doc/man3/OPENSSL_init_crypto.pod - third_party/openssl - Git at Google

 =pod

 =head1 NAME

 OPENSSL_INIT_new, OPENSSL_INIT_set_config_filename,
 OPENSSL_INIT_set_config_appname, OPENSSL_INIT_set_config_file_flags,
 OPENSSL_INIT_free, OPENSSL_init_crypto, OPENSSL_cleanup, OPENSSL_atexit,
 OPENSSL_thread_stop_ex, OPENSSL_thread_stop - OpenSSL initialisation
 and deinitialisation functions

 =head1 SYNOPSIS

  #include <openssl/crypto.h>

  void OPENSSL_cleanup(void);
  int OPENSSL_init_crypto(uint64_t opts, const OPENSSL_INIT_SETTINGS *settings);
  int OPENSSL_atexit(void (*handler)(void));
  void OPENSSL_thread_stop_ex(OSSL_LIB_CTX *ctx);
  void OPENSSL_thread_stop(void);

  OPENSSL_INIT_SETTINGS *OPENSSL_INIT_new(void);
  int OPENSSL_INIT_set_config_filename(OPENSSL_INIT_SETTINGS *init,
                                       const char* filename);
  int OPENSSL_INIT_set_config_file_flags(OPENSSL_INIT_SETTINGS *init,
                                         unsigned long flags);
  int OPENSSL_INIT_set_config_appname(OPENSSL_INIT_SETTINGS *init,
                                      const char* name);
  void OPENSSL_INIT_free(OPENSSL_INIT_SETTINGS *init);

 =head1 DESCRIPTION

 During normal operation OpenSSL (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_crypto() can be used for this purpose for
 libcrypto (see also L<OPENSSL_init_ssl(3)> for the libssl
 equivalent).

 Numerous internal OpenSSL functions call OPENSSL_init_crypto().
 Therefore, in order to perform nondefault initialisation,
 OPENSSL_init_crypto() MUST be called by application code prior to
 any other OpenSSL function calls.

 The B<opts> parameter specifies which aspects of libcrypto should be
 initialised. Valid options are:

 =over 4

 =item OPENSSL_INIT_NO_LOAD_CRYPTO_STRINGS

 Suppress automatic loading of the libcrypto error strings. This option is
 not a default option. Once selected subsequent calls to
 OPENSSL_init_crypto() with the option
 B<OPENSSL_INIT_LOAD_CRYPTO_STRINGS> will be ignored.

 =item OPENSSL_INIT_LOAD_CRYPTO_STRINGS

 Automatic loading of the libcrypto error strings. With this option the
 library will automatically load the libcrypto error strings.
 This option is a default option. Once selected subsequent calls to
 OPENSSL_init_crypto() with the option
 B<OPENSSL_INIT_NO_LOAD_CRYPTO_STRINGS> will be ignored.

 =item OPENSSL_INIT_ADD_ALL_CIPHERS

 With this option the library will automatically load and make available all
 libcrypto ciphers. This option is a default option. Once selected subsequent
 calls to OPENSSL_init_crypto() with the option
 B<OPENSSL_INIT_NO_ADD_ALL_CIPHERS> will be ignored.

 =item OPENSSL_INIT_ADD_ALL_DIGESTS

 With this option the library will automatically load and make available all
 libcrypto digests. This option is a default option. Once selected subsequent
 calls to OPENSSL_init_crypto() with the option
 B<OPENSSL_INIT_NO_ADD_ALL_CIPHERS> will be ignored.

 =item OPENSSL_INIT_NO_ADD_ALL_CIPHERS

 With this option the library will suppress automatic loading of libcrypto
 ciphers. This option is not a default option. Once selected subsequent
 calls to OPENSSL_init_crypto() with the option
 B<OPENSSL_INIT_ADD_ALL_CIPHERS> will be ignored.

 =item OPENSSL_INIT_NO_ADD_ALL_DIGESTS

 With this option the library will suppress automatic loading of libcrypto
 digests. This option is not a default option. Once selected subsequent
 calls to OPENSSL_init_crypto() with the option
 B<OPENSSL_INIT_ADD_ALL_DIGESTS> will be ignored.

