foo.c: In function 'len':
foo.c:17:18: warning: format '%d' expects argument of type 'int', but argument 2 has type 'size_t' {aka 'long unsigned int'} [-Wformat=]
   17 |         printf("%d\n", strlen(a));
      |                 ~^     ~~~~~~~~~
      |                  |     |
      |                  int   size_t {aka long unsigned int}
      |                 %ld
foo.c:18:18: warning: format '%d' expects argument of type 'int', but argument 2 has type 'size_t' {aka 'long unsigned int'} [-Wformat=]
   18 |         printf("%d\n", strlen(b));
      |                 ~^     ~~~~~~~~~
      |                  |     |
      |                  int   size_t {aka long unsigned int}
      |                 %ld

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