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 - OpenSSL initialisation and deinitialisation functions
 #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(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);
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 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 opts parameter specifies which aspects of libcrypto
    should be initialised. Valid options are:
  - 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
      OPENSSL_INIT_LOAD_CRYPTO_STRINGS will be ignored.
- 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
      OPENSSL_INIT_NO_LOAD_CRYPTO_STRINGS will be ignored.
- 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
      OPENSSL_INIT_NO_ADD_ALL_CIPHERS will be ignored.
- 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
      OPENSSL_INIT_NO_ADD_ALL_CIPHERS will be ignored.
- 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
      OPENSSL_INIT_ADD_ALL_CIPHERS will be ignored.
- 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
      OPENSSL_INIT_ADD_ALL_DIGESTS will be ignored.
- OPENSSL_INIT_LOAD_CONFIG
- With this option an OpenSSL configuration file will be automatically
      loaded and used by calling OPENSSL_config(). This is not a default
      option for libcrypto. As of OpenSSL 1.1.1 this is a default option for
      libssl (see OPENSSL_init_ssl(3) for further details about libssl
      initialisation). See the description of OPENSSL_INIT_new(),
    below.
- 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.
- OPENSSL_INIT_ASYNC
- With this option the library with automatically initialise the libcrypto
      async sub-library (see ASYNC_start_job(3)). This is a default
      option.
- OPENSSL_INIT_ENGINE_RDRAND
- With this option the library will automatically load and initialise the
      RDRAND engine (if available). This not a default option.
- OPENSSL_INIT_ENGINE_DYNAMIC
- With this option the library will automatically load and initialise the
      dynamic engine. This not a default option.
- OPENSSL_INIT_ENGINE_OPENSSL
- With this option the library will automatically load and initialise the
      openssl engine. This not a default option.
- OPENSSL_INIT_ENGINE_CRYPTODEV
- With this option the library will automatically load and initialise the
      cryptodev engine (if available). This not a default option.
- OPENSSL_INIT_ENGINE_CAPI
- With this option the library will automatically load and initialise the
      CAPI engine (if available). This not a default option.
- OPENSSL_INIT_ENGINE_PADLOCK
- With this option the library will automatically load and initialise the
      padlock engine (if available). This not a default option.
- OPENSSL_INIT_ENGINE_AFALG
- With this option the library will automatically load and initialise the
      AFALG engine. This not a default option.
- 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.
- OPENSSL_INIT_ATFORK
- With this option the library will register its fork handlers. See
      OPENSSL_fork_prepare(3) for details.
- 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().
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
    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() function deallocates resources
    associated with the current thread. Typically this function will be called
    automatically by the library when the thread exits. This should only be
    called directly if resources should be freed at an earlier time, or under
    the circumstances described in the NOTES section below.
The OPENSSL_INIT_LOAD_CONFIG flag will load a configuration
    file, as with CONF_modules_load_file(3) with NULL filename and
    application name and the CONF_MFLAGS_IGNORE_MISSING_FILE,
    CONF_MFLAGS_IGNORE_RETURN_CODES and
    CONF_MFLAGS_DEFAULT_SECTION flags. The filename, application name,
    and flags can be customized by providing a non-null
    OPENSSL_INIT_SETTINGS object. The object can be allocated via
    OPENSSL_init_new(). The
    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
    CONF_MFLAGS_IGNORE_RETURN_CODES flag is not included, any errors in
    the configuration file will cause an error return from
    OPENSSL_init_crypto or indirectly OPENSSL_init_ssl(3). The
    object can be released with OPENSSL_INIT_free() when done.
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).
The functions OPENSSL_init_crypto, OPENSSL_atexit() and
  OPENSSL_INIT_set_config_appname() return 1 on success or 0 on error.
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.
Copyright 2016-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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>.