OPENSSL_INIT_SSL(3SSL) OpenSSL OPENSSL_INIT_SSL(3SSL)
NAME
OPENSSL_init_ssl - OpenSSL (libssl and libcrypto) initialisation
SYNOPSIS
#include <openssl/ssl.h>
int OPENSSL_init_ssl(uint64_t opts, const OPENSSL_INIT_SETTINGS *settings);
DESCRIPTION
During normal operation OpenSSL (libssl and libcrypto) will allocate
various resources at start up that must, subsequently, be freed on close
down of the library. Additionally some resources are allocated on a per
thread basis (if the application is multi-threaded), and these resources
must be freed prior to the thread closing.
As of version 1.1.0 OpenSSL will automatically allocate all resources
that it needs so no explicit initialisation is required. Similarly it
will also automatically deinitialise as required.
However, there may be situations when explicit initialisation is
desirable or needed, for example when some nondefault initialisation is
required. The function OPENSSL_init_ssl() can be used for this purpose.
Calling this function will explicitly initialise BOTH libcrypto and
libssl. To explicitly initialise ONLY libcrypto see the
OPENSSL_init_crypto(3) function.
Numerous internal OpenSSL functions call OPENSSL_init_ssl(). Therefore,
in order to perform nondefault initialisation, OPENSSL_init_ssl() MUST
be called by application code prior to any other OpenSSL function calls.
The opts parameter specifies which aspects of libssl and libcrypto
should be initialised. Valid options for libcrypto are described on the
OPENSSL_init_crypto(3) page. In addition to any libcrypto specific
option the following libssl options can also be used:
OPENSSL_INIT_NO_LOAD_SSL_STRINGS
Suppress automatic loading of the libssl error strings. This option
is not a default option. Once selected subsequent calls to
OPENSSL_init_ssl() with the option OPENSSL_INIT_LOAD_SSL_STRINGS
will be ignored.
OPENSSL_INIT_LOAD_SSL_STRINGS
Automatic loading of the libssl error strings. This option is a
default option. Once selected subsequent calls to OPENSSL_init_ssl()
with the option OPENSSL_INIT_LOAD_SSL_STRINGS will be ignored.
OPENSSL_init_ssl() takes a settings parameter which can be used to set
parameter values. See OPENSSL_init_crypto(3) for details.
RETURN VALUES
The function OPENSSL_init_ssl() returns 1 on success or 0 on error.
SEE ALSO
OPENSSL_init_crypto(3)
HISTORY
The OPENSSL_init_ssl() function was added in OpenSSL 1.1.0.
COPYRIGHT
Copyright 2016-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
3.5.7 2026-06-09 OPENSSL_INIT_SSL(3SSL)
Generated by dwww version 1.16 on Sat Oct 3 03:32:19 CEST 2026.