 =item OPENSSL_INIT_LOAD_CONFIG

 With this option an OpenSSL configuration file will be automatically loaded and
 used by calling OPENSSL_config(). This is a default option.
 Note that in OpenSSL 1.1.1 this was the default for libssl but not for
 libcrypto (see L<OPENSSL_init_ssl(3)> for further details about libssl
 initialisation).
 In OpenSSL 1.1.0 this was a nondefault option for both libssl and libcrypto.
 See the description of OPENSSL_INIT_new(), below.

 =item OPENSSL_INIT_NO_LOAD_CONFIG

 With this option the loading of OpenSSL configuration files will be suppressed.
 It is the equivalent of calling OPENSSL_no_config(). This is not a default
 option.

 =item OPENSSL_INIT_ASYNC

 With this option the library with automatically initialise the libcrypto async
 sub-library (see L<ASYNC_start_job(3)>). This is a default option.

 =item OPENSSL_INIT_ENGINE_RDRAND

 With this option the library will automatically load and initialise the
 RDRAND engine (if available). This not a default option and is deprecated
 in OpenSSL 3.0.

 =item OPENSSL_INIT_ENGINE_DYNAMIC

 With this option the library will automatically load and initialise the
 dynamic engine. This not a default option and is deprecated
 in OpenSSL 3.0.

 =item OPENSSL_INIT_ENGINE_OPENSSL

 With this option the library will automatically load and initialise the
 openssl engine. This not a default option and is deprecated
 in OpenSSL 3.0.

 =item OPENSSL_INIT_ENGINE_CRYPTODEV

 With this option the library will automatically load and initialise the
 cryptodev engine (if available). This not a default option and is deprecated
 in OpenSSL 3.0.

 =item OPENSSL_INIT_ENGINE_CAPI

 With this option the library will automatically load and initialise the
 CAPI engine (if available). This not a default option and is deprecated
 in OpenSSL 3.0.

 =item OPENSSL_INIT_ENGINE_PADLOCK

 With this option the library will automatically load and initialise the
 padlock engine (if available). This not a default option and is deprecated
 in OpenSSL 3.0.

 =item OPENSSL_INIT_ENGINE_AFALG

 With this option the library will automatically load and initialise the
 AFALG engine. This not a default option and is deprecated
 in OpenSSL 3.0.

 =item OPENSSL_INIT_ENGINE_ALL_BUILTIN

 With this option the library will automatically load and initialise all the
 built in engines listed above with the exception of the openssl and afalg
 engines. This not a default option and is deprecated
 in OpenSSL 3.0.

 =item OPENSSL_INIT_ATFORK

 With this option the library will register its fork handlers.
 See OPENSSL_fork_prepare(3) for details.

 =item OPENSSL_INIT_NO_ATEXIT

 By default OpenSSL will attempt to clean itself up when the process exits via an
 "atexit" handler. Using this option suppresses that behaviour. This means that
 the application will have to clean up OpenSSL explicitly using
 OPENSSL_cleanup().

 =back

 Multiple options may be combined together in a single call to
 OPENSSL_init_crypto(). For example:

  OPENSSL_init_crypto(OPENSSL_INIT_NO_ADD_ALL_CIPHERS
                      | OPENSSL_INIT_NO_ADD_ALL_DIGESTS, NULL);

 The OPENSSL_cleanup() function deinitialises OpenSSL (both libcrypto
 and libssl). All resources allocated by OpenSSL are freed. Typically there
 should be no need to call this function directly as it is initiated
 automatically on application exit. This is done via the standard C library
 atexit() function. In the event that the application will close in a manner
 that will not call the registered atexit() handlers then the application should
 call OPENSSL_cleanup() directly. Developers of libraries using OpenSSL
 are discouraged from calling this function and should instead, typically, rely
 on auto-deinitialisation. This is to avoid error conditions where both an
 application and a library it depends on both use OpenSSL, and the library
 deinitialises it before the application has finished using it.

 Once OPENSSL_cleanup() has been called the library cannot be reinitialised.
 Attempts to call OPENSSL_init_crypto() will fail and an ERR_R_INIT_FAIL error
 will be added to the error stack. Note that because initialisation has failed
 OpenSSL error strings will not be available, only an error code. This code can
 be put through the openssl errstr command line application to produce a human
 readable error (see L<openssl-errstr(1)>).

