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

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

[Angelo Graziosi]

Trying to build Emacs-trunk on Cygwin with GCC >= 4.5.1, I have found a 
problem if also the package 'libelf0' is installed.

The build fails in this way:

=====================================
./configure
[...]
checking for elf_begin in -lelf... yes
[...]
make
[...]
gcc-4.6...
In file included from /usr/include/X11/Xos.h:146:0,
                  from /tmp/emacs/src/xfaces.c:277:
/usr/include/X11/Xarch.h:43:30: fatal error: sys/byteorder.h: No such
file or directory
compilation terminated.
make[2]: *** [xfaces.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[2]: Leaving directory '/tmp/emacs/Work/src'
make[1]: *** [src] