ARENA_RUN_MAGIC
assert(run->magic == ARENA_RUN_MAGIC);
assert(run->magic == ARENA_RUN_MAGIC);
run->magic = ARENA_RUN_MAGIC;
assert(run->magic == ARENA_RUN_MAGIC);
assert(bin->runcur->magic == ARENA_RUN_MAGIC);
assert(run->magic == ARENA_RUN_MAGIC);
assert(run->magic == ARENA_RUN_MAGIC);