From: Jakub Jelinek <jakub@redhat.com>
Date: Tue, 3 Feb 2026 13:22:46 +0000 (+0100)
Subject: libstdc++: Define __cpp_lib_define_static [PR123921]
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4a514ea759f6045ef091504f2afcf4b618fe2639;p=thirdparty%2Fgcc.git

libstdc++: Define __cpp_lib_define_static [PR123921]

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.

2026-02-03  Jakub Jelinek  <jakub@redhat.com>

	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.
---

diff --git a/gcc/testsuite/g++.dg/reflect/feat2.C b/gcc/testsuite/g++.dg/reflect/feat2.C
index 902732b0824..dc4c82cdaab 100644
--- a/gcc/testsuite/g++.dg/reflect/feat2.C
+++ b/gcc/testsuite/g++.dg/reflect/feat2.C
@@ -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
diff --git a/gcc/testsuite/g++.dg/reflect/feat3.C b/gcc/testsuite/g++.dg/reflect/feat3.C
new file mode 100644
index 00000000000..68b72e27f39
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/feat3.C
@@ -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
diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def
index 8c5f4bb7c4c..ba0ef5aecfd 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -2271,6 +2271,16 @@ ftms = {
   };
 };
 
+ftms = {
+  name = define_static;
+  values = {
+    v = 202506;
+    cxxmin = 26;
+    extra_cond = "__cpp_impl_reflection >= 202506L";
+    cxx11abi = yes;
+  };
+};
+
 ftms = {
   name = is_implicit_lifetime;
   values = {
diff --git a/libstdc++-v3/include/bits/version.h b/libstdc++-v3/include/bits/version.h
index 985701447be..74d1a28f75c 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -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
diff --git a/libstdc++-v3/include/std/meta b/libstdc++-v3/include/std/meta
index 033746a4034..59a678037a1 100644
--- a/libstdc++-v3/include/std/meta
+++ b/libstdc++-v3/include/std/meta
@@ -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