C++ attribute: deprecated (since C++14)
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Indicates that the name or entity declared with this attribute is deprecated, that is, the use is allowed, but discouraged for some reason.
Contents
[edit] 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
[edit] 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 };,
- 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.
[edit] 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.[edit] References
- C++23 standard (ISO/IEC 14882:2024):
- 9.12.5 Deprecated attribute [dcl.attr.deprecated]
- C++20 standard (ISO/IEC 14882:2020):
- 9.12.4 Deprecated attribute [dcl.attr.deprecated]
- C++17 standard (ISO/IEC 14882:2017):
- 10.6.4 Deprecated attribute [dcl.attr.deprecated]
- C++14 standard (ISO/IEC 14882:2014):
- 7.6.5 Deprecated attribute [dcl.attr.deprecated]
[edit] See also
C documentation for deprecated