CB> I would like to know about these, since I've been running 4.0.x on
CB> potato for a very long time now.
While every effort is made upstream to preserve binary compatibility
whenever possible, there have been some issues in the past. For
example, Netscape 4.* and earlier wouldn't run properly with any of
the 3.9.* pre-releases, and XFree86 4.0 was delayed a wee bit due to
this problem. (The 3.9.* implementation was perfectly correct, but
Netscape was doing non-standard things.) A similar issue with a less
critical client might not have been noticed or worked around.
In addition, binary compatibility is one-way only. This means that if
you compile against 4.* and then try to run against 3.3.*, all hell
will break loose. The best-known case is that of Xaw (people notice
due to the ``pretty'' Xaw alternatives, which remain at the 3.3.*
level), but there are also some such issues with Xlib itself (notably
the new support for Unicode, which can be detected at compile time).
This is not to say, of course, that you should not be running the 4.*
X libraries; on the contrary, I am very glad that people do, and I am
very grateful to you, Carl, for making this possible and even easy.
But people who do so should be ready to deal with issues such as the
above. I, for one, am using the CVS libraries on my home machine, but
the stock Debian 3.3.6 libraries at work.
Juliusz
