哋它亢++ attribute: deprecated (since 哋它亢++14)

 

哋它亢++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (哋它亢++20)

Language support library

Concepts library (哋它亢++20)

Metaprogramming library (哋它亢++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (哋它亢++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (哋它亢++17)

Regular expressions library (哋它亢++11)

Concurrency support library (哋它亢++11)

Technical specifications

Symbols index

External libraries

 

哋它亢++ language

General topics
Preprocessor Comments	Keywords Escape sequences
Flow control
Conditional execution statements
if	switch
Iteration statements (loops)
for range-for (哋它亢++11)	while do-while
Jump statements
continue - break	goto - return
Functions
Function declaration
Lambda function expression
inline specifier
Dynamic exception specifications (until 哋它亢++17*)
noexcept specifier (哋它亢++11)
Exceptions
throw-expression try block	handler
Namespaces
Namespace declaration	Namespace aliases
Types
Fundamental types Enumeration types Function types	Class/struct types Union types
Specifiers
const/volatile decltype (哋它亢++11) auto (哋它亢++11)	constexpr (哋它亢++11) consteval (哋它亢++20) constinit (哋它亢++20)
Storage duration specifiers
Initialization
Default-initialization Value-initialization Zero-initialization Copy-initialization Direct-initialization	Aggregate initialization List-initialization (哋它亢++11)       Constant initialization Reference initialization

Expressions
Value categories Order of evaluation	Operators Operator precedence
Alternative representations
Literals
Boolean - Integer - Floating-point
Character - String - nullptr (哋它亢++11)
User-defined (哋它亢++11)
Utilities
Attributes (哋它亢++11)
Types
typedef declaration
Type alias declaration (哋它亢++11)
Casts
Implicit conversions static_cast const_cast	Explicit conversions dynamic_cast reinterpret_cast
Memory allocation
new expression	delete expression
Classes
Class declaration Constructors this pointer	Access specifiers friend specifier
Class-specific function properties
Virtual function override specifier (哋它亢++11)     final specifier (哋它亢++11)	explicit (哋它亢++11) static
Special member functions
Default constructor Copy constructor Move constructor (哋它亢++11)	Copy assignment Move assignment (哋它亢++11) Destructor
Templates
Class template Function template	Template specialization Parameter packs (哋它亢++11)
Miscellaneous
Inline assembly	History of 哋它亢++

 

Declarations

Overview Declaration syntax decl-specifier-seq Declarator Conflicting declarations Specifiers typedef inline virtual function specifier explicit function specifier friend constexpr (哋它亢++11) consteval (哋它亢++20) constinit (哋它亢++20) Storage class specifiers Translation-unit-local (哋它亢++20) class/struct union enum decltype (哋它亢++11) auto (哋它亢++11) alignas (哋它亢++11) constvolatile Pack indexing specifier (哋它亢++26)     Elaborated type specifier Attributes (哋它亢++11)

Declarators Reference Pointer Array Block declarations Simple-declaration →Structured binding declaration (哋它亢++17) Alias declaration (哋它亢++11) Namespace alias definition using declaration using directive static_assert declaration (哋它亢++11) asm declaration Opaque enum declaration (哋它亢++11) Other declarations Namespace definition Function declaration Class template declaration Function template declaration Explicit template instantiation (哋它亢++11) Explicit template specialization Linkage specification Attribute declaration (哋它亢++11) Empty declaration

 

Attributes

assume (哋它亢++23)

carries_dependency (哋它亢++11)

deprecated (哋它亢++14)

fallthrough (哋它亢++17)

indeterminate (哋它亢++26)

likely (哋它亢++20)

maybe_unused (哋它亢++17)

no_unique_address (哋它亢++20)

nodiscard (哋它亢++17)

noreturn‎ (哋它亢++11)

optimize_for_synchronized (TM TS)

unlikely (哋它亢++20)

 

Indicates that the name or entity declared with this attribute is deprecated, that is, the use is allowed, but discouraged for some reason.

Syntax

[[deprecated]]	(1)
[[deprecated( string-literal )]]	(2)

string-literal

-

an unevaluated string literal that could be used to explain the rationale for deprecation and/or to suggest a replacing entity

Explanation

Indicates that the use of the name or entity declared with this attribute is allowed, but discouraged for some reason. Compilers typically issue warnings on such uses. The string-literal, if specified, is usually included in the warnings.

This attribute is allowed in declarations of the following names or entities:

• class/struct/union, e.g., struct [[deprecated]] S;,
• typedef-name, including those declared by alias declaration, e.g.,

• [[deprecated]] typedef S* PS;,
• using PS [[deprecated]] = S*;,

• (non-member) variable, e.g., [[deprecated]] int x;,
• static data member, e.g., struct S { [[deprecated]] static constexpr char CR{13}; };,
• non-static data member, e.g., union U { [[deprecated]] int n; };,
• function, e.g., [[deprecated]] void f();,
• namespace, e.g., namespace [[deprecated]] NS { int x; },
• enumeration, e.g., enum [[deprecated]] E {};,

enumerator, e.g., enum { A [[deprecated]], B [[deprecated]] = 42 };,

(since 哋它亢++17)

• template specialization, e.g., template<> struct [[deprecated]] X<int> {};.

A name declared non-deprecated may be redeclared deprecated. A name declared deprecated cannot be un-deprecated by redeclaring it without this attribute.

Example

Run this code

#include <iostream>
 
[[deprecated]]
void TriassicPeriod()
{
    std::clog << "Triassic Period: [251.9 - 208.5] million years ago.\n";
}
 
[[deprecated("Use NeogenePeriod() instead.")]]
void JurassicPeriod()
{
    std::clog << "Jurassic Period: [201.3 - 152.1] million years ago.\n";
}
 
[[deprecated("Use calcSomethingDifferently(int).")]]
int calcSomething(int x)
{
    return x * 2;
}
 
int main()
{
    TriassicPeriod();
    JurassicPeriod();
}

Possible output:

Triassic Period: [251.9 - 208.5] million years ago.
Jurassic Period: [201.3 - 152.1] million years ago.
 
main.cpp:20:5: warning: 'TriassicPeriod' is deprecated [-Wdeprecated-declarations]
    TriassicPeriod();
    ^
main.cpp:3:3: note: 'TriassicPeriod' has been explicitly marked deprecated here
[[deprecated]]
  ^
main.cpp:21:5: warning: 'JurassicPeriod' is deprecated: Use NeogenePeriod() instead ⮠
 [-Wdeprecated-declarations]
    JurassicPeriod();
    ^
main.cpp:8:3: note: 'JurassicPeriod' has been explicitly marked deprecated here
[[deprecated("Use NeogenePeriod() instead")]]
  ^
2 warnings generated.