Re: [PATCH] Fortran: function results never have the ALLOCATABLE attribute [PR109500]

[Steve Kargl <sgk@troutmask.apl.washington.edu>]

On Sat, Apr 22, 2023 at 05:17:30PM +0200, Mikael Morin wrote:
> Le 22/04/2023 à 15:52, Steve Kargl a écrit :
> > On Sat, Apr 22, 2023 at 11:25:41AM +0200, Mikael Morin wrote:
> > > 
> > > Le 20/04/2023 à 22:01, Harald Anlauf via Fortran a écrit :
> > > > Dear all,
> > > > 
> > > > Fortran 2018 added a clarification that the *result* of a function
> > > > whose result *variable* has the ALLOCATABLE attribute is a *value*
> > > > that itself does not have the ALLOCATABLE attribute.
> > > > 
> > > > For those interested: there was a thread on the J3 mailing list
> > > > some time ago (for links see the PR).
> > > > 
> > > > The patch which implements a related check was co-authored with
> > > > Steve and regtested by him.  Testcase verified against NAG.
> > > > 
> > > > OK for mainline (gcc-14)?
> > > > 
> > > Looks good in principle, but I think the real fix should be in the
> > > gfc_expr_attr function, which copies all the attributes (including
> > > allocatable) in the EXPR_FUNCTION case.  How would the testsuite react if
> > > that attribute was cleared there?  Is your patch still needed if
> > > gfc_expr_attr is fixed?
> > 
> > You may be correct that something can be done elsewhere.
> > I do note that a function result can be allocatable
> > (within the funciton body).  The issue only arises when
> > argument association is done, which is done where Harald
> > and I have the patch.  Do we know that the function will
> > be an actual argument associated with an allocatable
> > dummy argument when gfc_expr_attr is invoked?
> > 
> No, there is no context information in gfc_expr_attr, but the result should
> not be dependent on context anyway.
> 
> You are probably right that the impact of this bug is limited to the case of
> argument association, not as broad as I thought.  Yet we should not keep
> gfc_expr_attr returning an allocatable attribute for function expressions in
> any case.

I suspect we're stuck in a catch-22 situation.  The symbol is
marked as allocatable,

function foo()
   integer, allocatable :: foo
   foo = 42   !<--- So that this isn't rejected
end

but when the function is actually referenced in an expression
the result is normally used, and symbol is still marked as
allocatable.

-- 
Steve