foo.c: In function ‘main’:
foo.c:5:12: warning: zero-length gnu_printf format string [-Wformat-zero-length]
    5 |     printf("");
      |            ^~
foo.c:10:43: warning: implicit declaration of function ‘pow’ [-Wimplicit-function-declaration]
   10 |     long long newNum = digit * (long long)pow(10, (int)log10(num) + 1) + num;
      |                                           ^~~
foo.c:2:1: note: include ‘<math.h>’ or provide a declaration of ‘pow’
    1 | #include <stdio.h>
  +++ |+#include <math.h>
    2 | 
foo.c:10:43: warning: incompatible implicit declaration of built-in function ‘pow’ [-Wbuiltin-declaration-mismatch]
   10 |     long long newNum = digit * (long long)pow(10, (int)log10(num) + 1) + num;
      |                                           ^~~
foo.c:10:43: note: include ‘<math.h>’ or provide a declaration of ‘pow’
foo.c:10:56: warning: implicit declaration of function ‘log10’ [-Wimplicit-function-declaration]
   10 |     long long newNum = digit * (long long)pow(10, (int)log10(num) + 1) + num;
      |                                                        ^~~~~
foo.c:10:56: note: include ‘<math.h>’ or provide a declaration of ‘log10’
foo.c:10:56: warning: incompatible implicit declaration of built-in function ‘log10’ [-Wbuiltin-declaration-mismatch]
foo.c:10:56: note: include ‘<math.h>’ or provide a declaration of ‘log10’