while (a)
{
ctx: while(b)
     {
         while (c)
         {
             if(d) break ctx;
             ...
         }
     }
     ...
}

error: expected ‘;’ before ‘ctx’
     break ctx;
error: ‘ctx’ was not declared in this scope
warning: label ‘ctx’ defined but not used [-Wunused-label]
 ctx: