title: SHA_DIGEST_LENGTH undefined
body: <p>So currently my code looks something like this:</p>
  
  <pre><code>int main(){
      char input[1024]
      size_t length;
      unsigned char hash[SHA_DIGEST_LENGTH];
      fgets(input,1024,stdin);
      length = sizeof(input);
      SHA(input,hash,length)
  }
  </code></pre>
  
  <p>I receive a compilation error telling me that <code>SHA_DIGEST_LENGTH</code> is undefined. I thought when compiling including <code>-lssl</code> and <code>-lcrypto</code> would sort of define it for me?</p>