Hi!
Non-type template arguments are constant-expression in the grammar and thus
manifestly constant-evaluated.
For e.g. class templates, convert_nontype_argument is called with
tf_warning_or_error and so while we called in the below spots
maybe_constant_value without manifestly_const_eval=true, there is a
if (TREE_CODE (expr) != INTEGER_CST
&& !value_dependent_expression_p (expr))
{
if (complain & tf_error)
{
int errs = errorcount, warns = warningcount + werrorcount;
if (!require_potential_constant_expression (expr))
expr = error_mark_node;
else
expr = cxx_constant_value (expr);
later on and cxx_constant_value will do the manifestly_const_eval=true.
On the testcase below with function template, complain is tf_none and
so we only call that maybe_constant_value and not cxx_constant_value.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?
2019-02-08 Jakub Jelinek <ja...@redhat.com>
PR c++/88977
* pt.c (convert_nontype_argument): Pass true as manifestly_const_eval
to maybe_constant_value calls.
* g++.dg/cpp2a/is-constant-evaluated7.C: New test.
--- gcc/cp/pt.c.jj 2019-02-05 10:04:19.038028029 +0100
+++ gcc/cp/pt.c 2019-02-08 09:46:23.370257199 +0100
@@ -6821,12 +6821,14 @@ convert_nontype_argument (tree type, tre
/* Make sure we return NULL_TREE only if we have really issued
an error, as described above. */
return (complain & tf_error) ? NULL_TREE : error_mark_node;
- expr = maybe_constant_value (expr);
+ expr = maybe_constant_value (expr, NULL_TREE,
+ /*manifestly_const_eval=*/true);
expr = convert_from_reference (expr);
}
else if (TYPE_PTR_OR_PTRMEM_P (type))
{
- tree folded = maybe_constant_value (expr);
+ tree folded = maybe_constant_value (expr, NULL_TREE,
+ /*manifestly_const_eval=*/true);
if (TYPE_PTR_P (type) ? integer_zerop (folded)
: null_member_pointer_value_p (folded))
expr = folded;
--- gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated7.C.jj 2019-02-08
09:53:47.255935430 +0100
+++ gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated7.C 2019-02-08
09:49:45.159957823 +0100
@@ -0,0 +1,18 @@
+// P0595R2
+// PR c++/88977
+// { dg-do compile { target c++11 } }
+
+namespace std {
+ constexpr inline bool
+ is_constant_evaluated () noexcept
+ {
+ return __builtin_is_constant_evaluated ();
+ }
+}
+
+template<bool B> constexpr bool foo () { return B; }
+
+constexpr bool x = foo<std::is_constant_evaluated ()> ();
+constexpr bool y = foo<__builtin_is_constant_evaluated ()> ();
+static_assert (x, "");
+static_assert (y, "");
Jakub
