On 6/2/22 10:03, Marek Polacek wrote:
On Thu, Jun 02, 2022 at 08:42:36AM -0400, Patrick Palka wrote:
On Wed, 1 Jun 2022, Marek Polacek via Gcc-patches wrote:
Here we ICE because value_dependent_expression_p gets a NEW_EXPR
whose operand is a type, and we go to the default case which just
calls v_d_e_p on each operand of the NEW_EXPR. Since one of them
is a type, we crash on the new assert in t_d_e_p.
Looks like NEW_EXPR is considered to be not potentially constant
according to potential_constant_expression. I thought we shouldn't
be calling value_dependent_expression_p on such exprs?
Except in C++20 new-expressions are potentially constant, so the patch
is OK, and we should adjust pce1 accordingly.
I notice we currently fail to handle
struct A
{
int i;
constexpr A(int *p): i(*p) { delete p; }
};
constexpr int i = A(new int(42)).i;
though it does work inside a function.
You're correct. This is non-obvious: instantiation_dependent_expression_p
calls p_c_e before v_d_e_p, but the expression is CAST_EXPR<[NEW_EXPR]>,
where the [] denotes a TREE_LIST, created in cp_parser_functional_cast.
This TREE_LIST has no type. So p_c_e_1/CAST_EXPR goes to
9183 /* If this is a dependent type, it could end up being a class
9184 with conversions. */
9185 if (type == NULL_TREE || WILDCARD_TYPE_P (type))
9186 return true;
and returns true.
So we call v_d_e_p, which looks at the CAST_EXPR's op and sees a TREE_LIST,
so it calls any_value_dependent_elements_p, and we end up with a NEW_EXPR.
An alternative/more proper fix would be to fix p_c_e_1/CAST_EXPR. Maybe
by calling any_type_dependent_elements_p (which currently has no uses).
Thoughts?
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/new13.C
@@ -0,0 +1,11 @@
+// PR c++/105803
+// { dg-do compile }
+// { dg-additional-options "-fchecking=2" }
+
+namespace std {
+template <typename> class shared_ptr;
+}
+struct S {};
+template <int> void build_matrices() {
+ std::shared_ptr<S>(new S);
+}
I think this testcase might be IFNDR since shared_ptr<S> is incomplete
at the point of its non-dependent use.
Ah, overreduced. I've made shared_ptr complete.
Marek
