https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107819
--- Comment #6 from Mikael Morin <mikael at gcc dot gnu.org> --- (In reply to anlauf from comment #5) > (In reply to Mikael Morin from comment #4) > > But is it required to generate a temporary? > > As I understand it, the code is invalid, and (correctly) diagnosed, so there > > is nothing else to do. > > It's invalid because of 15.5.2.13 Restrictions on entities associated with > > dummy arguments: > > (4) If the value of the entity or any subobject of it is affected through > > the dummy argument, then at any time during the invocation and execution of > > the procedure, either before or after the definition, it shall be referenced > > only through that dummy argument unless (...) > > Right. > > I was confused by two observations. First, NAG & Cray seem to generate > temporaries, while Intel and NVidia don't and would agree with gfortran > after the patch. > > Second, I stumbled over: > > ! 15.5.2.3 Argument association > ! (4) A present dummy argument with the VALUE attribute becomes argument > ! associated with a definable anonymous data object whose initial value is > ! the value of the actual argument. > Ouch! You're right, this makes the part I quoted above irrelevant. And it explicitly asks for a temporary. > So it boils down to what ELEMENTAL actually means in that context. F2018: > > 15.8.3 Elemental subroutine actual arguments > > ! In a reference to an elemental subroutine, if the actual arguments > ! corresponding to INTENT(OUT) and INTENT(INOUT) dummy arguments are > ! arrays, the values of the elements, if any, of the results are the same > ! as would be obtained if the subroutine had been applied separately, in > ! array element order, to corresponding elements of each array actual > ! argument. > > So I read this that > > call s (a(n), a) > > is to be interpreted as > > do i = 1, size (a) > call s (a(n(i)), a(i)) > end do > > and this would actually be well-defined behavior... ;-) With your quote from 15.5.2.3 above, it would be more like: do i = 1, size(a) tmp(i) = a(n(i)) end do do i = 1, size(a) call s(tmp(i), a(i)) end do
