On Thu, Sep 20, 2018 at 11:56:37PM -0400, Marek Polacek wrote:
> The patch for P0595R1 - is_constant_evaluated had this hunk:
>
> @@ -5279,7 +5315,9 @@ maybe_constant_init_1 (tree t, tree decl, bool
> allow_non_constant)
> else if (CONSTANT_CLASS_P (t) && allow_non_constant)
> /* No evaluation needed. */;
> else
> - t = cxx_eval_outermost_constant_expr (t, allow_non_constant, false,
> decl);
> + t = cxx_eval_outermost_constant_expr (t, allow_non_constant,
> + !allow_non_constant,
> + pretend_const_required, decl);
> if (TREE_CODE (t) == TARGET_EXPR)
> {
> tree init = TARGET_EXPR_INITIAL (t);
>
> the false -> !allow_non_constant change means that when calling
> cxx_constant_init strict will be true because cxx_constant_init does not allow
> non constants. That means that for VAR_DECLs such as __func__ we'll call
> decl_really_constant_value instead of decl_constant_value. But only the
> latter
> can evaluate __func__ to "foo()".
>
> Jakub, was there a specific reason for this change? Changing it back still
> regtests cleanly and the attached test compiles again.
It just didn't feel right that cxx_constant_init which looks like a function
that requires strict conformance still passes false as strict.
If there is a reason to pass false, I think we need a comment that explains
it.
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2018-09-20 Marek Polacek <pola...@redhat.com>
>
> PR c++/87372 - __func__ constexpr evaluation.
> * constexpr.c (maybe_constant_init_1): Pass false for strict down to
> cxx_eval_outermost_constant_expr.
>
> * g++.dg/cpp1y/func_constexpr2.C: New test.
>
> diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c
> index fdea769faa9..6436b2f832d 100644
> --- gcc/cp/constexpr.c
> +++ gcc/cp/constexpr.c
> @@ -5361,7 +5361,7 @@ maybe_constant_init_1 (tree t, tree decl, bool
> allow_non_constant,
> /* No evaluation needed. */;
> else
> t = cxx_eval_outermost_constant_expr (t, allow_non_constant,
> - !allow_non_constant,
> + /*strict*/false,
> pretend_const_required, decl);
> if (TREE_CODE (t) == TARGET_EXPR)
> {
Jakub
