Hmm I think I saw it in a C library

Edit: Might have been this one https://github.com/msteinert/bstring

Edit: actually seems it’s this one. Look at what happens to ystr_header_t https://github.com/Amaury/Ylib/blob/master/src/ystr.c

Another alternative I’ve seen is strings that are not null terminated but where the allocated memory actually begins at ptr[-1] and contains the length of the string. The benefit is that you still get a char array starting at ptr[0].