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Date: Tue, 24 Aug 2010 07:33:22 -0600
From: Eric Blake <eblake AT redhat DOT com>
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Subject: Re: Building Emacs-trunk with gcc >= 4.5.1 and libelf installed
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[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.
> [snip]
>> and the following test in 'configure' script is true:
> [snip]
>> 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:
> [snip]
>> 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;
> then
>    ac_have_func=yes
>    AC_DEFINE(SVR4, 1, [Define to 1 on System V Release 4.])
> fi
>
> 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   eblake AT redhat DOT com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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