/in/foo.c: In function 'isPalindrome':
/in/foo.c:12:25: warning: implicit declaration of function 'malloc' [-Wimplicit-function-declaration]
     int* digits = (int*)malloc(digitCount * sizeof(int));
                         ^~~~~~
/in/foo.c:12:25: warning: incompatible implicit declaration of built-in function 'malloc'
/in/foo.c:12:25: note: include '<stdlib.h>' or provide a declaration of 'malloc'
/in/foo.c:25:5: warning: implicit declaration of function 'free' [-Wimplicit-function-declaration]
     free(digits);
     ^~~~
/in/foo.c:25:5: warning: incompatible implicit declaration of built-in function 'free'
/in/foo.c:25:5: note: include '<stdlib.h>' or provide a declaration of 'free'