display-test: Fix a race condition in test suite

Several tests in this suite use setting and checking client.display_stopped (in
test-compositor.h) to synchronise between threads. This is a data race because
display_stopped is a non-atomic int. Fix this by making it an atomic_bool
instead. We don't need to change the access code because reads and writes are
sequentially consistent by default.

This can be reproduced (with both clang and gcc) by running
```
meson -Db_sanitize=thread build
cd build
ninja
meson test
```

Signed-off-by: Fergus Dall <sidereal@google.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/tests/test-compositor.h b/tests/test-compositor.h
index f763fef..7b350fe 100644
--- a/tests/test-compositor.h
+++ b/tests/test-compositor.h
@@ -25,6 +25,7 @@
 
 #include <stdint.h>
 #include <unistd.h>
+#include <stdatomic.h>
 
 #include "wayland-server.h"
 #include "wayland-client.h"
@@ -65,7 +66,7 @@ struct client {
 	struct wl_display *wl_display;
 	struct test_compositor *tc;
 
-	int display_stopped;
+	atomic_bool display_stopped;
 };
 
 struct client *client_connect(void);