foo.c: In function ‘main’:
foo.c:21:18: warning: format ‘%f’ expects argument of type ‘double’, but argument 2 has type ‘int *’ [-Wformat=]
   21 |         printf("%f\n",&signal);
      |                 ~^    ~~~~~~~
      |                  |    |
      |                  |    int *
      |                  double
      |                 %ls