Attributes

cppreference

[[nodiscard]]/[[nodiscar("reason...")]] (CPP17)

If a function declared nodiscard or returning an enumeration or class declared nodiscard is called without the return value being used, other than a cast to void, the compiler is encouraged to issue a warning.

Appears in a function, enumeration, or class declaration.

[[maybe_unused]] (CPP17)

Suppresses warnings on unused entities.

[[fallthrough]] (CPP17)

Indicates that the fall-through from the previous case label is intentional and should not be diagnosed by a compiler that warns on fall-through.

[[likely]] / [[unlikely]] (CPP20)

video resource

[[no_unique_address]] (CPP20)

no_unique_address

[[assume(expression)]] (CPP23)

assume

[[noreturn]] (CPP11)

Indicates that the function will not return control flow to the calling function after it finishes (e.g. functions that terminate the application, throw exceptions, loop indefinitely, etc.).

[[noreturn]] void f()
{
    throw "error";
    // OK
}
 
void q [[noreturn]] (int i)
{
    // behavior is undefined if called with an argument <= 0
    if (i > 0)
        throw "positive";
}
 
// void h() [[noreturn]]; // error: attribute applied to function type of h, not h itself
 
int main()
{
    try { f(); } catch(...) {}
    try { q(42); } catch(...) {}
}

[[deprecated]]/[[deprecated("reason")]] (CPP14)

Mark something as deprecated, and optionally provide a reason.

[[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";
}