编辑期间对HMAC API的不确定引用

Question

我在下面附上了一个代码段，该代码段是使用OpenSSL V1.0.2U HMAC API创建消息身份验证的代码（MAC）的。我在编译代码时遇到了麻烦。

int main() {
        // The secret key for hashing
        const char key[] = "012345678";
        // The data that we're going to hash
        char data[] = "hello world";
        // Be careful of the length of string with the choosen hash engine. SHA1 needed 20 characters.
        // Change the length accordingly with your choosen hash engine.
        unsigned char* result;
        unsigned int len = 20;
        result = (unsigned char*)malloc(sizeof(char) * len);
        HMAC_CTX *ctx;
        //ctx = HMAC_CTX_new();
        HMAC_CTX_init(&ctx);
        // Using sha1 hash engine here.
        // You may use other hash engines. e.g EVP_md5(), EVP_sha224, EVP_sha512, etc
        HMAC_Init_ex(&ctx, key, strlen(key), EVP_sha1(), NULL);
        HMAC_Update(&ctx, (unsigned char*)&data, strlen(data));
        HMAC_Final(&ctx, result, &len);
        HMAC_CTX_free(&ctx);
        printf("HMAC digest: ");
        for (int i = 0; i != len; i++)
                printf("%02x", (unsigned int)result[i]);
        printf("\n");
        free(result);
        return 0;
}

用于编译的命令：

gcc -I/usr/local/ssl/include, main.c -Wl,-L/usr/local/ssl/lib -lssl -lcrypto

输出：汇编失败了以下错误：

main.c:(.text+0x66): undefined reference to `HMAC_CTX_init'
collect2: error: ld returned 1 exit status

有人可以在这里帮助我吗？