_module
>> call wrapper()
>> end program main
>>
>> ===========================
>>
>> file 2 (my_module.f90)
>>
>> module my_module
>>
>> contains
>>
>> subroutine wrapper(str)
>> character(9),intent(in),optional :: str
>> call show(str)

Perhpas you meant

if ( present (str ) ) then
call show ( str )
else
call show ( )
end if

as the property of being present does not "pass through" in
the way you seem to expect.

>> end subroutine wrapper
>>
>> subroutine show(str)
>> character(9),intent(in),optional :: str
>> if (present(str)) write(*,*) str
>> end subroutine show
>>
>> end module my_module
>>
>> ==========================
>>
>> % ifort -V
>> Intel(R) Fortran Compiler Professional for applications running on
>> IA-32, Version 11.1 Build 20090630 Package ID: l_cprof_p_11.1.046
>> Copyright (C) 1985-2009 Intel Corporation. All rights reserved.
>> % ifort -traceback -ftrapuv -fp-stack-check -check all my_module.f90
>> main.f90
>> % a.out
>> forrtl: severe (408): fort: (18): Dummy character variable 'STR' has
>> length 9 which is greater then actual variable length 0
>>
>> Image PC Routine Line Source
>> a.out 08093FED Unknown Unknown Unknown
>> a.out 08092DE5 Unknown Unknown Unknown
>> a.out 0805FDC8 Unknown Unknown Unknown
>> a.out 0804ADA9 Unknown Unknown Unknown
>> a.out 0804B078 Unknown Unknown Unknown
>> a.out 08049D19 my_module_mp_wrap 11
>> my_module.f90
>> a.out 08049F5C MAIN__ 5 main.f90
>> a.out 08049CB1 Unknown Unknown Unknown
>> libc.so.6 B7DAA455 Unknown Unknown Unknown
>> a.out 08049BC1 Unknown Unknown Unknown


From: Richard Maine on 22 Sep 2009 12:30
Paul van Delst <paul.vandelst(a)noaa.gov> wrote:

> Arno wrote:

> > Find below a piece of code that gives a run-time error with the ifort
> > compiler. I thought this to be legal code, but maybe I am overlooking
> > something.

[code elided]
>
> What happens if you declare the string arguments as
>
> character(*),intent(in),optional :: str
>
> (which you should do all the time anyway)

While I agree with that as good advice, it does not relate to the
legality of the code. I see nothing wrong with the original code in
terms of the standard.

--
Richard Maine | Good judgment comes from experience;
email: last name at domain . net | experience comes from bad judgment.
domain: summertriangle | -- Mark Twain
From: Richard Maine on 22 Sep 2009 12:40
Gordon Sande <g.sande(a)worldnet.att.net> wrote:

> Perhpas you meant
>
> if ( present (str ) ) then
> call show ( str )
> else
> call show ( )
> end if
>
> as the property of being present does not "pass through" in
> the way you seem to expect.

Eh? I thought the standard went out of its way to be quite explicit that
it does pass through exactly like that. Otherwise, things rapidly get
very awkward when you extend the above workaround construct to multiple
optional arguments. Looks to me like the standard even repeats itself, I
suppose to make sure that the point comes across. See 12.4.1.6 of F2003
(and this same stuff is in f90 and f95 - not new to f2003),
"Restrictions on dummy arguments not present." First sentence of the
section:

"A dummy argument... is not present if the dummy argument...
(2) is associated with an actual argument that is not present."

In case someone missed that, the last sentence in the section says

"Except as noted in the list above, it [a dummy arg that is not
present] may be supplied as an actual argument corresponding to an
optional dummy argument, which is then also considered to be not
associated with an actual argument."

--
Richard Maine | Good judgment comes from experience;
email: last name at domain . net | experience comes from bad judgment.
domain: summertriangle | -- Mark Twain
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