ATOMIC_FLAG_INIT

< cpp‎ | atomic
 
C++
 
Atomic operations library
Types
(C++11)
(C++20)
Functions
(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)
(C++11)
Atomic flags
(C++11)
(C++11)(C++11)
(C++11)(C++11)
Initialization
(C++11)
(C++11)
ATOMIC_FLAG_INIT
(C++11)
Memory ordering
(C++11)
(C++11)
(C++11)
(C++11)
 
Defined in header <atomic>
#define ATOMIC_FLAG_INIT /* implementation-defined */

Defines the expression which can be used to initialize std::atomic_flag to clear (false) state with the statement std::atomic_flag v = ATOMIC_FLAG_INIT;. It is unspecified if it can be used with other initialization contexts.

If the flag has static storage duration, this initialization is static.

This is the only way to initialize std::atomic_flag to a definite value: the value held after any other initialization is unspecified.

Example

Run this code
#include <atomic>
 
std::atomic_flag static_flag = ATOMIC_FLAG_INIT; // static initialization,
// guaranteed to be available during dynamic initialization of static objects.
 
int main()
{
    std::atomic_flag automatic_flag = ATOMIC_FLAG_INIT; // guaranteed to work
//    std::atomic_flag another_flag(ATOMIC_FLAG_INIT); // unspecified
}


See also

(C++11)
 the lock-free boolean atomic type
(class)