함수 앞에 [[deprecated]]를 붙이거나 변수 선언 앞에 __attribute__((deprecated))를 붙이면 컴파일 시에 경고를 출력한다.

경고 메시지를 직접 지정하는 방법도 있다.

아래 예제를 참고할 것

#include <iostream>

using namespace std;

[[deprecated]]
void test1(void)
{

}

[[deprecated("replaced by ...")]]
void test2(void)
{

}

int main(void)
{
    __attribute__((deprecated)) int a = 3;
    __attribute__((deprecated("deprecated for ..."))) int b = 4;

    cout << a << endl;
    cout << b << endl;

    test1();
    test2();

    return 0;
}

deprecated_attribute.cc: In function ‘int main()’:
deprecated_attribute.cc:22:13: warning: ‘a’ is deprecated -Wdeprecated-declarations
22 | cout << a << endl;
| ^
deprecated_attribute.cc:19:37: note: declared here
19 | attribute((deprecated)) int a = 3;
| ^
deprecated_attribute.cc:23:13: warning: ‘b’ is deprecated: deprecated for ... -Wdeprecated-declarations
23 | cout << b << endl;
| ^
deprecated_attribute.cc:20:59: note: declared here
20 | attribute((deprecated("deprecated for ..."))) int b = 4;
| ^
deprecated_attribute.cc:25:11: warning: ‘void test1()’ is deprecated -Wdeprecated-declarations
25 | test1();
| ^
deprecated_attribute.cc:6:6: note: declared here
6 | void test1(void)
| ^~~~~
deprecated_attribute.cc:25:11: warning: ‘void test1()’ is deprecated -Wdeprecated-declarations
25 | test1();
| ^
deprecated_attribute.cc:6:6: note: declared here
6 | void test1(void)
| ^~~~~
deprecated_attribute.cc:26:11: warning: ‘void test2()’ is deprecated: replaced by ... -Wdeprecated-declarations
26 | test2();
| ^
deprecated_attribute.cc:12:6: note: declared here
12 | void test2(void)
| ^~~~~
deprecated_attribute.cc:26:11: warning: ‘void test2()’ is deprecated: replaced by ... -Wdeprecated-declarations
26 | test2();
| ^
deprecated_attribute.cc:12:6: note: declared here
12 | void test2(void)
| ^~~~~

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