title: why am i not able to declare sigset_t with std=c99?
body: <p>If i compile the below program with std=c99, i get an error, but the program compiles fine without the c99 flag. Why?</p>
  
  <pre><code>#include &lt;signal.h&gt;
  void x()
  {
      sigset_t dd;
  }
  
  int main(void)
  {
      x();
      return 0;
  }
  
  
  jim@cola temp]$ gcc -std=c99 blah.c -o blah
  blah.c: In function ‘x’:
  blah.c:9: error: ‘sigset_t’ undeclared (first use in this function)
  blah.c:9: error: (Each undeclared identifier is reported only once
  blah.c:9: error: for each function it appears in.)
  blah.c:9: error: expected ‘;’ before ‘dd’
  </code></pre>