[#BN_GENCB_set]
= BN_GENCB_set
:mrdocs:

Populate a BN_GENCB with a new‐style progress callback that returns success/failure.

== Synopsis

Declared in `<openssl/bn.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
void
BN_GENCB_set(
    xref:BN_GENCB.adoc[BN_GENCB]* gencb,
    int(* callback)(int, int, xref:BN_GENCB.adoc[BN_GENCB]*),
    void* cb_arg);
----

== Parameters

[cols="1,4"]
|===
| Name| Description
| *gencb*
| Callback object from BN_GENCB_new() (or a stack instance where supported).
| *callback*
| Callback receiving (event, progress, `gencb);` should return 1 on success or 0 on error.
| *cb_arg*
| Opaque pointer stored in `gencb` and retrievable via BN_GENCB_get_arg().
|===


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