+#include <stddef.h>
+
+#define abs(x) __builtin_abs(x)
+
+int atoi(const char *str);
+long atol(const char *str);
+long strtol(const char *str, char **endp, int base);
+
+void itoa(int val, char *buf, int base);
+void utoa(unsigned int val, char *buf, int base);
+
+void qsort(void *arr, size_t count, size_t size, int (*cmp)(const void*, const void*));
+
+/* defined in malloc.c */
+void *malloc(size_t sz);
+void *calloc(size_t num, size_t sz);
+void *realloc(void *ptr, size_t sz);
+void free(void *ptr);