From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 43C923861916; Wed,  1 Jul 2020 19:31:15 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 43C923861916
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
 s=default; t=1593631875;
 bh=eODeHKQB20NtXugFF9pYUBB+UKpasFctR+R9EGU+dL4=;
 h=From:To:Subject:Date:In-Reply-To:References:From;
 b=eFsDK5t68otOrnbl3R6G2IWvMYsEBqlwfqNR22mlMw6RSli92c5lnnKUBit4SZcde
 eND7sHXv449T45b2voD9oQRv+TxjOp2tUVs/47gy7f/ZbwTJda6haHzzKUUKcSofgK
 fNU0ebV7iWpaa4Nr11ds7iXL1MYgtzLUBh6aGfHo=
From: "anlauf at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/96018] Optimization issue with external HDF5 library
Date: Wed, 01 Jul 2020 19:31:14 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: fortran
X-Bugzilla-Version: 10.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: anlauf at gcc dot gnu.org
X-Bugzilla-Status: WAITING
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-96018-4-L8W53KX8Ik@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-96018-4@http.gcc.gnu.org/bugzilla/>
References: <bug-96018-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <http://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <http://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Wed, 01 Jul 2020 19:31:15 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96018

--- Comment #5 from anlauf at gcc dot gnu.org ---
(In reply to martin.schlipf from comment #4)
> Finally, I reproduced it with gfortran 9.3.0 + hdf 1.12.0 and gfortran 10=
.0
> + hdf 1.10.4. With older versions of gfortran 7.3.0 it does not appear.

Workarounds:

- compile with -O0, not sure why this makes a difference

- or replace in write_real_array_nd:

    real,             intent(in) :: array(*)

by

    real                         :: array(*)



I'd recommend to additionally replace in write_complex_array_3d

   ierr =3D write_real_array_4d(locid, dataset_name, ptr)

by

   ierr =3D write_real_array_4d(locid, dataset_name, &
                              reshape (transfer(array,[1.0]),[2,
shape(array)]))

The latter is IMO much cleaner Fortran.

There might by a bug in gfortran with the way you use c_f_pointer and
assumed-size, which generates wrong code for argument packing, or there
is a bug elsewhere which may corrupt data subtly.=