 The OPENSSL_atexit() function enables the registration of a
 function to be called during OPENSSL_cleanup(). Stop handlers are
 called after deinitialisation of resources local to a thread, but before other
 process wide resources are freed. In the event that multiple stop handlers are
 registered, no guarantees are made about the order of execution.

 The OPENSSL_thread_stop_ex() function deallocates resources associated
 with the current thread for the given OSSL_LIB_CTX B<ctx>. The B<ctx> parameter
 can be NULL in which case the default OSSL_LIB_CTX is used.

 Typically, this function will be called automatically by the library when
 the thread exits as long as the OSSL_LIB_CTX has not been freed before the thread
 exits. If OSSL_LIB_CTX_free() is called OPENSSL_thread_stop_ex will be called
 automatically for the current thread (but not any other threads that may have
 used this OSSL_LIB_CTX).

 OPENSSL_thread_stop_ex should be called on all threads that will exit after the
 OSSL_LIB_CTX is freed.
 Typically this is not necessary for the default OSSL_LIB_CTX (because all
 resources are cleaned up on library exit) except if thread local resources
 should be freed before library exit, or under the circumstances described in
 the NOTES section below.

 OPENSSL_thread_stop() is the same as OPENSSL_thread_stop_ex() except that the
 default OSSL_LIB_CTX is always used.

 The B<OPENSSL_INIT_LOAD_CONFIG> flag will load a configuration file, as with
 L<CONF_modules_load_file(3)> with NULL filename and application name and the
 B<CONF_MFLAGS_IGNORE_MISSING_FILE>, B<CONF_MFLAGS_IGNORE_RETURN_CODES>  and
 B<CONF_MFLAGS_DEFAULT_SECTION> flags.
 The filename, application name, and flags can be customized by providing a
 non-null B<OPENSSL_INIT_SETTINGS> object.
 The object can be allocated via B<OPENSSL_INIT_new()>.
 The B<OPENSSL_INIT_set_config_filename()> function can be used to specify a
 nondefault filename, which is copied and need not refer to persistent storage.
 Similarly, OPENSSL_INIT_set_config_appname() can be used to specify a
 nondefault application name.
 Finally, OPENSSL_INIT_set_file_flags can be used to specify nondefault flags.
 If the B<CONF_MFLAGS_IGNORE_RETURN_CODES> flag is not included, any errors in
 the configuration file will cause an error return from B<OPENSSL_init_crypto>
 or indirectly L<OPENSSL_init_ssl(3)>.
 The object can be released with OPENSSL_INIT_free() when done.

 =head1 NOTES

 Resources local to a thread are deallocated automatically when the thread exits
 (e.g. in a pthreads environment, when pthread_exit() is called). On Windows
 platforms this is done in response to a DLL_THREAD_DETACH message being sent to
 the libcrypto32.dll entry point. Some windows functions may cause threads to exit
 without sending this message (for example ExitProcess()). If the application
 uses such functions, then the application must free up OpenSSL resources
 directly via a call to OPENSSL_thread_stop() on each thread. Similarly this
 message will also not be sent if OpenSSL is linked statically, and therefore
 applications using static linking should also call OPENSSL_thread_stop() on each
 thread. Additionally if OpenSSL is loaded dynamically via LoadLibrary() and the
 threads are not destroyed until after FreeLibrary() is called then each thread
 should call OPENSSL_thread_stop() prior to the FreeLibrary() call.

 On Linux/Unix where OpenSSL has been loaded via dlopen() and the application is
 multi-threaded and if dlclose() is subsequently called prior to the threads
 being destroyed then OpenSSL will not be able to deallocate resources associated
 with those threads. The application should either call OPENSSL_thread_stop() on
 each thread prior to the dlclose() call, or alternatively the original dlopen()
 call should use the RTLD_NODELETE flag (where available on the platform).

 =head1 RETURN VALUES

 The functions OPENSSL_init_crypto, OPENSSL_atexit() and
 OPENSSL_INIT_set_config_appname() return 1 on success or 0 on error.

 =head1 SEE ALSO

 L<OPENSSL_init_ssl(3)>

 =head1 HISTORY

 The OPENSSL_init_crypto(), OPENSSL_cleanup(), OPENSSL_atexit(),
 OPENSSL_thread_stop(), OPENSSL_INIT_new(), OPENSSL_INIT_set_config_appname()
 and OPENSSL_INIT_free() functions were added in OpenSSL 1.1.0.

