/in/foo.c: In function 'concatAndRepeat':
/in/foo.c:7:25: warning: implicit declaration of function 'malloc' [-Wimplicit-function-declaration]
     char* newA = (char*)malloc((lenA + lenB + 1) * sizeof(char));
                         ^~~~~~
/in/foo.c:7:25: warning: incompatible implicit declaration of built-in function 'malloc'
/in/foo.c:7:25: note: include '<stdlib.h>' or provide a declaration of 'malloc'
/in/foo.c:17:5: warning: implicit declaration of function 'free' [-Wimplicit-function-declaration]
     free(newB);
     ^~~~
/in/foo.c:17:5: warning: incompatible implicit declaration of built-in function 'free'
/in/foo.c:17:5: note: include '<stdlib.h>' or provide a declaration of 'free'
/in/foo.c: In function 'main':
/in/foo.c:31:5: warning: incompatible implicit declaration of built-in function 'free'
     free(result);
     ^~~~
/in/foo.c:31:5: note: include '<stdlib.h>' or provide a declaration of 'free'