https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53277
--- Comment #19 from Jonathan Wakely <redi at gcc dot gnu.org> ---
For C++ the comment 15 case seems to have been fixed by r10-6527:
c++: Use constexpr to avoid wrong -Wsign-compare (PR90691).
We would like to do constexpr evaluation to avoid false positives on
warnings, but constexpr evaluation can involve function body copying that
changes DECL_UID, which breaks -fcompare-debug. So let's remember
that we need to avoid that.
PR c++/90691
* expr.c (fold_for_warn): Call maybe_constant_value.
* constexpr.c (struct constexpr_ctx): Add uid_sensitive field.
(maybe_constant_value): Add uid_sensitive parm.
(get_fundef_copy): Don't copy if it's true.
(cxx_eval_call_expression): Don't instantiate if it's true.
(cxx_eval_outermost_constant_expr): Likewise.
But it still warns when compiled as C.