 =head1 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
 L<https://www.openssl.org/source/license.html>.

 =cut
	=pod

	=head1 NAME

	OPENSSL_INIT_new, OPENSSL_INIT_set_config_filename,
	OPENSSL_INIT_set_config_appname, OPENSSL_INIT_set_config_file_flags,
	OPENSSL_INIT_free, OPENSSL_init_crypto, OPENSSL_cleanup, OPENSSL_atexit,
	OPENSSL_thread_stop_ex, OPENSSL_thread_stop - OpenSSL initialisation
	and deinitialisation functions

	=head1 SYNOPSIS

	#include <openssl/crypto.h>

	void OPENSSL_cleanup(void);
	int OPENSSL_init_crypto(uint64_t opts, const OPENSSL_INIT_SETTINGS *settings);
	int OPENSSL_atexit(void (*handler)(void));
	void OPENSSL_thread_stop_ex(OSSL_LIB_CTX *ctx);
	void OPENSSL_thread_stop(void);

	OPENSSL_INIT_SETTINGS *OPENSSL_INIT_new(void);
	int OPENSSL_INIT_set_config_filename(OPENSSL_INIT_SETTINGS *init,
	const char* filename);
	int OPENSSL_INIT_set_config_file_flags(OPENSSL_INIT_SETTINGS *init,
	unsigned long flags);
	int OPENSSL_INIT_set_config_appname(OPENSSL_INIT_SETTINGS *init,
	const char* name);
	void OPENSSL_INIT_free(OPENSSL_INIT_SETTINGS *init);

	=head1 DESCRIPTION

	During normal operation OpenSSL (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_crypto() can be used for this purpose for
	libcrypto (see also L<OPENSSL_init_ssl(3)> for the libssl
	equivalent).

	Numerous internal OpenSSL functions call OPENSSL_init_crypto().
	Therefore, in order to perform nondefault initialisation,
	OPENSSL_init_crypto() MUST be called by application code prior to
	any other OpenSSL function calls.

	The B<opts> parameter specifies which aspects of libcrypto should be
	initialised. Valid options are:

	=over 4

	=item OPENSSL_INIT_NO_LOAD_CRYPTO_STRINGS

	Suppress automatic loading of the libcrypto error strings. This option is
	not a default option. Once selected subsequent calls to
	OPENSSL_init_crypto() with the option
	B<OPENSSL_INIT_LOAD_CRYPTO_STRINGS> will be ignored.

	=item OPENSSL_INIT_LOAD_CRYPTO_STRINGS

	Automatic loading of the libcrypto error strings. With this option the
	library will automatically load the libcrypto error strings.
	This option is a default option. Once selected subsequent calls to
	OPENSSL_init_crypto() with the option
	B<OPENSSL_INIT_NO_LOAD_CRYPTO_STRINGS> will be ignored.

	=item OPENSSL_INIT_ADD_ALL_CIPHERS

	With this option the library will automatically load and make available all
	libcrypto ciphers. This option is a default option. Once selected subsequent
	calls to OPENSSL_init_crypto() with the option
	B<OPENSSL_INIT_NO_ADD_ALL_CIPHERS> will be ignored.

	=item OPENSSL_INIT_ADD_ALL_DIGESTS

	With this option the library will automatically load and make available all
	libcrypto digests. This option is a default option. Once selected subsequent
	calls to OPENSSL_init_crypto() with the option
	B<OPENSSL_INIT_NO_ADD_ALL_CIPHERS> will be ignored.

	=item OPENSSL_INIT_NO_ADD_ALL_CIPHERS

	With this option the library will suppress automatic loading of libcrypto
	ciphers. This option is not a default option. Once selected subsequent
	calls to OPENSSL_init_crypto() with the option
	B<OPENSSL_INIT_ADD_ALL_CIPHERS> will be ignored.

	=item OPENSSL_INIT_NO_ADD_ALL_DIGESTS

	With this option the library will suppress automatic loading of libcrypto
	digests. This option is not a default option. Once selected subsequent
	calls to OPENSSL_init_crypto() with the option
	B<OPENSSL_INIT_ADD_ALL_DIGESTS> will be ignored.

