Upstream is here:
https://bugs.freedesktop.org/show_bug.cgi?id=18451

Upstream-status: Backport

Signed-off-by: Christopher Hallinan <challinan (a] gmail.com>

diff --git a/Xext/xace.c b/Xext/xace.c
index e10d837..c757cad 100644
--- a/Xext/xace.c
+++ b/Xext/xace.c
@@ -87,7 +87,18 @@ void XaceHookAuditEnd(ClientPtr ptr, int result)
  */
 int XaceHook(int hook, ...)
 {
-    pointer calldata;	/* data passed to callback */
+    union {
+	XaceResourceAccessRec res;
+	XaceDeviceAccessRec dev;
+	XaceSendAccessRec send;
+	XaceReceiveAccessRec recv;
+	XaceClientAccessRec client;
+	XaceExtAccessRec ext;
+	XaceServerAccessRec server;
+	XaceScreenAccessRec screen;
+	XaceAuthAvailRec auth;
+	XaceKeyAvailRec key;
+    } u;
     int *prv = NULL;	/* points to return value from callback */
     va_list ap;		/* argument list */
     va_start(ap, hook);
@@ -99,117 +110,86 @@ int XaceHook(int hook, ...)
      */
     switch (hook)
     {
-	case XACE_RESOURCE_ACCESS: {
-	    XaceResourceAccessRec rec;
-	    rec.client = va_arg(ap, ClientPtr);
-	    rec.id = va_arg(ap, XID);
-	    rec.rtype = va_arg(ap, RESTYPE);
-	    rec.res = va_arg(ap, pointer);
-	    rec.ptype = va_arg(ap, RESTYPE);
-	    rec.parent = va_arg(ap, pointer);
-	    rec.access_mode = va_arg(ap, Mask);
-	    rec.status = Success; /* default allow */
-	    calldata = &rec;
-	    prv = &rec.status;
+	case XACE_RESOURCE_ACCESS:
+	    u.res.client = va_arg(ap, ClientPtr);
+	    u.res.id = va_arg(ap, XID);
+	    u.res.rtype = va_arg(ap, RESTYPE);
+	    u.res.res = va_arg(ap, pointer);
+	    u.res.ptype = va_arg(ap, RESTYPE);
+	    u.res.parent = va_arg(ap, pointer);
+	    u.res.access_mode = va_arg(ap, Mask);
+	    u.res.status = Success; /* default allow */
+	    prv = &u.res.status;
 	    break;
-	}
-	case XACE_DEVICE_ACCESS: {
-	    XaceDeviceAccessRec rec;
-	    rec.client = va_arg(ap, ClientPtr);
-	    rec.dev = va_arg(ap, DeviceIntPtr);
-	    rec.access_mode = va_arg(ap, Mask);
-	    rec.status = Success; /* default allow */
-	    calldata = &rec;
-	    prv = &rec.status;
+	case XACE_DEVICE_ACCESS:
+	    u.dev.client = va_arg(ap, ClientPtr);
+	    u.dev.dev = va_arg(ap, DeviceIntPtr);
+	    u.dev.access_mode = va_arg(ap, Mask);
+	    u.dev.status = Success; /* default allow */
+	    prv = &u.dev.status;
 	    break;
-	}
-	case XACE_SEND_ACCESS: {
-	    XaceSendAccessRec rec;
-	    rec.client = va_arg(ap, ClientPtr);
-	    rec.dev = va_arg(ap, DeviceIntPtr);
-	    rec.pWin = va_arg(ap, WindowPtr);
-	    rec.events = va_arg(ap, xEventPtr);
-	    rec.count = va_arg(ap, int);
-	    rec.status = Success; /* default allow */
-	    calldata = &rec;
-	    prv = &rec.status;
+	case XACE_SEND_ACCESS:
+	    u.send.client = va_arg(ap, ClientPtr);
+	    u.send.dev = va_arg(ap, DeviceIntPtr);
+	    u.send.pWin = va_arg(ap, WindowPtr);
+	    u.send.events = va_arg(ap, xEventPtr);
+	    u.send.count = va_arg(ap, int);
+	    u.send.status = Success; /* default allow */
+	    prv = &u.send.status;
 	    break;
-	}
-	case XACE_RECEIVE_ACCESS: {
-	    XaceReceiveAccessRec rec;
-	    rec.client = va_arg(ap, ClientPtr);
-	    rec.pWin = va_arg(ap, WindowPtr);
-	    rec.events = va_arg(ap, xEventPtr);
-	    rec.count = va_arg(ap, int);
-	    rec.status = Success; /* default allow */
-	    calldata = &rec;
-	    prv = &rec.status;
+	case XACE_RECEIVE_ACCESS:
