re PR c++/57979 (G++ accepts constant expression defined using floating point non-constexpr glvalue)
PR c++/57979
* init.c (decl_really_constant_value): Rename from
integral_constant_value.
(scalar_constant_value): Similar but limited to scalar results.
(decl_constant_value_safe): Remove.
(constant_value_1): Respect return_aggregate_cst_ok_p.
* typeck.c (decay_conversion): Use scalar_constant_value.
* call.c (convert_like_real): Likewise.
* cvt.c (ocp_convert): No need to check CLASS_TYPE_P.
* typeck.c (decay_conversion): Or ARRAY_TYPE.
* constexpr.c (struct constexpr_ctx): Add strict field.
(cxx_eval_constant_expression) [VAR_DECL]: Use it to select between
decl_constant_value and decl_really_constant_value.
(cxx_eval_outermost_constant_expr): Add strict parm.
(maybe_constant_init): Not strict.
(potential_constant_expression_1): Add strict parm.
Shorten most internal calls with RECUR macro.
* cp-tree.h, pt.c, semantics.c: Adjust.
From-SVN: r217814
