QPluginLoader/ELF: fix Clang ASan builds

Clang aligns the object at 32-byte boundaries even though we
specifically asked for alignof(void*), so tell it not to sanitize the
address of the plugin object. Tested with Clang 12 and 13.

GCC seems not to be affected, even when ASan is enabled.

If this doesn't work, we may need to accept reading a note that is
improperly aligned. I don't think the output will be actually a correct
note because the intra-note alignment will be wrong (I carefully chose
the ELF note name so it would not require alignment, but that's only
valid up to 8-byte alignments).

Fixes: QTBUG-97941
Change-Id: Ice04365c72984d07a64dfffd16b422fe074d8a70
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 3 insertions, 1 deletions

diff --git a/tests/auto/corelib/plugin/qpluginloader/fakeplugin.cpp b/tests/auto/corelib/plugin/qpluginloader/fakeplugin.cpp
index 6d758f23c9..c1b939bf3e 100644
--- a/tests/auto/corelib/plugin/qpluginloader/fakeplugin.cpp
+++ b/tests/auto/corelib/plugin/qpluginloader/fakeplugin.cpp
@@ -50,7 +50,9 @@ static constexpr bool IsDebug = false;
 #endif
 
 #if defined(__ELF__) && PLUGIN_VERSION >= 1
-__attribute__((section(".note.qt.metadata"), used, aligned(4)))
+// GCC will produce:
+// fakeplugin.cpp:64:3: warning: ‘no_sanitize_address’ attribute ignored [-Wattributes]
+__attribute__((section(".note.qt.metadata"), used, no_sanitize("address"), aligned(sizeof(void*))))
 static const struct {
     unsigned n_namesz = sizeof(name);
     unsigned n_descsz = sizeof(payload);