On 7/19/24 12:24 PM, Patrick Palka wrote:
On Fri, 19 Jul 2024, Jason Merrill wrote:
On 7/19/24 10:55 AM, Patrick Palka wrote:
On Fri, Jul 5, 2024 at 1:50 PM Patrick Palka <ppa...@redhat.com> wrote:
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
OK for trunk/14?
-- >8 --
During the alias CTAD transformation, if substitution failed for some
guide we should just discard the guide silently. We currently do
discard the guide, but not silently, which causes us to reject the
below testcase due to forming a too-large array type when transforming
the user-defined deduction guides.
This patch fixes this by passing complain=tf_none instead of
=tf_warning_or_error in the couple of spots where we expect subsitution
to possibly fail and so subsequently check for error_mark_node.
Ping. Alternatively we could set complain=tf_none everywhere.
That sounds better, unless you think there's a reason to have different
complain args for different calls.
I was initially worried about a stray error_mark_node silently leaking
into the rewritten guide signature (since we don't check for
error_mark_node after each substitution) but on second thought that
seems unlikely. The substitution steps in alias_ctad_tweaks that
aren't checked should probably never fail, since they're just reindexing
template parameters etc.
So like so?
OK.
-- >8 --
Subject: [PATCH] c++: missing SFINAE during alias CTAD [PR115296]
PR c++/115296
gcc/cp/ChangeLog:
* pt.cc (alias_ctad_tweaks): Use complain=tf_none
instead of tf_warning_or_error.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/class-deduction-alias23.C: New test.
---
gcc/cp/pt.cc | 2 +-
.../g++.dg/cpp2a/class-deduction-alias23.C | 19 +++++++++++++++++++
2 files changed, 20 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/class-deduction-alias23.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 45453c0d45a..8e9951a9066 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -30298,7 +30298,7 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
(INNERMOST_TEMPLATE_PARMS (fullatparms)));
}
- tsubst_flags_t complain = tf_warning_or_error;
+ tsubst_flags_t complain = tf_none;
tree aguides = NULL_TREE;
tree atparms = INNERMOST_TEMPLATE_PARMS (fullatparms);
unsigned natparms = TREE_VEC_LENGTH (atparms);
diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias23.C
b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias23.C
new file mode 100644
index 00000000000..117212c67de
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias23.C
@@ -0,0 +1,19 @@
+// PR c++/115296
+// { dg-do compile { target c++20 } }
+
+using size_t = decltype(sizeof(0));
+
+template<class T, size_t N = size_t(-1)>
+struct span { span(T); };
+
+template<class T, size_t N>
+span(T(&)[N]) -> span<T, N>; // { dg-bogus "array exceeds maximum" }
+
+template<class T, size_t N>
+requires (sizeof(T[N]) != 42) // { dg-bogus "array exceeds maximum" }
+span(T*) -> span<T, N>;
+
+template<class T>
+using array_view = span<T>;
+
+array_view x = 0;
