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AC_PATH_X and friends explicitly look into /usr/lib
From: |
Ross Burton |
Subject: |
AC_PATH_X and friends explicitly look into /usr/lib |
Date: |
Thu, 15 Oct 2020 14:38:52 +0100 |
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
- AC_PATH_X and friends explicitly look into /usr/lib,
Ross Burton <=