The following functions are declared in the skalibs/genalloc.h header, and implemented in the libskarnet.a or libskarnet.so library.
genalloc is the skalibs way of handling dynamic arrays, i.e. dynamically growing arrays of fixed-size objects. Any array that needs to be stored in heap memory can be implemented via genalloc.
Most genalloc functions are just macro calls around stralloc functions.
The genalloc.h header is actually very simple and the prototypes there are self-explaining.