[sebcat]

> But having to explicitly specify both destination and source sizes might prevented a lot of buffer overwrite bugs.

A good way to prevent this is to have a buffer abstraction, where the size is a property of the type, e.g.,

    typedef struct {
      size_t bytes_used;
      size_t capacity;
      void *data;
    } buf_t;

    int buf_init(buf_t *buf);
    void buf_cleanup(buf_t *buf);
    void buf_copy(buf_t *dst, buf_t *src);
    /* ... */

Of course, it doesn't prevent people from using memcpy directly.