Hi, AC_PATH_X and friends are unusual in autoconf in that they *explicitly* look into /usr/ for files (see _AC_PATH_X_DIRECT). Notable this is the *only* macro in autoconf that explicitly looks into /usr. To write the logic out in English: iterate through a long list of paths in /usr for a X11/Xlib.h file, and if that exists try a compile test. Then iterate through the same set of paths after s/include/lib/ looking for anything with a library extension (.a .so .sl .dynlib .dll .la) and if one is found try a link test. The big failure case is in cross compilation situations using a sysroot where the target is binary compatible with the host. In this case AC_PATH_X will happily look at /usr and say that yes, X is available, even if the sysroot doesn't have X. My preferred solution would be to delete AC_PATH_X and friends and get everyone to use PKG_CHECK_MODULES(x11), but I can see that isn't a realistic solution. Because the failure case above is a real problem for us, we just delete all of that code. Does anyone have a better solution that would continue to work but not be so dramatically dependent on host assumptions? Cheers, Ross
