[J3] Question not just for HPC
longb at cray.com
Wed Oct 16 23:16:06 EDT 2019
> On Oct 16, 2019, at 5:25 PM, Malcolm Cohen via J3 <j3 at mailman.j3-fortran.org> wrote:
> Hi Bill,
> > Type locktype has a component of type lock_type (obviously). A subobject is just a part of an object that can be referenced (3.141), so the component is clearly a subobject of x. So, could you explain how the word “potential” makes the statement above true?
> Two things here:
> • The component is not a subobject of X except in pointer association contexts. The word “subobject” cannot be applied to types, only to objects, we have other terms that can be applied to types.
> • “potential subobject component” is a defined term that applies to types as well as objects. It explicitly excludes pointer components.
> > Having something pointer associated with a coarray does not make the pointer itself a coarray. Only being declared to be a coarray (having a codimension) makes something a coarray.
> Well yeah, that’s what I said – there’s no rule saying X has to be a coarray, and I noted that X%Q is not a coarray.
> There is no requirement in LOCK that the lock variable has to be a coarray.
Type(lock_type),Target :: p[*]
Type(lock_type),Pointer :: q
x%q => p
Print *,'Is this really ok?'
C1608 A named variable with declared type LOCK_TYPE shall be a coarray. A named variable with a noncoarray potential subobject component of type LOCK_TYPE shall be a coarray.
R1179 lock-stmt is LOCK ( lock-variable [ , lock-stat-list ] )
R1182 lock-variable is scalar-variable
C1182 (R1182) A lock-variable shall be of type LOCK_TYPE from the intrinsic module ISO_FORTRAN_ENV (126.96.36.199).
C852 An entity with the POINTER attribute shall not have the ALLOCATABLE, INTRINSIC, or TARGET attribute, and shall not be a coarray.
-> Because x%q is a pointer it cannot be a coarray.
So, the whole argument here seems to hinge on the fact that x%q is not a “named variable”. Since if it were, it would have to be a coarray. Also, the LOCK statement in the example is only locking a local lock. Which is very peculiar, but apparently allowed.
> ..............Malcolm Cohen, NAG Oxford/Tokyo.
Bill Long longb at cray.com
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