OpenSSL update into newer version: Alternative for the deprecated `OPENSSL_config`

Question

In my C project I updated the OpenSSl library 1.0.2g into newer one (1.1.x versions) while I was compiling my code I had the following warning thrown:

main.c:40:3: warning: ‘OPENSSL_config’ is deprecated [-Wdeprecated-declarations] OPENSSL_config(NULL);

The code throwing this error is:

#include <stdio.h>

// Openssl
#include <openssl/conf.h>
#include <openssl/evp.h>
#include <openssl/err.h>

int main(int argc, char *argv[]) {
  /* Load the human readable error strings for libcrypto */
  ERR_load_crypto_strings();
  /* Load all digest and cipher algorithms */
  OpenSSL_add_all_algorithms();
  /* Load config file, and other important initialisation */
  OPENSSL_config(NULL);

  //Come code here

  EVP_cleanup();
  CRYPTO_cleanup_all_ex_data();
  ERR_free_strings();
  return 0;
}

So as the best practices dictate I should avoid and use alternative approaches on deprecated functions in my case which one should I use?

Answer 1

The OPENSSL_config says it all:

This function is deprecated and its use should be avoided. Applications should instead call CONF_modules_load() during initialization (that is before starting any threads).

Also SSL_load_error_strings and OpenSSL_add_all_algorithms are also deprecated as well.

For openssl >= 1.1 you can remove the your whole startup and cleanup code above as it's not needed any longer. It's all done automatically now for you.