[#BN_GENCB_set_old]
= BN_GENCB_set_old
:mrdocs:

Populate a BN_GENCB with a legacy void‐returning progress callback.

== Synopsis

Declared in `<openssl/bn.h>`

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

== Parameters

[cols="1,4"]
|===
| Name| Description
| *gencb*
| Callback object from BN_GENCB_new() (or a stack instance).
| *callback*
| Old‐style callback receiving (event, progress, `cb_arg).`
| *cb_arg*
| Opaque pointer passed through to `callback.`
|===


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