Comment by 8organicbits

In the past I've taken inspiration from strncpy: the caller needs to allocate the memory. For the email example, you'd probably also want a function to tell you the length of the emailstring, but for other types there are clear size limits. This puts the caller in control of memory allocation, so they may be able to statically allocate, allocate in an arena, or use other methods which promote performance. The static approach is really nice when it works, because there's nothing to free.