stack_block
struct stack_block *prev;
#define SPACE(sp) ((char*)(sp) + ALIGN(sizeof(struct stack_block)))
static struct stack_block *stackp;
struct stack_block *sp;
allocsize = ALIGN(sizeof(struct stack_block)) + ALIGN(nbytes);
struct stack_block *sp;
struct stack_block *sp;
struct stack_block *oldstackp;
INT_MAX / 2 - ALIGN(sizeof(struct stack_block)))
min += ALIGN(sizeof(struct stack_block));
newlen -= ALIGN(sizeof(struct stack_block));
struct stack_block *stackp;