On 6/2/22 16:33, Marek Polacek wrote:
On Thu, Jun 02, 2022 at 04:26:27PM -0400, Jason Merrill wrote:
On 6/2/22 16:10, Marek Polacek wrote:
index 1346a1d4c10..2bbd8785627 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -9039,10 +9039,18 @@ potential_constant_expression_1 (tree t, bool 
want_rval, bool strict, bool now,
                  "before C++17");
         return false;
-    case DYNAMIC_CAST_EXPR:
-    case PSEUDO_DTOR_EXPR:
       case NEW_EXPR:
       case VEC_NEW_EXPR:
+      if (cxx_dialect >= cxx20)
+       /* In C++20, new-expressions are potentially constant.  */
+       return true;
+      else if (flags & tf_error)
+       error_at (loc, "new-expression is not a constant expression "
+                 "before C++20");
+      return false;
+
+    case DYNAMIC_CAST_EXPR:
+    case PSEUDO_DTOR_EXPR:
       case DELETE_EXPR:
       case VEC_DELETE_EXPR:

Delete, too.

Duh.  Fixed:

OK, thanks.

 From 2423f6548405185e256036df3d0ef3c13fd996c5 Mon Sep 17 00:00:00 2001
From: Marek Polacek <pola...@redhat.com>
Date: Thu, 2 Jun 2022 15:56:18 -0400
Subject: [PATCH] c++: new-expression is potentially constant in C++20

... so adjust p_c_e accordingly.

gcc/cp/ChangeLog:

        * constexpr.cc (potential_constant_expression_1): Treat
        {,VEC_}NEW_EXPR and {,VEC_}DELETE_EXPRas potentially constant in C++20.
---
  gcc/cp/constexpr.cc | 12 ++++++++++--
  1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 1346a1d4c10..684238883dc 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -9039,12 +9039,20 @@ potential_constant_expression_1 (tree t, bool 
want_rval, bool strict, bool now,
                  "before C++17");
        return false;
- case DYNAMIC_CAST_EXPR:
-    case PSEUDO_DTOR_EXPR:
      case NEW_EXPR:
      case VEC_NEW_EXPR:
      case DELETE_EXPR:
      case VEC_DELETE_EXPR:
+      if (cxx_dialect >= cxx20)
+       /* In C++20, new-expressions are potentially constant.  */
+       return true;
+      else if (flags & tf_error)
+       error_at (loc, "new-expression is not a constant expression "
+                 "before C++20");
+      return false;
+
+    case DYNAMIC_CAST_EXPR:
+    case PSEUDO_DTOR_EXPR:
      case THROW_EXPR:
      case OMP_PARALLEL:
      case OMP_TASK:

base-commit: 7b98910406b5000a6429c188b0c6cc14e3140637

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