/in/foo.c: In function 'a':
/in/foo.c:4:7: warning: implicit declaration of function 'b' [-Wimplicit-function-declaration]
    4 | int l=b(s);
      |       ^
/in/foo.c:8:33: error: 't' undeclared (first use in this function)
    8 |                                 t=s[j];
      |                                 ^
/in/foo.c:8:33: note: each undeclared identifier is reported only once for each function it appears in