2022-11-18  Jakub Jelinek  <jakub@redhat.com>

gcc/c-family/
	* c-cppbuiltin.cc (c_cpp_builtins): Bump __cpp_constexpr
	value from 202207L to 202211L.
gcc/cp/
	* constexpr.cc (cxx_eval_constant_expression): Implement C++23
	P2647R1 - Permitting static constexpr variables in constexpr functions.
	Allow DECL_EXPRs of decl_constant_var_p static or thread_local vars
	for C++23.
	(potential_constant_expression_1): Similarly, except use
	decl_maybe_constant_var_p instead of decl_constant_var_p if
	processing_template_decl.
gcc/testsuite/
	* g++.dg/cpp23/constexpr-nonlit17.C: New test.
	* g++.dg/cpp23/constexpr-nonlit18.C: New test.
	* g++.dg/cpp23/feat-cxx2b.C: Adjust expected __cpp_constexpr
	value.
	* g++.dg/ext/stmtexpr19.C: Don't expect an error.
	* g++.dg/ext/stmtexpr25.C: New test.

--- gcc/c-family/c-cppbuiltin.cc.jj	2022-11-18 09:00:17.102704379 +0100
+++ gcc/c-family/c-cppbuiltin.cc	2022-11-18 09:32:00.389372850 +0100
@@ -1074,7 +1074,7 @@ c_cpp_builtins (cpp_reader *pfile)
 	  /* Set feature test macros for C++23.  */
 	  cpp_define (pfile, "__cpp_size_t_suffix=202011L");
 	  cpp_define (pfile, "__cpp_if_consteval=202106L");
-	  cpp_define (pfile, "__cpp_constexpr=202207L");
+	  cpp_define (pfile, "__cpp_constexpr=202211L");
 	  cpp_define (pfile, "__cpp_multidimensional_subscript=202211L");
 	  cpp_define (pfile, "__cpp_named_character_escapes=202207L");
 	  cpp_define (pfile, "__cpp_static_call_operator=202207L");
--- gcc/cp/constexpr.cc.jj	2022-11-18 09:00:17.108704295 +0100
+++ gcc/cp/constexpr.cc	2022-11-18 09:35:39.822342414 +0100
@@ -7098,7 +7098,8 @@ cxx_eval_constant_expression (const cons
 	    && (TREE_STATIC (r)
 		|| (CP_DECL_THREAD_LOCAL_P (r) && !DECL_REALLY_EXTERN (r)))
 	    /* Allow __FUNCTION__ etc.  */
-	    && !DECL_ARTIFICIAL (r))
+	    && !DECL_ARTIFICIAL (r)
+	    && (cxx_dialect < cxx23 || !decl_constant_var_p (r)))
 	  {
 	    if (!ctx->quiet)
 	      {
@@ -9586,7 +9587,10 @@ potential_constant_expression_1 (tree t,
 
     case DECL_EXPR:
       tmp = DECL_EXPR_DECL (t);
-      if (VAR_P (tmp) && !DECL_ARTIFICIAL (tmp))
+      if (VAR_P (tmp) && !DECL_ARTIFICIAL (tmp)
+	  && (cxx_dialect < cxx23 || (processing_template_decl
+				      ? !decl_maybe_constant_var_p (tmp)
+				      : !decl_constant_var_p (tmp))))
 	{
 	  if (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp))
 	    {
--- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit17.C.jj	2022-11-18 09:32:00.393372795 +0100
+++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit17.C	2022-11-18 09:32:00.393372795 +0100
@@ -0,0 +1,12 @@
+// P2647R1 - Permitting static constexpr variables in constexpr functions
+// { dg-do compile { target c++23 } }
+
+constexpr char
+test ()
+{
+  static const int x = 5;
+  static constexpr char c[] = "Hello World";
+  return *(c + x);
+}
+
+static_assert (test () == ' ');
--- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit18.C.jj	2022-11-18 09:32:00.394372781 +0100
+++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit18.C	2022-11-18 09:57:48.159986371 +0100
@@ -0,0 +1,49 @@
+// P2647R1 - Permitting static constexpr variables in constexpr functions
+// { dg-do compile { target c++14 } }
+
+constexpr int
+f1 (int x)
+{
+  if (x)
+    throw 1;
+  return 0;
+}
+
+constexpr int
+f2 ()
+{
+  static const int a = f1 (1);		// { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+  return 0;
+}
+
+constexpr int
+f3 ()
+{
+  static const int a = 5;		// { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+  return 0;
+}
+
+constexpr int
+f4 ()					// { dg-message "declared here" "" { target c++20_down } }
+{					// { dg-message "is not usable as a 'constexpr' function because:" "" { target c++23 } .-1 }
+  static const int a = f1 (1);		// { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+  return 0;				// { dg-error "'a' defined 'static' in 'constexpr' context" "" { target c++23 } .-1 }
+}
+
+constexpr int a4 = f4 ();		// { dg-error "called in a constant expression" }
+
+constexpr int
+f5 ()
+{
+  static const int a = f1 (0);		// { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+  return 0;
+}
+
+constexpr int
+f6 ()
+{
+  static const int a = f1 (0);		// { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+  return 0;
+}
+
+constexpr int a6 = f6 ();		// { dg-error "called in a constant expression" "" { target c++20_down } }
--- gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C.jj	2022-11-18 09:00:17.293701708 +0100
+++ gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C	2022-11-18 09:32:00.394372781 +0100
@@ -134,8 +134,8 @@
 
 #ifndef __cpp_constexpr
 #  error "__cpp_constexpr"
-#elif __cpp_constexpr != 202207
-#  error "__cpp_constexpr != 202207"
+#elif __cpp_constexpr != 202211
+#  error "__cpp_constexpr != 202211"
 #endif
 
 #ifndef __cpp_decltype_auto
--- gcc/testsuite/g++.dg/ext/stmtexpr19.C.jj	2022-11-18 09:00:17.367700673 +0100
+++ gcc/testsuite/g++.dg/ext/stmtexpr19.C	2022-11-18 09:43:20.682975254 +0100
@@ -8,7 +8,7 @@ const test* setup()
 {
   static constexpr test atest =
     {
-      ({ static const int inner = 123; &inner; }) // { dg-error "static" }
+      ({ static const int inner = 123; &inner; }) // { dg-error "static" "" { target c++20_down } .-1 }
     };
 
   return &atest;
--- gcc/testsuite/g++.dg/ext/stmtexpr25.C.jj	2022-11-18 09:43:08.505143556 +0100
+++ gcc/testsuite/g++.dg/ext/stmtexpr25.C	2022-11-18 09:44:39.672883560 +0100
@@ -0,0 +1,17 @@
+// PR c++/81073
+// { dg-options "" }
+// { dg-do compile { target c++11 } }
+
+struct test { const int *addr; };
+
+const test* setup()
+{
+  static constexpr test atest =
+    {
+      ({ static const int inner = (throw 1, 1); &inner; }) // { dg-error "static" "" }
+    };
+
+  return &atest;
+}
+
+int main(){}