fixup: add 34.8

Author: jensmaurer

source/exec.tex

@@ -1094,6 +1094,57 @@
 
 \rSec1[exec.opstate]{Operation states}
 
+\rSec2[exec.opstate.general]{General}
+
+\pnum
+The \libconcept{operation_state} concept defines
+the requirements of an operation state type\iref{async.ops}.
+\begin{codeblock}
+namespace std::execution {
+  template<class O>
+    concept @\deflibconcept{operation_state}@ =
+      @\libconcept{derived_from}@<typename O::operation_state_concept, operation_state_t> &&
+      is_object_v<O> &&
+      requires (O& o) {
+        { start(o) } noexcept;
+      };
+}
+\end{codeblock}
+
+\pnum
+If an \libconcept{operation_state} object is destroyed
+during the lifetime of its asynchronous operation\iref{async.ops},
+the behavior is undefined.
+\begin{note}
+The \libconcept{operation_state} concept does not impose requirements
+on any operations other than destruction and \tcode{start},
+including copy and move operations.
+Invoking any such operation on an object
+whose type models \libconcept{operation_state} can lead to undefined behavior.
+\end{note}
+
+\pnum
+The program is ill-formed
+if it performs a copy or move construction or assigment operation on
+an operation state object created by connecting a library-provided sender.
+
+\rSec2[exec.opstate.start]{\tcode{execution::start}}
+
+\pnum
+The name \tcode{start} denotes a customization point object
+that starts\iref{async.ops}
+the asynchronous operation associated with the operation state object.
+For a subexpression \tcode{op},
+the expression \tcode{start(op)} is ill-formed
+if \tcode{op} is an rvalue.
+Otherwise, it is expression-equivalent to
+\tcode{\exposid{MANDATE-NOTHROW}(op.start())}.
+
+\pnum
+If \tcode{op.start()} does not start\iref{async.ops}
+the asynchronous operation associated with the operation state \tcode{op},
+the behavior of calling \tcode{start(op)} is undefined.
+
 \rSec1[exec.snd]{Senders}
 
 \rSec1[exec.util]{Sender/receiver utilities}