NAME

atomic_is_lock_free — indicate whether or not atomic operations are lock-free

SYNOPSIS

#include <stdatomic.h>

_Bool atomic_is_lock_free(const volatile A *obj);


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_is_lock_free() generic function shall indicate whether or not atomic operations on objects of the type pointed to by obj are lock-free; obj can be a null pointer.

RETURN VALUE

The atomic_is_lock_free() generic function shall return a non-zero value if and only if atomic operations on objects of the type pointed to by obj are lock-free. During the lifetime of the calling process, the result of the lock-free query shall be consistent for all pointers of the same type.

ERRORS

No errors are defined.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

Operations that are lock-free should also be address-free. That is, atomic operations on the same memory location via two different addresses will communicate atomically. The implementation should not depend on any per-process state. This restriction enables communication via memory mapped into a process more than once and memory shared between two processes.

FUTURE DIRECTIONS

None.

SEE ALSO

XBD <stdatomic.h>

CHANGE HISTORY

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