[J3] another PURE example

[Brad Richardson]

My point is that, if you're just trying to demonstrate that default initialization of a pointer component allows one to modify module variables within pure procedures, you don't need the extra type and the explicit constructor call to demonstrate that. Or have I missed some additional point your trying to make, or is there something else wrong with my example?

Regards,
Brad

On Tue, 2020-10-06 at 10:39 -0700, Robert Corbett wrote:

> My first example program was
> simpler. Someone proposed a
> solution to the problem as
> shown in the first program that
> does not work for the new
> program. I intend to include
> both programs in my interp
> request.
>
> The key difference between the
> programs is that the type
> definition for the type of the
> variable in the PURE subroutine
> does not include the default
> initialization.
>
> Robert Corbett
>
> On Oct 6, 2020, at 9:45 AM, Brad Richardson via J3 <j3 at mailman.j3-fortran.org> wrote:
>
>> Am I missing something, or would the following simpler example be sufficient to demonstrate the problem?
>>
>> MODULE V
>>
>> REAL, TARGET :: X = 1.0
>>
>> END
>>
>> MODULE PRINT
>>
>> USE V
>>
>> PRIVATE X
>>
>> CONTAINS
>>
>> SUBROUTINE PRINTX
>>
>> PRINT *, X
>>
>> END
>>
>> END
>>
>> MODULE T_M
>>
>> TYPE T
>>
>> REAL, POINTER :: P => X
>>
>> END
>>
>> END
>>
>> PURE SUBROUTINE SUBR
>>
>> USE T_M
>>
>> TYPE(T) Y
>>
>> Y%P = 2.0
>>
>> END
>>
>> PROGRAM MAIN
>>
>> USE PRINT
>>
>> CALL SUBR
>>
>> CALL PRINTX
>>
>> END
>>
>> Regards,
>> Brad
>>
>> On Mon, 2020-10-05 at 22:12 +0000, Robert Corbett via J3 wrote:
>>
>>> MODULE V
>>> REAL, TARGET :: X = 1.0
>>> END
>>>
>>> MODULE PRINT
>>> USE V
>>> PRIVATE X
>>> CONTAINS
>>> SUBROUTINE PRINTX
>>> PRINT *, X
>>> END SUBROUTINE PRINTX
>>> END
>>>
>>> MODULE T1
>>> TYPE T
>>> SEQUENCE
>>> REAL, POINTER :: P
>>> END TYPE T
>>> END
>>>
>>> MODULE T2
>>> USE V
>>> PRIVATE X
>>> TYPE T
>>> SEQUENCE
>>> REAL, POINTER :: P => X
>>> END TYPE T
>>> END
>>>
>>> PURE SUBROUTINE SUBR
>>> USE T1
>>> USE T2, TINIT => T
>>> TYPE(T) Y
>>> Y = TINIT()
>>> Y%P = 2.0
>>> END
>>>
>>> PROGRAM MAIN
>>> USE PRINT
>>> CALL SUBR
>>> CALL PRINTX
>>> END
>>> ================================================================
>>>
>>> I think the program above conforms to the Fortran 2018 standard,
>>> but I am not able to check its conformance. If anyone sees a
>>> mistake in it, please let me know.
>>>
>>> The program is another example of default initialization
>>> breaking the assumptions that underlie the PURE attribute.
>>> It shows that some of the fixes to the definition of PURE
>>> that were proposed in response to my first example are
>>> insufficient.
>>>
>>> Because only one compiler was able to compile my first example,
>>> I do not expect most compilers to be able to handle this
>>> program.
>>>
>>> I agree with Van that there are problems with the definition of
>>> PURE that go back to the original definition of PURE. Van also
>>> asserted that the addition of type extensions made the problems
>>> worse, but I do not understand what the additional problems
>>> are.
>>>
>>> Robert Corbett
>>>
>>> T
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