can _sync_val_compare_and_swap return anything other than int?

问题

I am trying to implement a lock free list. For this project I need and atomic compare and swap instruction that can compare a 32 bit pointer to my 'node' struct.

The node struct is as follows:

 typedef struct node
 {
    int data;
    struct node * next;
    struct node * backlink;
 }node_lf;

I am using _sync_val_compare_and_swap() to perform compare and swap operation. My question is, can this function return a value other than int? This is what I am trying to do:

node_lf cs(node_lf * address, cs_arg *old_val, cs_arg *new_val)
{
    node_lf ptr;
    ptr = (node_lf)__sync_val_compare_and_swap ((int *)address, old_val->node, new_val->node);  
    return (ptr);
}

where cs_arg is another struct to hold the node pointer and other bookkeeping information.

If there are any other methods to implement atomic compare and swap, please suggest.

回答1:

My question is, can this function return a value other than int?

The answer is yes, __sync_val_compare_and_swap can work with types other than int, including char, short, long long and __int128 (on x64).

Note that you may need to cast non-integer types to an appropriately-sized integer for __sync_val_compare_and_swap to work with them.

来源：https://stackoverflow.com/questions/37743658/can-sync-val-compare-and-swap-return-anything-other-than-int