C dynamic structure

Something I've been wondering,

Is it possible at runtime to dynamically create a struct? I don't mean dynamic array size, I mean the variables and such inside a structure.

>>6
Black magic is best magic. I bet you can pull of some wizardry with an array of dynamically-sized arrays, each of which represents an object, using an hash table to identify each sub-array. The type of a variable can be encoded into the last few bits of every variable in each sub-array.

It probably won't work very well, but it sounds fun.