Merge 2025-06 LWG Motion 8

P3641R0 Rename std::observable to std::observable_checkpoint

Author: tkoeppe

source/intro.tex

@@ -962,7 +962,7 @@
 Certain events in the execution of a program
 are termed \defnadj{observable}{checkpoints}.
 \begin{note}
-A call to \tcode{std::observable}\iref{utility.undefined}
+A call to \tcode{std::observable_checkpoint}\iref{utility.undefined}
 is an observable checkpoint,
 as are certain parts of
 the evaluation of contract assertions\iref{basic.contract}.

source/support.tex

@@ -765,6 +765,7 @@
   // \libheader{string}, \libheader{unordered_map}, \libheader{unordered_set}, \libheader{vector}
 #define @\defnlibxname{cpp_lib_not_fn}@                            202306L // freestanding, also in \libheader{functional}
 #define @\defnlibxname{cpp_lib_null_iterators}@                    201304L // freestanding, also in \libheader{iterator}
+#define @\defnlibxname{cpp_lib_observable_checkpoint}@             202506L // freestanding, also in \libheader{utility}
 #define @\defnlibxname{cpp_lib_optional}@                          202506L // also in \libheader{optional}
 #define @\defnlibxname{cpp_lib_optional_range_support}@            202406L // freestanding, also in \libheader{optional}
 #define @\defnlibxname{cpp_lib_out_ptr}@                           202311L // freestanding, also in \libheader{memory}

source/utilities.tex

@@ -95,7 +95,7 @@
 
   // \ref{utility.undefined}, undefined behavior
   [[noreturn]] void unreachable();
-  void observable() noexcept;
+  void observable_checkpoint() noexcept;
 
   // \ref{intseq}, compile-time integer sequences%
 \indexlibraryglobal{index_sequence}%
@@ -720,9 +720,9 @@
 \end{example}
 \end{itemdescr}
 
-\indexlibraryglobal{observable}%
+\indexlibraryglobal{observable_checkpoint}%
 \begin{itemdecl}
-void observable() noexcept;
+void observable_checkpoint() noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}