Implemented stdlib.h

libc/include/stdlib.h

@@ -3,7 +3,28 @@
 
 #include <stddef.h>
 
-void* malloc(const size_t size);
-void free(const void* ptr);
+#define EXIT_SUCCESS 0
+#define EXIT_FAILURE 1
+#define RAND_MAX     0x7FFFFFF
+
+/* Memory allocation */
+void* malloc(size_t size);
+void* calloc(size_t count, size_t size);
+void* realloc(void* ptr, size_t size);
+void free(void* ptr);
+
+/* Process controll */
+void _Exit(int status);
+void exit(int status);
+
+// TODO: move atoi() here
+
+/* Random number generator */
+int rand(void);
+void srand(unsigned int seed);
+
+/* Sort & search */
+void qsort(void* base, size_t nmemb, size_t size, int (*compar)(const void*, const void*));
+void* bsearch(const void* key, const void* base, size_t nmemb, size_t size, int (*compar)(const void*, const void*));
 
 #endif