The meaning of these links depends on which list the pool is part of.
They are only the same size class if on the "usedpools" list.
union { pymem_block *_padding;
uint count; } ref; /* number of allocated blocks */
pymem_block *freeblock; /* pool's free list head */
- struct pool_header *nextpool; /* next pool of this size class */
- struct pool_header *prevpool; /* previous pool "" */
+ struct pool_header *nextpool; /* see "Pool table" for meaning */
+ struct pool_header *prevpool; /* " */
uint arenaindex; /* index into arenas of base adr */
uint szidx; /* block size class index */
uint nextoffset; /* bytes to virgin block */