[PATCH] Fix write to uninitialized bytes for XCB event

[Enrico Forestieri]

On Sun, Feb 23, 2020 at 12:04:20PM -0500, Scott Kostyshak wrote:
> On Sun, Feb 23, 2020 at 03:10:37PM +0100, Enrico Forestieri wrote:
> > On Sun, Feb 23, 2020 at 08:22:55AM -0500, Scott Kostyshak wrote:
> > > On Wed, Feb 19, 2020 at 08:07:46PM +0100, Enrico Forestieri wrote:
> > > > On Wed, Feb 19, 2020 at 01:19:54PM -0500, Scott Kostyshak wrote:
> > > > > 
> > > > > It seems I committed too soon. Sorry for not waiting. Both the macro
> > > > > approach and Enrico's proposal are cleaner than my approach. I was
> > > > > planning to pursue the macro approach in a follow-up commit.
> > > > 
> > > > Apparently, the macro approach was abandoned by the Qt folks.
> > > > 
> > > > > Regarding
> > > > > C++11, don't we already use range-based for loops? Or is the question
> > > > > about if we require *all* of C++11?
> > > > 
> > > > The latter. As shown by Pavel in the other post gcc 4.7 is lacking
> > > > something. As we use xcb_selection_notify_event_t only in one place,
> > > > I think defining a macro is overkill. In order to avoid many calls
> > > > to calloc() (I don't know how memory fragmentation is dealt with by
> > > > modern compilers), we could anyway use that idea as follows:
> > > > 
> > > > 	union {
> > > > 		xcb_selection_notify_event_t event;
> > > > 		char padding[32];
> > > > 	} padded_event;
> > > > 	auto & nev = padded_event.event;
> > > 
> > > Enrico, I propose that you commit. Thanks for the fix.
> > 
> > According to the followups to the post by Pavel and commit 748bb5a0,
> > I think that the C++11 alignas solution is preferred. Given that you
> > can check its effectiveness, I think that it is better that you
> > commit it.
> 
> I tried to test but probably I'm missing something in the change that I
> tested since I still get the following with Valgrind:

Please, can you also try with the union approach above?

-- 
Enrico