ntdll: Assert when trying to replace an exiting file descriptor in fd_cache.

[Alexandre Julliard]

Sebastian Lackner <sebastian at fds-team.de> writes:

> On 04.03.2015 08:15, Alexandre Julliard wrote:
>> Sebastian Lackner <sebastian at fds-team.de> writes:
>> 
>>> The condition "prev_fd != -1" should never be true. If this is the case then something
>>> is going terrible wrong, and it is better to assert instead of just closing the file
>>> descriptor.
>> 
>> It can happen if the handle was closed on the server side but not yet
>> removed from the cache. Yes, handling of that case is not ideal, but an
>> assert is not an improvement.
>> 
>
> Thanks for taking a look. Hm, from which codepath can it happen that prev_fd != -1?
> The function add_fd_to_cache is only called from server_get_unix_fd, and immediately
> before that there is a call to get_cached_fd. If an fd is cached, then the whole code
> will never be executed (even if its probably the wrong cached file descriptor).
>
> Since its all in an uninterrupted section I also see no other reason why fd_cache
> should change between get_cached_fd and add_fd_to_cache. Could you explain this a bit?
> server_remove_fd_from_cache shouldn't cause any harm, because this function can only
> unset a fd_cache entry.

Actually you are right, this used to be possible, but with the current
code it can't happen.

-- 
Alexandre Julliard
julliard at winehq.org