Re: [PATCH] Use "void *" as parameter for functions that are used for aio_set_event_notifier()

[Thomas Huth <thuth@redhat.com>]

On 29/05/2024 20.22, Stefan Hajnoczi wrote:
> On Wed, May 29, 2024 at 07:49:48PM +0200, Thomas Huth wrote:
>> aio_set_event_notifier() and aio_set_event_notifier_poll() in
>> util/aio-posix.c and util/aio-win32.c are casting function pointers of
>> functions that take an "EventNotifier *" pointer as parameter to function
>> pointers that take a "void *" pointer as parameter (i.e. the IOHandler
>> type). When those function pointers are later used to call the referenced
>> function, this triggers undefined behavior errors with the latest version
>> of Clang in Fedora 40 when compiling with the option "-fsanitize=undefined".
>> And this also prevents enabling the strict mode of CFI which is currently
>> disabled with -fsanitize-cfi-icall-generalize-pointers. Thus let us avoid
>> the problem by using "void *" as parameter in all spots where it is needed.
>>
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> ---
>>   Yes, I know, the patch looks ugly ... but I don't see a better way to
>>   tackle this. If someone has a better idea, suggestions are welcome!
> 
> An alternative is adding EventNotifierHandler *io_read, *io_poll_ready,
> *io_poll_begin, and *io_poll_end fields to EventNotifier so that
> aio_set_event_notifier() and aio_set_event_notifier_poll() can pass
> helper functions to the underlying aio_set_fd_handler() and
> aio_set_fd_poll() APIs. These helper functions then invoke the
> EventNotifier callbacks:
> 
> /* Helpers */
> static void event_notifier_io_read(void *opaque)
> {
>      EventNotifier *notifier = opaque;
>      notifier->io_read(notifier);
> }

That's a nice idea, thanks, I'll give it a try!

  Thomas