Hi,
given this configure.in (a useless case, but it'll serve as an
example):
== [snip] ====================================
AC_INIT(configure.in)
AC_CONFIG_HEADER(config.h)
if false; then
AC_PATH_XTRA
else
AC_PATH_XTRA
fi
AC_OUTPUT
== [snip] ====================================
..the resulting configure script will fail to define X_DISPLAY_MISSING
on systems without X11.
The reason for this is that AC_PATH_XTRA AC_REQUIREs AC_PATH_X, which
means it will only get expanded for the _first_ AC_PATH_XTRA in the
configure.in above, and then AC_PATH_XTRA uses
test x"$no_x" = xyes
to decide whether or not to define X_DISPLAY_MISSING. But the
AC_PATH_X code will never be executed for the second AC_PATH_XTRA
above, so $no_x will never be set to anything at all.
(Autoconf's X11 checking is in general a mess, BTW.)
Regards,
Morten
