On 11/13/22 01:45, Jakub Jelinek wrote:
On Fri, Nov 11, 2022 at 06:07:04PM +0100, Jakub Jelinek wrote:
The following patch on top of Marek's P2448 PR106649 patch
(mainly because that patch implements the previous __cpp_constexpr
feature test macro bump so this can't go in earlier; OT,
P2280R4 doesn't have any feature test macro?) implements this
simple paper.
Ok for trunk if it passes bootstrap/regtest and is voted into C++23?
Here is an updated patch that passed bootstrap/regtest, the only
change is another testcase tweak.
2022-11-13 Jakub Jelinek <ja...@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_maybe_constant_var_p static or thread_local vars for
C++23.
This was accepted as a DR, so it shouldn't be limited to C++23 mode.
Certainly it should be allowed in C++20 mode; I don't have a strong
opinion about C++14/17. Jonathan, do you?
(potential_constant_expression_1): Likewise.
gcc/testsuite/
* g++.dg/cpp23/constexpr-nonlit17.C: New test.
* g++.dg/cpp23/feat-cxx2b.C: Adjust expected __cpp_constexpr
value.
* g++.dg/ext/stmtexpr19.C: Don't expect an error for C++23 or later.
--- gcc/c-family/c-cppbuiltin.cc.jj 2022-11-11 17:14:52.021613271 +0100
+++ gcc/c-family/c-cppbuiltin.cc 2022-11-11 17:17:45.065265246 +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=202110L");
cpp_define (pfile, "__cpp_named_character_escapes=202207L");
cpp_define (pfile, "__cpp_static_call_operator=202207L");
--- gcc/cp/constexpr.cc.jj 2022-11-11 17:14:52.024613231 +0100
+++ gcc/cp/constexpr.cc 2022-11-11 17:16:54.384952917 +0100
@@ -7085,7 +7085,8 @@ 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_maybe_constant_var_p (r)))
{
if (!ctx->quiet)
{
@@ -9577,7 +9578,10 @@ potential_constant_expression_1 (tree t,
tmp = DECL_EXPR_DECL (t);
if (VAR_P (tmp) && !DECL_ARTIFICIAL (tmp))
{
- if (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp))
+ if (CP_DECL_THREAD_LOCAL_P (tmp)
+ && !DECL_REALLY_EXTERN (tmp)
+ && (cxx_dialect < cxx23
+ || !decl_maybe_constant_var_p (tmp)))
{
if (flags & tf_error)
constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
@@ -9585,7 +9589,9 @@ potential_constant_expression_1 (tree t,
"%<constexpr%> context", tmp);
return false;
}
- else if (TREE_STATIC (tmp))
+ else if (TREE_STATIC (tmp)
+ && (cxx_dialect < cxx23
+ || !decl_maybe_constant_var_p (tmp)))
{
if (flags & tf_error)
constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
--- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit17.C.jj 2022-11-11
17:59:59.972852793 +0100
+++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit17.C 2022-11-11
17:59:38.725141231 +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/feat-cxx2b.C.jj 2022-11-11 17:14:52.194610922
+0100
+++ gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C 2022-11-11 17:48:56.038865825
+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 2020-01-14 20:02:46.839608995
+0100
+++ gcc/testsuite/g++.dg/ext/stmtexpr19.C 2022-11-12 09:17:40.706245495
+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 } }
};
return &atest;
Jakub
