char* convert_public_key_and_private_wif_to_pubkey(const char* pub_key, const char* priv_key) {
    EC_GROUP* ecgrp;
    EC_KEY* miner_key;
    EC_POINT* tmpg;
    EC_POINT* ppnt;
    BIGNUM order;
    BIGNUM cofactor;
    BIGNUM bnbase;
    BIGNUM bnpriv;
   
   
    unsigned char eckey_buf[128], *pend;
   
    // Init BiGNUMs
    BN_init(&bnbase);
    BN_init(&order);
    BN_init(&cofactor);
    BN_init(&bnpriv);
   
    // Set Bignum Base.
    BN_set_word(&bnbase, 58);
   
    // Init Context.
    BN_CTX bnctx = BN_CTX_new();
   
    // Init Curve.
    ecgrp = EC_GROUP_new_by_curve_name(NID_secp256k1);
    miner_key = EC_KEY_new_by_curve_name(NID_secp256k1);
   
    // Init Group from Public Key.
    tmpg = EC_POINT_hex2point(ecgrp, pub_key, NULL, NULL);
   
    // Get group order.
    EC_GROUP_get_order(ecgrp, &order, NULL);
   
    // Get Cofactor.
    EC_GROUP_get_cofactor(ecgrp, &cofactor, NULL);
   
    // Set Generator.
    EC_GROUP_set_generator(ecgrp, tmpg, &order, &cofactor);
   
    // Init Key.
    EC_KEY bnkey = EC_KEY_new();
   
    // Set key group.
    EC_KEY_set_group(bnkey, ecgrp);
    EC_GROUP pgroup = EC_KEY_get0_group(miner_key);
    ppnt = EC_POINT_new(pgroup);
   
    // Precompute.
    EC_KEY_precompute_mult(bnkey, bnctx);
   
    // Set private key.
    BN_init(&bnpriv);
    BN_bin2bn(priv_key, 64, &bnpriv);
    EC_KEY_set_private_key(miner_key, bnpriv);
    EC_POINT_mul(pgroup, ppnt, miner_key, NULL, NULL, NULL);
    EC_KEY_set_public_key(miner_key, ppnt);
   
    // Add keys together.
    BN_mod_add(&order,
               EC_KEY_get0_private_key(bnkey),
       EC_KEY_get0_private_key(miner_key),
               &cofactor,
               bnctx);

    // Get and return public key.
    pend = eckey_buf;
    i2o_ECPublicKey(bnkey, &pend);
    return pend;
}

util.c: In function 'convert_public_key_and_private_wif_to_pubkey':
util.c:48:5: error: variable 'bnctx' has initializer but incomplete type
     BN_CTX bnctx = BN_CTX_new();
     ^
util.c:48:12: error: storage size of 'bnctx' isn't known
     BN_CTX bnctx = BN_CTX_new();
            ^
util.c:67:5: error: variable 'bnkey' has initializer but incomplete type
     EC_KEY bnkey = EC_KEY_new();
     ^
util.c:67:12: error: storage size of 'bnkey' isn't known
     EC_KEY bnkey = EC_KEY_new();
            ^
util.c:71:5: error: variable 'pgroup' has initializer but incomplete type
     EC_GROUP pgroup = EC_KEY_get0_group(miner_key);
     ^
util.c:71:14: error: storage size of 'pgroup' isn't known
     EC_GROUP pgroup = EC_KEY_get0_group(miner_key);
              ^
util.c:79:15: warning: pointer targets in passing argument 1 of 'BN_bin2bn' differ in signedness [-Wpointer-sign]
     BN_bin2bn(priv_key, 64, &bnpriv);
               ^
In file included from util.c:5:0:
/usr/include/openssl/bn.h:442:9: note: expected 'const unsigned char *' but argument is of type 'const char *'
 BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret);
         ^
util.c:80:39: error: incompatible type for argument 2 of 'EC_KEY_set_private_key'
     EC_KEY_set_private_key(miner_key, bnpriv);
                                       ^
In file included from util.c:6:0:
/usr/include/openssl/ec.h:819:5: note: expected 'const BIGNUM * {aka const struct bignum_st *}' but argument is of type 'BIGNUM {aka struct bignum_st}'
 int EC_KEY_set_private_key(EC_KEY *key, const BIGNUM *prv);
     ^
util.c:81:32: warning: passing argument 3 of 'EC_POINT_mul' from incompatible pointer type [-Wincompatible-pointer-types]
     EC_POINT_mul(pgroup, ppnt, miner_key, NULL, NULL, NULL);
                                ^
In file included from util.c:6:0:
/usr/include/openssl/ec.h:685:5: note: expected 'const BIGNUM * {aka const struct bignum_st *}' but argument is of type 'EC_KEY * {aka struct ec_key_st *}'
 int EC_POINT_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *n,
     ^
util.c:94:12: warning: pointer targets in return differ in signedness [-Wpointer-sign]
     return pend;
            ^
util.c:71:14: warning: unused variable 'pgroup' [-Wunused-variable]
     EC_GROUP pgroup = EC_KEY_get0_group(miner_key);
              ^
util.c:67:12: warning: unused variable 'bnkey' [-Wunused-variable]
     EC_KEY bnkey = EC_KEY_new();
            ^
util.c:48:12: warning: unused variable 'bnctx' [-Wunused-variable]
     BN_CTX bnctx = BN_CTX_new();
            ^
make: *** [: util.o] Error 1

BUILD FAILED (exit value 2, total time: 8s)