devdocs/c/language%2Fattributes%2Ffallthrough.html


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    <h1 id="firstHeading" class="firstHeading">C attribute: fallthrough <span class="t-mark-rev t-since-c23">(since C23)</span>
</h1>            <p>Indicates that the fall through from the previous case label is intentional and should not be diagnosed by a compiler that warns on fallthrough.</p>
<h3 id="Syntax"> Syntax</h3> <table class="t-sdsc-begin">  <tr class="t-sdsc"> <td class="t-sdsc-nopad"> <code>[[</code> <code>fallthrough</code> <code>]]</code><br><code>[[</code> <code>__fallthrough__</code> <code>]]</code> </td> <td class="t-sdsc-nopad"> </td> <td class="t-sdsc-nopad"> </td>
</tr> 
</table> <h3 id="Explanation"> Explanation</h3> <p>May only be used in an <a href="../declarations" title="c/language/declarations">attribute declaration</a> to create a <i>fallthrough declaration</i> (<code>[[fallthrough]];</code>).</p>
<p>A fallthrough declaration may only be used in a <a href="../switch" title="c/language/switch"><code>switch</code></a> statement, where the next block item (statement, declaration, or label) to be encounted is a statement with a <code>case</code> or <code>default</code> label for that switch statement.</p>
<p>Indicates that the fall through from the previous case label is intentional and should not be diagnosed by a compiler that warns on fallthrough.</p>
<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include &lt;stdbool.h&gt;
 
void g(void) {}
void h(void) {}
void i(void) {}
 
void f(int n) {
  switch (n) {
    case 1:
    case 2:
      g();
     [[fallthrough]];
    case 3: // no warning on fallthrough
      h();
    case 4: // compiler may warn on fallthrough
      if(n &lt; 3) {
          i();
          [[fallthrough]]; // OK
      }
      else {
          return;
      }
    case 5:
      while (false) {
        [[fallthrough]]; // ill-formed: no subsequent case or default label
      }
    case 6:
      [[fallthrough]]; // ill-formed: no subsequent case or default label
  }
}
 
int main(void) {}</pre></div> </div> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/language/attributes/fallthrough" title="cpp/language/attributes/fallthrough">C++ documentation</a></span> for <code>fallthrough</code> </td>
</tr> </table>           <div class="_attribution">
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