[exec.opstate]

# 33 Execution control library [[exec]](./#exec)

## 33.8 Operation states [exec.opstate]

### [33.8.1](#general) General [[exec.opstate.general]](exec.opstate.general)

[1](#general-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/exec.tex#L1273)

The [operation_state](#concept:operation_state "33.8.1 General [exec.opstate.general]") concept defines
the requirements of an operation state type ([[exec.async.ops]](exec.async.ops "33.3 Asynchronous operations"))[.](#general-1.sentence-1)

namespace std::execution {template<class O>concept [operation_state](#concept:operation_state "33.8.1 General [exec.opstate.general]") =[derived_from](concept.derived#concept:derived_from "18.4.3 Concept derived_­from [concept.derived]")<typename O::operation_state_concept, operation_state_t> &&requires (O& o) { start(o); };}

[2](#general-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/exec.tex#L1287)

If an [operation_state](#concept:operation_state "33.8.1 General [exec.opstate.general]") object is destroyed
during the lifetime of its asynchronous operation ([[exec.async.ops]](exec.async.ops "33.3 Asynchronous operations")),
the behavior is undefined[.](#general-2.sentence-1)

[*Note [1](#general-note-1)*:

The [operation_state](#concept:operation_state "33.8.1 General [exec.opstate.general]") concept does not impose requirements
on any operations other than destruction and start,
including copy and move operations[.](#general-2.sentence-2)

Invoking any such operation on an object
whose type models [operation_state](#concept:operation_state "33.8.1 General [exec.opstate.general]") can lead to undefined behavior[.](#general-2.sentence-3)

— *end note*]

[3](#general-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/exec.tex#L1299)

The program is ill-formed
if it performs a copy or move construction or assignment operation on
an operation state object created by connecting a library-provided sender[.](#general-3.sentence-1)

### [33.8.2](#start) execution​::​start [[exec.opstate.start]](exec.opstate.start)

[1](#start-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/exec.tex#L1306)

The name start denotes a customization point object
that starts ([[exec.async.ops]](exec.async.ops "33.3 Asynchronous operations"))
the asynchronous operation associated with the operation state object[.](#start-1.sentence-1)

For a subexpression op,
the expression start(op) is ill-formed
if op is an rvalue[.](#start-1.sentence-2)

Otherwise, it is expression-equivalent to*MANDATE-NOTHROW*(op.start())[.](#start-1.sentence-3)

[2](#start-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/exec.tex#L1316)

If op.start() does not start ([[exec.async.ops]](exec.async.ops "33.3 Asynchronous operations"))
the asynchronous operation associated with the operation state op,
the behavior of calling start(op) is undefined[.](#start-2.sentence-1)