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C++ attribute: maybe_unused (since C++17)

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Attributes
(C++14)
(C++17)
maybe_unused
(C++17)
(C++20)(C++20)
 

Suppresses warnings on unused entities.

Contents

[edit] Syntax

[[maybe_unused]]

[edit] Explanation

This attribute can appear in the declaration of the following entities:

If the compiler issues warnings on unused entities, that warning is suppressed for any entity declared maybe_unused.

[edit] Example

#include <cassert>
 
[[maybe_unused]] void f([[maybe_unused]] bool thing1,
                        [[maybe_unused]] bool thing2)
{
   [[maybe_unused]] bool b = thing1 && thing2;
   assert(b); // in release mode, assert is compiled out, and b is unused
              // no warning because it is declared [[maybe_unused]]
} // parameters thing1 and thing2 are not used, no warning
 
int main() {;}

[edit] See also

C documentation for maybe_unused