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From: "anlauf at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/86277] Presence of optional arguments not recognized
 for zero length arrays
Date: Mon, 12 Jun 2023 20:32:20 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D86277

--- Comment #29 from anlauf at gcc dot gnu.org ---
(In reply to Mikael Morin from comment #28)
> (In reply to anlauf from comment #27)
> > (In reply to Mikael Morin from comment #25)
> > > (In reply to Mikael Morin from comment #24)
> > > > (In reply to Mikael Morin from comment #23)
> > > > >=20
> > > > > This regresses on pr108065.f90 (that's a few extra analyzer warni=
ngs),
> > > > > and on pr69955.f90 (that's one extra __builtin_malloc).
> > > >=20
> > > > This removes the regressions.  Not fully retested again.
> > > >=20
> > > Comment #23 is probably the more correct one.
> > > Comment #24 works because of the double temporary.  Even if the first
> > > temporary has NULL data component, the second one uses malloc
> > > unconditionally to set data, and the argument is seen as present.
> >=20
> > Are you sure that you haven't mixed up those two?
> >=20
> > When trying with my extended testcase, and looking at the tree dump,
> > I see a double temporary for the call
> >=20
> >     call i ([real:: y])
> >=20
> > where the data pointer to the first allocation is clobbered later.
> > So I would rather go with the version from comment #24.
> >=20
> Let's rephrase:
> When (or rather if) we manage to remove the double temporary, we'll regre=
ss
> with comment #24, not with comment #23.
> The reallocation remains by the way, it's only pushed one step away.
> Try this for example:
>=20
>     call i([real:: y, y])

I do see the reallocation, but in the case of the patch in #24 it is a
realloc of a NULL, which is well-defined nowadays.

But I do not see a regression.  On the contrary, every else seems unchanged.

>=20=20
> > If you don't object, I'll package the patch with testcases and submit.
>=20
> No problem, I think we are safe with the second temporary.

Besides the issue with one or two temporaries, is there anything else?=