(debian/testing | intel 32bit | xfwm4 4.11.2git)

After updating my build from git master, I found several broken behaviours (although wm is not crashing). I did a git bisect, and found the guilty commit to be "Use 32 unsigned integer for opacity" http://git.xfce.org/xfce/xfwm4/commit/?id=b3b014a3ae58efe9b4eecdc9bd75316eb552e7c1

After some experimentation I found this part of the commit to be causing the problem:
(hints.c line 245)
-    *value = *((long *) data) & 0xffffffff;
+    *value = *((long *) data) & ((1L << real_format) - 1);

That mask on the right evaluates correctly only when real_format < 32. Using ((1LL << real_format) - 1) ensures enough width, and then xfwm4 runs okay.

The similar mask on line 510 hasn't caused problems, but may need attention.