[#ASYNC_set_mem_functions]
= ASYNC_set_mem_functions
:mrdocs:

Install custom stack allocators used for ASYNC jobs on POSIX.

== Synopsis

Declared in `<openssl/async.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
ASYNC_set_mem_functions(
    xref:ASYNC_stack_alloc_fn.adoc[ASYNC_stack_alloc_fn] alloc_fn,
    xref:ASYNC_stack_free_fn.adoc[ASYNC_stack_free_fn] free_fn);
----

== Description

Must be called before any asynchronous job allocates a stack. On unsupported platforms the call fails and the defaults remain in effect.

== Return Value

1 if custom allocators are supported and none have been used yet, or 0 otherwise.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *alloc_fn*
| Allocator called when OpenSSL needs a job stack, or NULL for the default.
| *free_fn*
| Matching free callback for stacks returned by `alloc_fn,` or NULL for the default.
|===


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