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Subject: Re: Building Emacs-trunk with gcc >= 4.5.1 and libelf installed
From: "Yaakov (Cygwin/X)" <yselkowitz AT users DOT sourceforge DOT net>
To: cygwin <cygwin AT cygwin DOT com>, emacs-devel AT gnu DOT org
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Date: Mon, 23 Aug 2010 23:37:11 -0500
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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.

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.

In the meantime, since libelf isn't needed elsewhere in emacs, an easy
workaround is to add "ac_cv_lib_elf_elf_begin=no" to CYGCONF_ARGS.

HTH,


Yaakov



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