Difference between revisions of "cpp/language/attributes/deprecated"
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< cpp | language | attributes
(Added an example.) |
(Example enlargement)) |
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===Example=== | ===Example=== | ||
{{example | {{example | ||
| − | |code=[[deprecated("Use calcSomethingDifferently(int).")]] | + | |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) { | int calcSomething(int x) { | ||
return x * 2; | return x * 2; | ||
} | } | ||
| + | |||
| + | int main() | ||
| + | { | ||
| + | TriassicPeriod(); | ||
| + | JurassicPeriod(); | ||
| + | } | ||
| + | | p=true | ||
| + | | 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. | ||
}} | }} | ||
{{langlinks|ja|zh}} | {{langlinks|ja|zh}} | ||
Revision as of 20:31, 24 June 2020
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 | - | text 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: struct [[deprecated]] S;,
- typedef-name, including those declared by alias declaration: [[deprecated]] typedef S* PS;, using PS [[deprecated]] = S*;,
- variable, including static data member: [[deprecated]] int x;,
- non-static data member: union U { [[deprecated]] int n; };,
- function: [[deprecated]] void f();,
- namespace: namespace [[deprecated]] NS { int x; }
- enumeration: enum [[deprecated]] E {};,
- enumerator: enum { A [[deprecated]], B [[deprecated]] = 42 };.
- template specialization: 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.
