Hi again,
On 24/01/2018 16:58, Paolo Carlini wrote:
Hi,
I'm looking into this rather mild regression, which should be
relatively easy to fix. In short, Jason's fix for c++/54325 moved an
abstract_virtuals_error_sfinae check from build_aggr_init_expr to
build_cplus_new therefore the testcase in this new bug isn't rejected
anymore because a special conditional for value-initialization from {
} in convert_like_real simply calls build_value_init and quickly
returns, thus build_cplus_new isn't involved. Thus I'm working on the
best way to add back the check. The below, which also uses
cp_unevaluated_operand, appears to work. Likewise something similar
inside build_value_init itself, which however seems too generic to me
(build_value_init is called in many other cases). I'm also not sure
about cp_unevaluated_operand, whether we need something more precise.
I'm gently "pinging" this message of mine... Definitely not an high
priority regression (in any case it's only a P3) but I'm still wondering
if we want to do something about the issue at this time. Lately I
noticed that in terms of testsuite even something as basic as the below
passes testing, not sure if we could consider it safe from a theoretical
point of view, however.
Thanks!
Paolo.
//////////////////////
Index: cp/call.c
===================================================================
--- cp/call.c (revision 257241)
+++ cp/call.c (working copy)
@@ -6765,6 +6765,8 @@ convert_like_real (conversion *convs, tree expr, t
&& TYPE_HAS_DEFAULT_CONSTRUCTOR (totype))
{
bool direct = CONSTRUCTOR_IS_DIRECT_INIT (expr);
+ if (abstract_virtuals_error_sfinae (NULL_TREE, totype, complain))
+ return error_mark_node;
expr = build_value_init (totype, complain);
expr = get_target_expr_sfinae (expr, complain);
if (expr != error_mark_node)
Index: testsuite/g++.dg/cpp0x/abstract-default1.C
===================================================================
--- testsuite/g++.dg/cpp0x/abstract-default1.C (nonexistent)
+++ testsuite/g++.dg/cpp0x/abstract-default1.C (working copy)
@@ -0,0 +1,26 @@
+// PR c++/83796
+// { dg-do compile { target c++11 } }
+
+struct MyAbstractClass
+{
+ virtual int foo() const = 0;
+};
+
+struct TestClass
+{
+ TestClass(const MyAbstractClass& m = {}) // { dg-error "abstract type" }
+ : value_(m.foo()) {}
+
+ int value_;
+};
+
+int TestFunction(const MyAbstractClass& m = {}) // { dg-error "abstract type"
}
+{
+ return m.foo();
+}
+
+int main()
+{
+ TestClass testInstance; // { dg-error "abstract type" }
+ TestFunction(); // { dg-error "abstract type" }
+}
