[#BIO_debug_callback]
= BIO_debug_callback
:mrdocs:

Default legacy BIO debug logger writing to the BIO's callback‐argument BIO (deprecated).

== Synopsis

Declared in `<openssl/bio.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[deprecated]]
long
BIO_debug_callback(
    xref:BIO.adoc[BIO]* bio,
    int cmd,
    char const* argp,
    int argi,
    long argl,
    long ret);
----

[WARNING]
====
https://en.cppreference.com/cpp/language/attributes/deprecated[Deprecated^]. Use of this entity is allowed but discouraged.
====
== Return Value

`ret` unchanged (pass‐through debug callback).

== Parameters

[cols="1,4"]
|===
| Name| Description
| *bio*
| BIO whose operation is being reported.
| *cmd*
| BIO_CB_* operation code (read, write, ctrl, …).
| *argp*
| Pointer argument for the operation (buffer or ctrl pointer), or NULL.
| *argi*
| Integer argument for ctrl‐style operations.
| *argl*
| Long argument for ctrl‐style operations.
| *ret*
| Return value being reported for the operation.
|===


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