	=item OPENSSL_INIT_LOAD_CONFIG

	With this option an OpenSSL configuration file will be automatically loaded and
	used by calling OPENSSL_config(). This is a default option.
	Note that in OpenSSL 1.1.1 this was the default for libssl but not for
	libcrypto (see L<OPENSSL_init_ssl(3)> for further details about libssl
	initialisation).
	In OpenSSL 1.1.0 this was a nondefault option for both libssl and libcrypto.
	See the description of OPENSSL_INIT_new(), below.

	=item OPENSSL_INIT_NO_LOAD_CONFIG

	With this option the loading of OpenSSL configuration files will be suppressed.
	It is the equivalent of calling OPENSSL_no_config(). This is not a default
	option.

	=item OPENSSL_INIT_ASYNC

	With this option the library with automatically initialise the libcrypto async
	sub-library (see L<ASYNC_start_job(3)>). This is a default option.

	=item OPENSSL_INIT_ENGINE_RDRAND

	With this option the library will automatically load and initialise the
	RDRAND engine (if available). This not a default option and is deprecated
	in OpenSSL 3.0.

	=item OPENSSL_INIT_ENGINE_DYNAMIC

	With this option the library will automatically load and initialise the
	dynamic engine. This not a default option and is deprecated
	in OpenSSL 3.0.

	=item OPENSSL_INIT_ENGINE_OPENSSL

	With this option the library will automatically load and initialise the
	openssl engine. This not a default option and is deprecated
	in OpenSSL 3.0.

	=item OPENSSL_INIT_ENGINE_CRYPTODEV

	With this option the library will automatically load and initialise the
	cryptodev engine (if available). This not a default option and is deprecated
	in OpenSSL 3.0.

	=item OPENSSL_INIT_ENGINE_CAPI

	With this option the library will automatically load and initialise the
	CAPI engine (if available). This not a default option and is deprecated
	in OpenSSL 3.0.

	=item OPENSSL_INIT_ENGINE_PADLOCK

	With this option the library will automatically load and initialise the
	padlock engine (if available). This not a default option and is deprecated
	in OpenSSL 3.0.

	=item OPENSSL_INIT_ENGINE_AFALG

	With this option the library will automatically load and initialise the
	AFALG engine. This not a default option and is deprecated
	in OpenSSL 3.0.

	=item OPENSSL_INIT_ENGINE_ALL_BUILTIN

	With this option the library will automatically load and initialise all the
	built in engines listed above with the exception of the openssl and afalg
	engines. This not a default option and is deprecated
	in OpenSSL 3.0.

	=item OPENSSL_INIT_ATFORK

	With this option the library will register its fork handlers.
	See OPENSSL_fork_prepare(3) for details.

	=item OPENSSL_INIT_NO_ATEXIT

	By default OpenSSL will attempt to clean itself up when the process exits via an
	"atexit" handler. Using this option suppresses that behaviour. This means that
	the application will have to clean up OpenSSL explicitly using
	OPENSSL_cleanup().

	=back

	Multiple options may be combined together in a single call to
	OPENSSL_init_crypto(). For example:

	OPENSSL_init_crypto(OPENSSL_INIT_NO_ADD_ALL_CIPHERS
	\| OPENSSL_INIT_NO_ADD_ALL_DIGESTS, NULL);

	The OPENSSL_cleanup() function deinitialises OpenSSL (both libcrypto
	and libssl). All resources allocated by OpenSSL are freed. Typically there
	should be no need to call this function directly as it is initiated
	automatically on application exit. This is done via the standard C library
	atexit() function. In the event that the application will close in a manner
	that will not call the registered atexit() handlers then the application should
	call OPENSSL_cleanup() directly. Developers of libraries using OpenSSL
	are discouraged from calling this function and should instead, typically, rely
	on auto-deinitialisation. This is to avoid error conditions where both an
	application and a library it depends on both use OpenSSL, and the library
	deinitialises it before the application has finished using it.

	Once OPENSSL_cleanup() has been called the library cannot be reinitialised.
	Attempts to call OPENSSL_init_crypto() will fail and an ERR_R_INIT_FAIL error
	will be added to the error stack. Note that because initialisation has failed
	OpenSSL error strings will not be available, only an error code. This code can
	be put through the openssl errstr command line application to produce a human
	readable error (see L<openssl-errstr(1)>).

	The OPENSSL_atexit() function enables the registration of a
	function to be called during OPENSSL_cleanup(). Stop handlers are
	called after deinitialisation of resources local to a thread, but before other
	process wide resources are freed. In the event that multiple stop handlers are
	registered, no guarantees are made about the order of execution.

