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From: "marcel.jacobse at ewetel dot net" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug fortran/101135] Use of absent assumed-shape array argument as
 an actual argument for an optional dummy argument mistakenly flagged as error
 by UndefinedBehaviourSanitizer
Date: Sat, 26 Jun 2021 01:07:30 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101135

--- Comment #1 from Marcel Jacobse <marcel.jacobse at ewetel dot net> ---
With some bisecting I managed to track this down to commit
https://gcc.gnu.org/git/?p=3Dgcc.git;a=3Dcommit;h=3D243c288370fe51ba55c3a9e=
e61eb2a1a62cb1279
being the first "faulty" one.

>>From what I can tell the commit aimed to catch null pointer dereferences in
more cases. Not sure if this means that the commit made the check to broad =
so
that it generates false positives for this Fortran case. Or if gfortran per=
haps
generates intermediate representation that is not quite valid and is correc=
tly
flagged by UBSan.=