It's a relatively common pattern to have a "collection" data structure (like a list or hash table) use link structs embedded inside other structs to simplify me

It's a relatively common pattern to have a "collection" data structure (like a list or hash table) use link structs embedded inside other structs to simplify memory management. When you append to a linked list in Java, you always allocate a new Link object and then update the various pointers. Using this pattern in C, the object you want to put in a list contains a list_link_t structure, and the list library takes as arguments pointers to these structures. This may sound like an argument about convenience, but the implications of this are very significant: if you have to allocate memory, the operation can fail. So in the C version (unlike the Java one) you can control exactly in which contexts something can fail. For example, if you want to trigger some operation after some number of second elapses, you can preallocate some structure and then just populate it and fill it in when the timeout fires. Timeouts are usually just signals or other contexts where you have no way to return failure, so it's important that it be possible to always handle that case correctly without the possibility of failing.