Hi!
I've totally missed the P3491R3 paper (define_static_{string,object,array})
comes with its own feature test macro - __cpp_lib_define_static 202506
which should appear in <version> and <meta>.
The paper contains 3 parts, std::is_string_literal,
std::meta::reflect_constant_{string,array} and
std::define_static_{string,object,array}.
The first part is implementable without reflection, the third part in theory
would be also implementable without reflection but usually will be (and in
libstdc++ is) implemented using reflection, and the middle part is really
part of reflection. So dunno how useful this FTM actually is, maybe just
for cases where some implementation does implement reflection and doesn't
implement this paper for a while.
Anyway, the FTM is in C++26 draft, so this patch adds it, with the same
condition as __cpp_lib_reflection.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2026-02-03 Jakub Jelinek <[email protected]>
PR libstdc++/123921
* include/bits/version.def (define_static): New with the
same values as reflection.
* include/bits/version.h: Regenerate.
* include/std/meta: Define also __glibcxx_want_define_static before
including bits/version.h.
* g++.dg/reflect/feat2.C: Add also test for __cpp_lib_define_static.
* g++.dg/reflect/feat3.C: New test.
--- libstdc++-v3/include/bits/version.def.jj 2026-01-28 09:34:32.799242560
+0100
+++ libstdc++-v3/include/bits/version.def 2026-02-02 11:56:42.186951034
+0100
@@ -2272,6 +2272,16 @@ ftms = {
};
ftms = {
+ name = define_static;
+ values = {
+ v = 202506;
+ cxxmin = 26;
+ extra_cond = "__cpp_impl_reflection >= 202506L";
+ cxx11abi = yes;
+ };
+};
+
+ftms = {
name = is_implicit_lifetime;
values = {
v = 202302;
--- libstdc++-v3/include/bits/version.h.jj 2026-01-28 09:34:32.799242560
+0100
+++ libstdc++-v3/include/bits/version.h 2026-02-02 11:56:49.231954047 +0100
@@ -2546,6 +2546,16 @@
#endif /* !defined(__cpp_lib_reflection) */
#undef __glibcxx_want_reflection
+#if !defined(__cpp_lib_define_static)
+# if (__cplusplus > 202302L) && _GLIBCXX_USE_CXX11_ABI &&
(__cpp_impl_reflection >= 202506L)
+# define __glibcxx_define_static 202506L
+# if defined(__glibcxx_want_all) || defined(__glibcxx_want_define_static)
+# define __cpp_lib_define_static 202506L
+# endif
+# endif
+#endif /* !defined(__cpp_lib_define_static) */
+#undef __glibcxx_want_define_static
+
#if !defined(__cpp_lib_is_implicit_lifetime)
# if (__cplusplus >= 202100L) &&
(__has_builtin(__builtin_is_implicit_lifetime))
# define __glibcxx_is_implicit_lifetime 202302L
--- libstdc++-v3/include/std/meta.jj 2026-01-15 16:33:47.022097704 +0100
+++ libstdc++-v3/include/std/meta 2026-02-02 11:57:24.436237366 +0100
@@ -34,6 +34,7 @@
#endif
#define __glibcxx_want_reflection
+#define __glibcxx_want_define_static
#include <bits/version.h>
#if __glibcxx_reflection >= 202506L // C++ >= 26 && __cpp_impl_reflection
--- gcc/testsuite/g++.dg/reflect/feat2.C.jj 2026-01-15 16:33:47.008097942
+0100
+++ gcc/testsuite/g++.dg/reflect/feat2.C 2026-02-02 11:58:52.250754011
+0100
@@ -9,3 +9,9 @@
#elif __cpp_lib_reflection != 202506
# error "__cpp_lib_reflection != 202506"
#endif
+
+#ifndef __cpp_lib_define_static
+# error "__cpp_lib_define_static"
+#elif __cpp_lib_define_static != 202506
+# error "__cpp_lib_define_static != 202506"
+#endif
--- gcc/testsuite/g++.dg/reflect/feat3.C.jj 2026-02-02 11:58:59.463632171
+0100
+++ gcc/testsuite/g++.dg/reflect/feat3.C 2026-02-02 11:59:07.636494114
+0100
@@ -0,0 +1,17 @@
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+// Test feature test macros.
+
+#include <meta>
+
+#ifndef __cpp_lib_reflection
+# error "__cpp_lib_reflection"
+#elif __cpp_lib_reflection != 202506
+# error "__cpp_lib_reflection != 202506"
+#endif
+
+#ifndef __cpp_lib_define_static
+# error "__cpp_lib_define_static"
+#elif __cpp_lib_define_static != 202506
+# error "__cpp_lib_define_static != 202506"
+#endif
Jakub
