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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 13:30:23 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99456

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Another thing is that perhaps we should be rejecting reinterpret_cast only =
in
the
pedantic constant expression evaluation mode, not when we allow extensions =
and
fold as much as we can.  So something like (incremental):
--- gcc/cp/constexpr.c  2021-03-08 13:08:49.944229227 +0100
+++ gcc/cp/constexpr.c  2021-03-08 14:23:01.263716186 +0100
@@ -6629,11 +6629,9 @@

     case NOP_EXPR:
     case CONVERT_EXPR:
-      if (REINTERPRET_CAST_P (t))
+      if (REINTERPRET_CAST_P (t) && !ctx->quiet)
        {
-         if (!ctx->quiet)
-           error_at (loc,
-                     "%<reinterpret_cast%> is not a constant expression");
+         error_at (loc, "%<reinterpret_cast%> is not a constant expression=
");
          *non_constant_p =3D true;
          return t;
        }
@@ -8103,13 +8101,6 @@

     case NOP_EXPR:
     case CONVERT_EXPR:
-      if (REINTERPRET_CAST_P (t))
-       {
-         if (flags & tf_error)
-           error_at (loc, "%<reinterpret_cast%> is not a constant
expression");
-         return false;
-       }
-      /* FALLTHRU */
     case VIEW_CONVERT_EXPR:
       /* -- a reinterpret_cast.  FIXME not implemented, and this rule
         may change to something more specific to type-punning (DR 1312).  =
*/

But that doesn't make these inline vars statically initialized either, real=
ly
confused on what's going on.=