[gcc r13-969] c++: new-expression is potentially constant in C++20

[gcc r13-969] c++: new-expression is potentially constant in C++20

[Marek Polacek]

https://gcc.gnu.org/g:2423f6548405185e256036df3d0ef3c13fd996c5

commit r13-969-g2423f6548405185e256036df3d0ef3c13fd996c5
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Jun 2 15:56:18 2022 -0400

    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.

Diff:
---
 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: