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From: "dcb314 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug fortran/98904] valgrind error in gfc_trans_assignment_1 during
 bootstrap
Date: Wed, 03 Feb 2021 19:10:44 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98904

--- Comment #12 from David Binderman <dcb314 at hotmail dot com> ---
(In reply to Tobias Burnus from comment #11)
> It might be that some code optimizes converts

...

> It might be that the either the middle end of GCC does this optimization =
or
> that valgrind does this internally.

I don't understand very much of your reply, but if you can replace
your two mights with facts, that would be IMHO a step in the right directio=
n.

I replaced my existing fprintf code with slightly better code
on the obvious conditional:

  if (flag_coarray =3D=3D GFC_FCOARRAY_LIB)
  {
    fprintf( stderr, "flag_coarray %d\n", flag_coarray);
    fprintf( stderr, "lhs_caf_attr.codimension %d\n",
lhs_caf_attr.codimension);
    fprintf( stderr, "rhs_caf_attr.codimension %d\n",
rhs_caf_attr.codimension);
    fprintf( stderr, "lhs_caf_attr.allocatable %d\n",
lhs_caf_attr.allocatable);
    fprintf( stderr, "lhs_refs_comp %d\n", lhs_refs_comp);
    fprintf( stderr, "rhs_caf_attr.allocatable %d\n",
rhs_caf_attr.allocatable);
    fprintf( stderr, "rhs_refs_comp %d\n", rhs_refs_comp);
  }

and, surprisingly, the problem seems to have gone away.

Mind you, I did compile with -O2 this time, not -O3 as originally specified=
,=20
so it looks like I get dodgy results if I build the fortran compiler with -=
O3.=20
I will avoid this in future. Deeper minds might want to look into this prob=
lem
some more.=