[J3] Question not just for HPC

Malcolm Cohen malcolm at nag-j.co.jp
Wed Oct 16 04:13:56 EDT 2019

Hi folks,


The following program:


Program co428

  Use Iso_Fortran_Env

  Type(lock_type),Target :: p[*]

  Type lockpointer

    Type(lock_type),Pointer :: q

  End Type

  Type(lockpointer) x

  x%q => p


  Print *,'Is this really ok?'

End Program


is rejected by several compilers, usually with obviously-bogus messages,
like claiming that a pointer assignment is a variable definition context (it
is not).


I note that:

1.	Type lockpointer does not have a potential subobject component of
2.	That means X does not have to be a coarray.
3.	In the LOCK statement, the lock variable is not a coarray (though it
is pointer-associated with a coarray).
4.	Compiler opinions to the contrary, I can find no reason to say this
program is not conforming. It's possible that I've missed something.


Being able to lock and unlock local coarrays via a pointer is not very
exciting, but it is not nothing.


Have I missed something that would make this program invalid according to
our current standard? Please let me know where to find the rule if so.


Anyway, assuming that I didn't miss a rule making this invalid, I am not
raising an interp request at this time (I have a long list of other things
wrong with coarrays that I must get around to making interps for!). However
I am interested in hearing opinions as to whether this is an "obvious defect
in the standard", or an "obvious compiler bug". Reasonings or motivation for
the first opinion please (if the program really is valid by the current
standard, that is a good enough reason to call it a compiler bug).




..............Malcolm Cohen, NAG Oxford/Tokyo.


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