=pod

=head1 NAME

OPENSSL_INIT_ssl_library_start - OpenSSL (libssl and libcrypto) initialisation

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 void OPENSSL_INIT_ssl_library_start(uint64_t opts,
                                     const OPENSSL_INIT_SETTINGS *settings);

=head1 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 way be situations when explicit initialisation is desirable or
needed, for example when some non-default initialisation is required. The
function OPENSSL_INIT_ssl_library_start() can be used for this purpose. Calling
this function will explicitly initialise BOTH libcrypto and libssl. To
explicitly initialise ONLY libcrypto see the
L<OPENSSL_INIT_crypto_library_start(3)> function. In order to perform
non-default initialisation it MUST be called prior to any other calls of this
function. As numerous internal OpenSSL functions also call this, this usually
means you should call it prior to ANY other OpenSSL function calls.

The B<opts> parameter specifies which aspects of libssl and libcrypto should be
initialised. Valid options for libcrypto are described on the
L<OPENSSL_INIT_crypto_library_start(3)> page. In addition to any libcrypto
specific option the following libssl options can also be used:

=over 4

=item OPENSSL_INIT_NO_LOAD_SSL_STRINGS

Suppress automatic loading of the libssl error strings. With this option the
library will not automatically call ERR_load_SSL_strings(). This option is
not a default option. Once selected subsequent calls to
OPENSSL_INIT_ssl_library_start() with the option
B<OPENSSL_INIT_LOAD_SSL_STRINGS> will be ignored. Applications may call
ERR_load_SSL_strings() directly if they wish even if this option has been
selected. If they do so then they must also explicitly call ERR_free_strings()
on application close down.

=item OPENSSL_INIT_LOAD_SSL_STRINGS

Automatic loading of the libssl error strings. With this option the
library will automatically call ERR_load_SSL_strings(). This option is a
default option. Once selected subsequent calls to
OPENSSL_INIT_ssl_library_start() with the option
B<OPENSSL_INIT_LOAD_SSL_STRINGS> will be ignored.

=back

The B<settings> parameter specifies optional settings values to an option.
Currently no such settings are available for libssl specific options. However
these settings will also be passed internally to a call to
L<OPENSSL_INIT_crypto_library_start(3)>, so this parameter can also be used to
provide libcrypto settings values.

=head1 SEE ALSO

L<OPENSSL_INIT_crypto_library_start(3)>

=head1 HISTORY

The OPENSSL_INIT_ssl_library_start function was first added in OpenSSL 1.1.0.

=cut