NAME

atomic_exchange, atomic_exchange_explicit — atomically exchange the value of an object

SYNOPSIS

#include <stdatomic.h>

C atomic_exchange(volatile A *object, C desired);
C atomic_exchange_explicit(volatile A *object, C desired,
       memory_order order);


DESCRIPTION

^[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2024 defers to the ISO C standard.

Implementations that define the macro __STDC_NO_ATOMICS__ need not provide the <stdatomic.h> header nor support these generic functions.

The atomic_exchange_explicit() generic function shall atomically replace the value pointed to by object with desired. This operation shall be an atomic read-modify-write operation (see XBD 4.15.1 Memory Ordering). Memory shall be affected according to the value of order.

The atomic_exchange() generic function shall be equivalent to atomic_exchange_explicit() called with order set to memory_order_seq_cst.

RETURN VALUE

These generic functions shall return the value pointed to by object immediately before the effects.

ERRORS

No errors are defined.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

XBD 4.15.1 Memory Ordering, <stdatomic.h>

CHANGE HISTORY

First released in Issue 8. Included for alignment with the ISO/IEC 9899:2018 standard.