Difference between revisions of "cpp/language/attributes/deprecated"

Latest revision as of 11:41, 12 August 2024

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

[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 {};,

• 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 <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();
}

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

[edit] See also