title: warning: passing argument 2 of ‘fopen’ makes pointer from integer without a cast
body: <p>I have this function to check if a file exists:</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  
  int main(int argc, char **argv) {
      int textFileExists(const char *filename){
          FILE *fp=   fopen(filename,'r');
          if(fp==NULL){
              printf("%s %s.\n","There was an error opening ", filename);
              return -1;
          }
          return 1;
      }
  
      textFileExists("text.txt");
      return 0;
  }
  </code></pre>
  
  <p>But when I compile this code, I get this warning.</p>
  
  <pre><code>warning: passing argument 2 of ‘fopen’ makes pointer from integer without a cast
    FILE *fp= fopen(filename,'r');
  </code></pre>
  
  <p>Running this code gives me a segmentation fault.</p>
  
  <p>What is going on here?</p>