I think the merged block should be removed from cache bin if it is in there, or it will be alloc twice, is it right?

[dingsp]

fc_malloc/malloc3.cpp

Line 615 in 7a56cf9

cur = cur->merge_next();

[dingsp]

Lucky! it is a double linked list , we can remove it fast.
Since the gc thread is single, we can also remove it safely.