Updated: April 19, 2023 |
Atomically add to the value of an atomic object (C11)
#include <stdatomic.h> C atomic_fetch_add( volatile A *obj, M amount ); C atomic_fetch_add_explicit( volatile A *obj, M amount, memory_order order );
The atomic_fetch_add() and atomic_fetch_add_explicit() functions are generic functions that atomically add the given value to the given atomic object. The atomic_fetch_add() function orders memory access according to memory_order_seq_cst; atomic_fetch_add_explicit() orders them as specified by order.
The implementation of atomic functions may depend on the architecture. For more information, see LL/SC vs LSE atomic operations in the description in Building Embedded Systems of the cpuinfo area of the system page.
The previous value of the atomic object. The C represents the non-atomic data type that corresponds to the atomic object.
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | Read the Caveats |
Signal handler | Read the Caveats |
Thread | Yes |
If this function is lock-free (see atomic_is_lock_free()), it's safe to call it from an ISR or signal handler.