[#BN_MONT_CTX_set_locked]
= BN_MONT_CTX_set_locked
:mrdocs:

Lazily initialize a shared Montgomery context under a lock.

== Synopsis

Declared in `<openssl/bn.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:BN_MONT_CTX.adoc[BN_MONT_CTX]*
BN_MONT_CTX_set_locked(
    xref:BN_MONT_CTX.adoc[BN_MONT_CTX]** pmont,
    xref:CRYPTO_RWLOCK.adoc[CRYPTO_RWLOCK]* lock,
    xref:BIGNUM.adoc[BIGNUM] const* mod,
    xref:BN_CTX.adoc[BN_CTX]* ctx);
----

== Return Value

The initialized Montgomery context at *`pmont,` or NULL on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *pmont*
| Address of the Montgomery context pointer; allocated and set on first use.
| *lock*
| Read/write lock serializing initialization of *`pmont.`
| *mod*
| Modulus used to build the Montgomery context.
| *ctx*
| BN_CTX scratch space for the initialization.
|===


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