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Re: Building Emacs-trunk with gcc >= 4.5.1 and libelf installed

From: Eric Blake
Subject: Re: Building Emacs-trunk with gcc >= 4.5.1 and libelf installed
Date: Tue, 24 Aug 2010 07:33:22 -0600
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100806 Fedora/3.1.2-1.fc13 Mnenhy/0.8.3 Thunderbird/3.1.2

[adding autoconf and gnulib; replies can drop cygwin]

On 08/23/2010 10:37 PM, Yaakov (Cygwin/X) wrote:
On Tue, 2010-08-24 at 01:31 +0200, Angelo Graziosi wrote:
Trying to build Emacs-trunk on Cygwin with GCC>= 4.5.1, I have found a
problem if also the package 'libelf0' is installed.
and the following test in 'configure' script is true:
i.e. SVR4 is _defined_. But... 'src/xfaces.c' includes indirectly via
'/usr/include/X11/Xos.h' the header '/usr/include/X11/Xarch.h', which has:
i.e. finding SVR4 defined, it searches for 'byteorder.h' in
'/usr/include/sys' and not in '/usr/include/asm', where it lives (*as on
GNU/Linux*[1]), and this leads to the above failure.

This is coming from autoconf's AC_FUNC_GETLOADAVG, which tries to find
several different getloadavg(3) implementations (which Cygwin doesn't
provide), otherwise it points to an AC_LIBOBJ from gnulib.  On Solaris,
the gnulib getloadavg uses kvm_open(3) and friends, and libkvm requires
libelf, hence the check for the latter.

According to gnulib, AC_FUNC_GETLOADAVG is obsolescent (in part because it uses AC_LIBOBJ in a manner that is not easily extensible by gnulib). If emacs is using modern gnulib, then it is _not_ using AC_FUNC_GETLOADAVG from autoconf, but rather the more up-to-date gl_GETLOADAVG from the gnulib module getloadavg.

Either way:

AFAICS the proper solution is, in _AC_LIBOBJ_GETLOADAVG:

if test $ac_have_func = no&&  test "$ac_cv_lib_elf_elf_begin" = yes;
   AC_DEFINE(SVR4, 1, [Define to 1 on System V Release 4.])

to add<<  &&  test "$ac_cv_lib_kvm_kvm_open" = yes>>  to the conditional.

Yes, autoconf's AC_FUNC_GETLOADAVG should be updated in this manner, and that should also be reflected into gnulib's gl_GETLOADAVG. Thanks for the analysis.

Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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