why c local variable need translated to void?

Question

recently I'm studying a project in github,and I found this.why there is a "(void)n" in the end?

void CurrentThread::cacheTid()
{
  if (t_cachedTid == 0)
  {
    t_cachedTid = detail::gettid();
    int n = snprintf(t_tidString, sizeof t_tidString, "%5d ", t_cachedTid);
    assert(n == 6); (void) n;
  }
}

Answer 1

(void)n is effectively a no-op. However, it will prevent the compiler from issuing an "unused variable" warning when assertions are turned off and the preceding assert() is compiled out.

Answer 2

This construction suppresses warning about declared, but never used variable