This is with 4.12.1: When the window-list-on-middle-click option is enabled, Xfdesktop receives a segmentation fault when a middle-click is attempted.
We need the backtrace of the crash. Please follow the instructions of the following link: http://docs.xfce.org/contribute/bugs/start#backtraces
Created attachment 6117 backtrace Ok, it appears to be related to the compiler used. icc is problematic, gcc works. Feel free to close this as invalid if icc is not supported.
Unless this is truely a bug in xfdesktop, we can't do much about it. If this is a bug, it could be only exposed by on compiler and not the other. How ever this part of the code looks straight forward. It gets an icon from wnck_window_get_mini_icon possebly scales it gdk_pixbuf_scale_simple or copies it gdk_pixbuf_copy and then calls gdk_pixbuf_saturate_and_pixelate where it crashes. In case it has anything to do with the application it would be that there is a NULL pointer in there. If libwnck and gdk-pixbuf are compiled with the default checks it should tell you in the console output and not crash. If it is a compiler problem it could be either a bug in the compiler giving a wrong argument to the function. or the fact that you are mixing compilers. The application binary interface (ABI) of C code is specified but there are multiple (depening on the platform and such) if gdk-pixbuf is compiled with gcc and xfdesktop with icc, there is a slight posibility that they use a different calling ABI. If we want to look deeper into this, I suggest writing a simple application that does just menu_item_from_wnck_window and see if that causes the crash as well.
It is possible that this is a compiler bug. However, I've been using icc for ages and never had trouble with middle-clicking before. I'm not really interested in debugging compilers however. Since gcc works, I'll be using that from now on. But thanks for having a look at it!