> For example, removing a prefix the C way would be to add the size of the prefix to the pointer.
Surely to do this you'd still have to keep either a reference to the original pointer around or remember the offset so you could `free(str)` with the correct pointer?
Yes, although it's not always your responsibility to do that.
Firstly not all strings are on the heap, but ignoring that... If somebody passes you a pointer to a string and you aren't going to hold onto it for a while, you can just add to the pointer and it's no big deal. But yes, if you own the allocation, you need to keep the old pointer too.
Surely to do this you'd still have to keep either a reference to the original pointer around or remember the offset so you could `free(str)` with the correct pointer?