From: Enrico Forestieri <forenr@lyx.org>
Date: Tue, 25 Feb 2020 11:37:51 +0000 (+0100)
Subject: Cleaner fix to ensure 32-bit XCB events
X-Git-Tag: lyx-2.4.0dev-acb2ca7b~1214
X-Git-Url: https://git.lyx.org/gitweb/?a=commitdiff_plain;h=f28334ac8bfb4b720c27516038ae89926bbf6258;p=features.git

Cleaner fix to ensure 32-bit XCB events

This fix still satisfies Valgrind and is cleaner than the approach
at 19c41bd0: instead of using calloc we now use the C++11 specifier
alignas. For more info, see the following ML thread:
https://www.mail-archive.com/search?l=mid&q=20200219024908.5n4x4osni55gylo3%40tallinn
---

diff --git a/src/frontends/qt/GuiApplication.cpp b/src/frontends/qt/GuiApplication.cpp
index 8fdd9bf99d..573ebb905f 100644
--- a/src/frontends/qt/GuiApplication.cpp
+++ b/src/frontends/qt/GuiApplication.cpp
@@ -3352,7 +3352,13 @@ bool GuiApplication::nativeEventFilter(const QByteArray & eventType,
 				// not doing that, maybe because of our
 				// "persistent selection" implementation
 				// (see comments in GuiSelection.cpp).
-				xcb_selection_notify_event_t nev;
+				// It is expected that every X11 event is
+				// 32 bytes long, even if not all 32 bytes are
+				// needed. See:
+				// https://www.x.org/releases/current/doc/man/man3/xcb_send_event.3.xhtml
+				struct alignas(32) padded_event
+					: xcb_selection_notify_event_t {};
+				padded_event nev = {};
 				nev.response_type = XCB_SELECTION_NOTIFY;
 				nev.requestor = srev->requestor;
 				nev.selection = srev->selection;