Compiling with clang generates a handful of warnings and errors

[cheer_xiao]

Hi folks,
I've been compiling the components of Xfce (from the git repository)
with clang. Some compile with just a few warnings, while some fail
(mostly due to memory alignment issues), perhaps most notably exo. Was
Xfce intended to be written in GNU C or ANSI C? If the latter, it
would be beneficial to make sure that Xfce compiles with clang
flawlessly. I know that the wine community have been doing this
extensively.
Regards,
Cheer Xiao
(I'm not a native speaker so please correct my English if it sounds
weird or impolite. Thanks!)