Suppresses warnings on unused entities.

[edit]Syntax

[edit]Explanation

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

• struct/union:struct[[maybe_unused]] S;,
• typedef name:[[maybe_unused]]typedef S* PS;,
• object:[[maybe_unused]]int x;,
• struct/union member:union U{[[maybe_unused]]int n;};,
• function:[[maybe_unused]]void f(void);,
• enumeration:enum[[maybe_unused]] E{};,
• enumerator:enum{ A[[maybe_unused]], B[[maybe_unused]]=42};.

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

[edit]Example

#include <assert.h> [[maybe_unused]]void f([[maybe_unused]] _Bool cond1,[[maybe_unused]] _Bool cond2){[[maybe_unused]] _Bool b= cond1&& cond2;assert(b);// in release mode, assert is compiled out, and b is unused// no warning because it is declared [[maybe_unused]]}// parameters cond1 and cond2 are not used, no warning int main(void){    f(1,1);}

[edit]See also

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