URL:
<https://savannah.gnu.org/support/?110345>
Summary: AC_PATH_X and friends should not look in
/usr/lib/<various>/include when cross compiling
Project: Autoconf
Submitted by: zackw
Submitted on: Fri 30 Oct 2020 08:46:29 PM UTC
Category: None
Priority: 5 - Normal
Severity: 3 - Normal
Status: Confirmed
Privacy: Public
Assigned to: None
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Operating System: None
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Details:
Reported by Ross Burton on the mailing list:
[Ross:]
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?
[Zack:]
The thing that comes immediately to mind, and which would be feasible
for 2.70, is to not run _AC_PATH_X_DIRECT when cross-compiling. I
don't think it's unreasonable to require people who want to
cross-compile X11 programs to either have the headers and libraries on
the cross-compiler's default search path, or use the --x-includes and
--x-libraries command line switches. It might also make sense for
_AC_PATH_X_XMKMF to look for ${ac_tool_prefix}-xmkmf rather than plain
xmkmf, except I don't know if that would break existing cross compile
build farms.
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