+	    u.recv.client = va_arg(ap, ClientPtr);
+	    u.recv.pWin = va_arg(ap, WindowPtr);
+	    u.recv.events = va_arg(ap, xEventPtr);
+	    u.recv.count = va_arg(ap, int);
+	    u.recv.status = Success; /* default allow */
+	    prv = &u.recv.status;
 	    break;
-	}
-	case XACE_CLIENT_ACCESS: {
-	    XaceClientAccessRec rec;
-	    rec.client = va_arg(ap, ClientPtr);
-	    rec.target = va_arg(ap, ClientPtr);
-	    rec.access_mode = va_arg(ap, Mask);
-	    rec.status = Success; /* default allow */
-	    calldata = &rec;
-	    prv = &rec.status;
+	case XACE_CLIENT_ACCESS:
+	    u.client.client = va_arg(ap, ClientPtr);
+	    u.client.target = va_arg(ap, ClientPtr);
+	    u.client.access_mode = va_arg(ap, Mask);
+	    u.client.status = Success; /* default allow */
+	    prv = &u.client.status;
 	    break;
-	}
-	case XACE_EXT_ACCESS: {
-	    XaceExtAccessRec rec;
-	    rec.client = va_arg(ap, ClientPtr);
-	    rec.ext = va_arg(ap, ExtensionEntry*);
-	    rec.access_mode = DixGetAttrAccess;
-	    rec.status = Success; /* default allow */
-	    calldata = &rec;
-	    prv = &rec.status;
+	case XACE_EXT_ACCESS:
+	    u.ext.client = va_arg(ap, ClientPtr);
+	    u.ext.ext = va_arg(ap, ExtensionEntry*);
+	    u.ext.access_mode = DixGetAttrAccess;
+	    u.ext.status = Success; /* default allow */
+	    prv = &u.ext.status;
 	    break;
-	}
-	case XACE_SERVER_ACCESS: {
-	    XaceServerAccessRec rec;
-	    rec.client = va_arg(ap, ClientPtr);
-	    rec.access_mode = va_arg(ap, Mask);
-	    rec.status = Success; /* default allow */
-	    calldata = &rec;
-	    prv = &rec.status;
+	case XACE_SERVER_ACCESS:
+	    u.server.client = va_arg(ap, ClientPtr);
+	    u.server.access_mode = va_arg(ap, Mask);
+	    u.server.status = Success; /* default allow */
+	    prv = &u.server.status;
 	    break;
-	}
 	case XACE_SCREEN_ACCESS:
-	case XACE_SCREENSAVER_ACCESS: {
-	    XaceScreenAccessRec rec;
-	    rec.client = va_arg(ap, ClientPtr);
-	    rec.screen = va_arg(ap, ScreenPtr);
-	    rec.access_mode = va_arg(ap, Mask);
-	    rec.status = Success; /* default allow */
-	    calldata = &rec;
-	    prv = &rec.status;
+	case XACE_SCREENSAVER_ACCESS:
+	    u.screen.client = va_arg(ap, ClientPtr);
+	    u.screen.screen = va_arg(ap, ScreenPtr);
+	    u.screen.access_mode = va_arg(ap, Mask);
+	    u.screen.status = Success; /* default allow */
+	    prv = &u.screen.status;
 	    break;
-	}
-	case XACE_AUTH_AVAIL: {
-	    XaceAuthAvailRec rec;
-	    rec.client = va_arg(ap, ClientPtr);
-	    rec.authId = va_arg(ap, XID);
-	    calldata = &rec;
+	case XACE_AUTH_AVAIL:
+	    u.auth.client = va_arg(ap, ClientPtr);
+	    u.auth.authId = va_arg(ap, XID);
 	    break;
-	}
-	case XACE_KEY_AVAIL: {
-	    XaceKeyAvailRec rec;
-	    rec.event = va_arg(ap, xEventPtr);
-	    rec.keybd = va_arg(ap, DeviceIntPtr);
-	    rec.count = va_arg(ap, int);
-	    calldata = &rec;
+	case XACE_KEY_AVAIL:
+	    u.key.event = va_arg(ap, xEventPtr);
+	    u.key.keybd = va_arg(ap, DeviceIntPtr);
+	    u.key.count = va_arg(ap, int);
 	    break;
-	}
-	default: {
+	default:
 	    va_end(ap);
 	    return 0;	/* unimplemented hook number */
-	}
     }
     va_end(ap);
  
     /* call callbacks and return result, if any. */
-    CallCallbacks(&XaceHooks[hook], calldata);
+    CallCallbacks(&XaceHooks[hook], &u);
     return prv ? *prv : Success;
 }