3 files changed, 38 insertions, 0 deletions

diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def
index 1118da4..f60a518 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -1951,6 +1951,15 @@ ftms = {
 };
 
 ftms = {
+  name = observable_checkpoint;
+  values = {
+    v = 202506;
+    cxxmin = 26;
+    extra_cond = "__has_builtin(__builtin_observable_checkpoint)";
+  };
+};
+
+ftms = {
   name = algorithm_default_value_type;
   values = {
     v = 202403;
diff --git a/libstdc++-v3/include/bits/version.h b/libstdc++-v3/include/bits/version.h
index c452bbe..cbd82ff 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -2181,6 +2181,16 @@
 #endif /* !defined(__cpp_lib_unreachable) */
 #undef __glibcxx_want_unreachable
 
+#if !defined(__cpp_lib_observable_checkpoint)
+# if (__cplusplus >  202302L) && (__has_builtin(__builtin_observable_checkpoint))
+#  define __glibcxx_observable_checkpoint 202506L
+#  if defined(__glibcxx_want_all) || defined(__glibcxx_want_observable_checkpoint)
+#   define __cpp_lib_observable_checkpoint 202506L
+#  endif
+# endif
+#endif /* !defined(__cpp_lib_observable_checkpoint) && defined(__glibcxx_want_observable_checkpoint) */
+#undef __glibcxx_want_observable_checkpoint
+
 #if !defined(__cpp_lib_algorithm_default_value_type)
 # if (__cplusplus >  202302L)
 #  define __glibcxx_algorithm_default_value_type 202403L
diff --git a/libstdc++-v3/include/std/utility b/libstdc++-v3/include/std/utility
index 8a85ccf..3ae1852 100644
--- a/libstdc++-v3/include/std/utility
+++ b/libstdc++-v3/include/std/utility
@@ -98,6 +98,7 @@
 #define __glibcxx_want_tuple_element_t
 #define __glibcxx_want_tuples_by_type
 #define __glibcxx_want_unreachable
+#define __glibcxx_want_observable_checkpoint
 #define __glibcxx_want_tuple_like
 #define __glibcxx_want_constrained_equality
 #include <bits/version.h>
@@ -234,6 +235,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   }
 #endif
 
+
+#ifdef __cpp_lib_observable_checkpoint // C++ >= 26
+  /// Informs the compiler that prior actions are considered observable.
+  /**
+   * This may be used to limit the extent to which optimisations based on the
+   * assumed unreachability of undefined behaviour can propagate to earlier
+   * code.
+   *
+   * @since C++26
+   */
+  [[__gnu__::__always_inline__]]
+  inline void
+  observable_checkpoint() noexcept
+  {
+    return __builtin_observable_checkpoint();
+  }
+#endif
+
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace