Portable programs that want to perform atomic file locking using a
lockfile,and need to avoid reliance on NFS support for O_EXCL,can
create a unique file on the same file system (e.g.,incorporating
hostname and PID),and use link(2) to make a link to the lockfile. If
link(2) returns 0,the lock is successful. Otherwise,use stat(2) on
the unique file to check if its link count has increased to 2,in
which case the lock is also successful.

这似乎工作得很好,但是为了在我的测试中获得100％的代码覆盖率,我需要覆盖链接数增加到2的情况.

我已经尝试过谷歌搜索了,但我似乎能找到的所有内容都是上面反复出现的“它完成的方式”.

任何人都可以向我解释一下哪种情况会导致链接失败(返回-1),但链接数增加到2？