On Fri, May 29, 2020 at 03:17:51PM -0400, Jason Merrill via Gcc-patches wrote:
> On 5/28/20 7:23 PM, Marek Polacek wrote:
> > Barry pointed out to me that our braced-init-list as a template-argument
> > extension doesn't work as expected when we aggregate-initialize. Thus
> > fixed by calling digest_init in convert_nontype_argument so that we can
> > actually convert the CONSTRUCTOR.
> >
> > I don't think we can call digest_init any earlier, and it needs to
> > happen before the call to build_converted_constant_expr.
>
> Or we could fix build_converted_constant_expr to allow it; aggregate
> list-initialization is a user-defined conversion sequence, so I tihnk it
> should be allowed as part of a converted constant expression.
Ah, nice. It works just fine. Here's the complete patch:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
Barry pointed out to me that our braced-init-list as a template-argument
extension doesn't work as expected when we aggregate-initialize. Since
aggregate list-initialization is a user-defined conversion sequence, we
allow it as part of a converted constant expression.
Co-authored-by: Jason Merrill <ja...@redhat.com>
gcc/cp/ChangeLog:
PR c++/95369
* call.c (build_converted_constant_expr_internal): Allow
list-initialization.
gcc/testsuite/ChangeLog:
PR c++/95369
* g++.dg/cpp2a/nontype-class38.C: New test.
---
gcc/cp/call.c | 4 ++-
gcc/testsuite/g++.dg/cpp2a/nontype-class38.C | 30 ++++++++++++++++++++
2 files changed, 33 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/nontype-class38.C
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 2b393f96e5b..3c97b9846e2 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -4348,7 +4348,7 @@ build_converted_constant_expr_internal (tree type, tree
expr,
and where the reference binding (if any) binds directly. */
for (conversion *c = conv;
- conv && c->kind != ck_identity;
+ c && c->kind != ck_identity;
c = next_conversion (c))
{
switch (c->kind)
@@ -4356,6 +4356,8 @@ build_converted_constant_expr_internal (tree type, tree
expr,
/* A conversion function is OK. If it isn't constexpr, we'll
complain later that the argument isn't constant. */
case ck_user:
+ /* List-initialization is OK. */
+ case ck_aggr:
/* The lvalue-to-rvalue conversion is OK. */
case ck_rvalue:
/* Array-to-pointer and function-to-pointer. */
diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-class38.C
b/gcc/testsuite/g++.dg/cpp2a/nontype-class38.C
new file mode 100644
index 00000000000..5b440fd1c9e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class38.C
@@ -0,0 +1,30 @@
+// PR c++/95369
+// { dg-do compile { target c++20 } }
+
+struct S {
+ int a;
+ int b;
+};
+
+struct W {
+ int i;
+ S s;
+};
+
+template <S p>
+void fnc()
+{
+}
+
+template<S s> struct X { };
+template<W w> struct Y { };
+
+void f()
+{
+ fnc<{ .a = 10, .b = 20 }>();
+ fnc<{ 10, 20 }>();
+ X<{ .a = 1, .b = 2 }> x;
+ X<{ 1, 2 }> x2;
+ // Brace elision is likely to be allowed.
+ Y<{ 1, 2, 3 }> x3;
+}
base-commit: 640e05e02b567fa5ccf4c207e6fc6c3e9a93b17c
--
Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA
