cppdraft_translate/cppdraft/class/static.md

[class.static]

# 11 Classes [[class]](./#class)

## 11.4 Class members [[class.mem]](class.mem#class.static)

### 11.4.9 Static members [class.static]

#### [11.4.9.1](#general) General [[class.static.general]](class.static.general)

[1](#general-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/classes.tex#L2732)

A static member s of class X may be referred to
using the [*qualified-id*](expr.prim.id.qual#nt:qualified-id "7.5.5.3 Qualified names [expr.prim.id.qual]") expression X​::​s; it is not
necessary to use the class member access syntax ([[expr.ref]](expr.ref "7.6.1.5 Class member access")) to
refer to a static member[.](#general-1.sentence-1)

A static member may be
referred to using the class member access syntax, in which case the
object expression is evaluated[.](#general-1.sentence-2)

[*Example [1](#general-example-1)*: struct process {static void reschedule();};
process& g();

void f() { process::reschedule(); // OK, no object necessary g().reschedule(); // g() is called} — *end example*]

[2](#general-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/classes.tex#L2753)

Static members obey the usual class member access rules ([[class.access]](class.access "11.8 Member access control"))[.](#general-2.sentence-1)

When used in the declaration of a class
member, the static specifier shall only be used in the member
declarations that appear within the [*member-specification*](class.mem.general#nt:member-specification "11.4.1 General [class.mem.general]") of
the class definition[.](#general-2.sentence-2)

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

It cannot be specified in member declarations that appear in namespace scope[.](#general-2.sentence-3)

— *end note*]

#### [11.4.9.2](#mfct) Static member functions [[class.static.mfct]](class.static.mfct)

[1](#mfct-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/classes.tex#L2766)

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

The rules described in [[class.mfct]](class.mfct "11.4.2 Member functions") apply to static member
functions[.](#mfct-1.sentence-1)

— *end note*]

[2](#mfct-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/classes.tex#L2772)

[*Note [2](#mfct-note-2)*:

A static member function does not have a this pointer ([[expr.prim.this]](expr.prim.this "7.5.3 This"))[.](#mfct-2.sentence-1)

A static member function cannot be qualified with const,volatile, or virtual ([[dcl.fct]](dcl.fct "9.3.4.6 Functions"))[.](#mfct-2.sentence-2)

— *end note*]

#### [11.4.9.3](#data) Static data members [[class.static.data]](class.static.data)

[1](#data-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/classes.tex#L2783)

A static data member is not part of the subobjects of a class[.](#data-1.sentence-1)

If a
static data member is declared thread_local there is one copy of
the member per thread[.](#data-1.sentence-2)

If a static data member is not declaredthread_local there is one copy of the data member that is shared by all
the objects of the class[.](#data-1.sentence-3)

[2](#data-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/classes.tex#L2790)

A static data member shall not be mutable ([[dcl.stc]](dcl.stc "9.2.2 Storage class specifiers"))[.](#data-2.sentence-1)

A static data member shall not be a direct member ([[class.mem]](class.mem "11.4 Class members"))
of an unnamed ([[class.pre]](class.pre "11.1 Preamble")) or local ([[class.local]](class.local "11.6 Local class declarations")) class or
of a (possibly indirectly) nested class ([[class.nest]](class.nest "11.4.12 Nested class declarations")) thereof[.](#data-2.sentence-2)

[3](#data-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/classes.tex#L2796)

The declaration of a non-inline
static data member in its class definition
is not a definition and may be of an incomplete type other thancv void[.](#data-3.sentence-1)

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

The [*initializer*](dcl.init.general#nt:initializer "9.5.1 General [dcl.init.general]") in the definition of a
static data member is in the scope of its
class ([[basic.scope.class]](basic.scope.class "6.4.7 Class scope"))[.](#data-3.sentence-2)

— *end note*]

[*Example [1](#data-example-1)*: class process {static process* run_chain; static process* running;};

process* process::running = get_main();
process* process::run_chain = running;

The definition of the static data member run_chain of classprocess inhabits the global scope; the notationprocess​::​run_chain indicates that the member run_chain is a member of class process and in the scope of classprocess[.](#data-3.sentence-3)

In the static data member definition, the[*initializer*](dcl.init.general#nt:initializer "9.5.1 General [dcl.init.general]") expression refers to the static data
member running of class process[.](#data-3.sentence-4)

— *end example*]

[*Note [2](#data-note-2)*:

Once the static data member has been defined, it exists even if
no objects of its class have been created[.](#data-3.sentence-5)

[*Example [2](#data-example-2)*:

In the example above, run_chain and running exist even
if no objects of class process are created by the program[.](#data-3.sentence-6)

— *end example*]

The initialization and destruction of static data members is described in[[basic.start.static]](basic.start.static "6.10.3.2 Static initialization"), [[basic.start.dynamic]](basic.start.dynamic "6.10.3.3 Dynamic initialization of non-block variables"), and [[basic.start.term]](basic.start.term "6.10.3.4 Termination")[.](#data-3.sentence-7)

— *end note*]

[4](#data-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/classes.tex#L2840)

If a non-volatile non-inline const static data member is
of integral or enumeration type,
its declaration in the class definition can specify a[*brace-or-equal-initializer*](dcl.init.general#nt:brace-or-equal-initializer "9.5.1 General [dcl.init.general]") in which every[*initializer-clause*](dcl.init.general#nt:initializer-clause "9.5.1 General [dcl.init.general]") that is an [*assignment-expression*](expr.assign#nt:assignment-expression "7.6.19 Assignment and compound assignment operators [expr.assign]") is a constant expression ([[expr.const]](expr.const "7.7 Constant expressions"))[.](#data-4.sentence-1)

The member shall still be defined in a namespace scope if
it is odr-used ([[basic.def.odr]](basic.def.odr#term.odr.use "6.3 One-definition rule")) in the program and the
namespace scope definition shall not contain an [*initializer*](dcl.init.general#nt:initializer "9.5.1 General [dcl.init.general]")[.](#data-4.sentence-2)

The declaration of an inline static data member (which is a definition)
may specify a [*brace-or-equal-initializer*](dcl.init.general#nt:brace-or-equal-initializer "9.5.1 General [dcl.init.general]")[.](#data-4.sentence-3)

If the
member is declared with the constexpr specifier, it may be
redeclared in namespace scope with no initializer (this usage is
deprecated; see [[depr.static.constexpr]](depr.static.constexpr "D.7 Redeclaration of static constexpr data members"))[.](#data-4.sentence-4)

Declarations of other
static data members shall not specify a [*brace-or-equal-initializer*](dcl.init.general#nt:brace-or-equal-initializer "9.5.1 General [dcl.init.general]")[.](#data-4.sentence-5)

[5](#data-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/classes.tex#L2857)

[*Note [3](#data-note-3)*:

There is exactly one definition of a static data member
that is odr-used ([[basic.def.odr]](basic.def.odr#term.odr.use "6.3 One-definition rule")) in a valid program[.](#data-5.sentence-1)

— *end note*]

[6](#data-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/classes.tex#L2863)

[*Note [4](#data-note-4)*:

Static data members of a class in namespace scope have the linkage of the name of the class ([[basic.link]](basic.link "6.7 Program and linkage"))[.](#data-6.sentence-1)

— *end note*]