/in/foo.c: In function 'main':
/in/foo.c:6:13: warning: implicit declaration of function 'malloc' [-Wimplicit-function-declaration]
  a = (int *)malloc(x * sizeof(int));
             ^~~~~~
/in/foo.c:6:13: warning: incompatible implicit declaration of built-in function 'malloc'
/in/foo.c:6:13: note: include '<stdlib.h>' or provide a declaration of 'malloc'
/in/foo.c:33:4: warning: implicit declaration of function 'free' [-Wimplicit-function-declaration]
    free(temp);
    ^~~~
/in/foo.c:33:4: warning: incompatible implicit declaration of built-in function 'free'
/in/foo.c:33:4: note: include '<stdlib.h>' or provide a declaration of 'free'
/in/foo.c:59:4: warning: incompatible implicit declaration of built-in function 'free'
    free(temp);
    ^~~~
/in/foo.c:59:4: note: include '<stdlib.h>' or provide a declaration of 'free'
/in/foo.c:66:2: warning: implicit declaration of function 'system' [-Wimplicit-function-declaration]
  system("pause");
  ^~~~~~