[#CRYPTO_atomic_add]
= CRYPTO_atomic_add
:mrdocs:

Atomically add `amount` to *`val,` optionally under `lock.`

== Synopsis

Declared in `<openssl/crypto.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
CRYPTO_atomic_add(
    int* val,
    int amount,
    int* ret,
    xref:CRYPTO_RWLOCK.adoc[CRYPTO_RWLOCK]* lock);
----

== Return Value

1 on success, or 0 on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *val*
| Integer to modify in place.
| *amount*
| Value added to *`val.`
| *ret*
| Receives the post‐add value of *`val;` must not be NULL.
| *lock*
| Optional CRYPTO_RWLOCK used when hardware atomics are unavailable, or NULL.
|===


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