[#CRYPTO_alloc_ex_data]
= CRYPTO_alloc_ex_data
:mrdocs:

Allocate ex_data at index `idx` by invoking the registered new callback if unset.

== Synopsis

Declared in `<openssl/crypto.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
CRYPTO_alloc_ex_data(
    int class_index,
    void* obj,
    xref:CRYPTO_EX_DATA.adoc[CRYPTO_EX_DATA]* ad,
    int idx);
----

== Return Value

1 on success (including when a value is already present), or 0 on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *class_index*
| CRYPTO_EX_INDEX_* identifying the object class.
| *obj*
| Object that owns `ad` (passed to the new callback).
| *ad*
| Ex‐data table to allocate into.
| *idx*
| Index from CRYPTO_get_ex_new_index() (or a class helper).
|===


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