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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/99456] [11 regression] ABI breakage with some static
 initialization
Date: Mon, 08 Mar 2021 13:39:50 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99456

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I'm not misreading the testcase, I'm just reacting on the fact that my patch
changed the behavior of it and looking into related issues when analyzing w=
hy.
It is up to the compiler to decide if it can or can't optimize it.
The strange thing is that before my patch, it was actually triggerring the
now removed cxx_eval_outermost_constant_expression code:
  /* Technically we should check this for all subexpressions, but that
     runs into problems with our internal representation of pointer
     subtraction and the 5.19 rules are still in flux.  */
  if (CONVERT_EXPR_CODE_P (TREE_CODE (r))
      && ARITHMETIC_TYPE_P (TREE_TYPE (r))
      && TREE_CODE (TREE_OPERAND (r, 0)) =3D=3D ADDR_EXPR)
    {
      if (!allow_non_constant)
       error ("conversion from pointer type %qT "
              "to arithmetic type %qT in a constant expression",
              TREE_TYPE (TREE_OPERAND (r, 0)), TREE_TYPE (r));
      non_constant_p =3D true;
    }
but with allow_non_constant false.  Which means the call didn't return
(uintptr_t) &desc (the folded expression), but
(uintptr_t) (unsigned int *) descRef
(an unfolded one).  And strangely that one then led to no dynamic
initialization,
while the folded one doesn't.=