> > because you can't increase the size of the structure
> > without bumping the major.
> 
> i see. so, what do you suggest? i want to avoid using malloc here
> and allow the caller to change internal values of the struct.
> 
> should i just write a function to access and modify the various
> values of the struct?

why you want to avoid malloc?

why the caller needs to change values?

YAMAMOTO Takashi