	The OPENSSL_thread_stop_ex() function deallocates resources associated
	with the current thread for the given OSSL_LIB_CTX B<ctx>. The B<ctx> parameter
	can be NULL in which case the default OSSL_LIB_CTX is used.

	Typically, this function will be called automatically by the library when
	the thread exits as long as the OSSL_LIB_CTX has not been freed before the thread
	exits. If OSSL_LIB_CTX_free() is called OPENSSL_thread_stop_ex will be called
	automatically for the current thread (but not any other threads that may have
	used this OSSL_LIB_CTX).

	OPENSSL_thread_stop_ex should be called on all threads that will exit after the
	OSSL_LIB_CTX is freed.
	Typically this is not necessary for the default OSSL_LIB_CTX (because all
	resources are cleaned up on library exit) except if thread local resources
	should be freed before library exit, or under the circumstances described in
	the NOTES section below.

	OPENSSL_thread_stop() is the same as OPENSSL_thread_stop_ex() except that the
	default OSSL_LIB_CTX is always used.

	The B<OPENSSL_INIT_LOAD_CONFIG> flag will load a configuration file, as with
	L<CONF_modules_load_file(3)> with NULL filename and application name and the
	B<CONF_MFLAGS_IGNORE_MISSING_FILE>, B<CONF_MFLAGS_IGNORE_RETURN_CODES> and
	B<CONF_MFLAGS_DEFAULT_SECTION> flags.
	The filename, application name, and flags can be customized by providing a
	non-null B<OPENSSL_INIT_SETTINGS> object.
	The object can be allocated via B<OPENSSL_INIT_new()>.
	The B<OPENSSL_INIT_set_config_filename()> function can be used to specify a
	nondefault filename, which is copied and need not refer to persistent storage.
	Similarly, OPENSSL_INIT_set_config_appname() can be used to specify a
	nondefault application name.
	Finally, OPENSSL_INIT_set_file_flags can be used to specify nondefault flags.
	If the B<CONF_MFLAGS_IGNORE_RETURN_CODES> flag is not included, any errors in
	the configuration file will cause an error return from B<OPENSSL_init_crypto>
	or indirectly L<OPENSSL_init_ssl(3)>.
	The object can be released with OPENSSL_INIT_free() when done.

	=head1 NOTES

	Resources local to a thread are deallocated automatically when the thread exits
	(e.g. in a pthreads environment, when pthread_exit() is called). On Windows
	platforms this is done in response to a DLL_THREAD_DETACH message being sent to
	the libcrypto32.dll entry point. Some windows functions may cause threads to exit
	without sending this message (for example ExitProcess()). If the application
	uses such functions, then the application must free up OpenSSL resources
	directly via a call to OPENSSL_thread_stop() on each thread. Similarly this
	message will also not be sent if OpenSSL is linked statically, and therefore
	applications using static linking should also call OPENSSL_thread_stop() on each
	thread. Additionally if OpenSSL is loaded dynamically via LoadLibrary() and the
	threads are not destroyed until after FreeLibrary() is called then each thread
	should call OPENSSL_thread_stop() prior to the FreeLibrary() call.

	On Linux/Unix where OpenSSL has been loaded via dlopen() and the application is
	multi-threaded and if dlclose() is subsequently called prior to the threads
	being destroyed then OpenSSL will not be able to deallocate resources associated
	with those threads. The application should either call OPENSSL_thread_stop() on
	each thread prior to the dlclose() call, or alternatively the original dlopen()
	call should use the RTLD_NODELETE flag (where available on the platform).

	=head1 RETURN VALUES

	The functions OPENSSL_init_crypto, OPENSSL_atexit() and
	OPENSSL_INIT_set_config_appname() return 1 on success or 0 on error.

	=head1 SEE ALSO

	L<OPENSSL_init_ssl(3)>

	=head1 HISTORY

	The OPENSSL_init_crypto(), OPENSSL_cleanup(), OPENSSL_atexit(),
	OPENSSL_thread_stop(), OPENSSL_INIT_new(), OPENSSL_INIT_set_config_appname()
	and OPENSSL_INIT_free() functions were added in OpenSSL 1.1.0.

	=head1 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
	L<https://www.openssl.org/source/license.html>.

	=cut