C++ attribute: deprecated (since C++14) (original) (raw)
Indicates that the name or entity declared with this attribute is deprecated, that is, the use is allowed, but discouraged for some reason.
[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 };, | (since C++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.
[edit] Example
#include [[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]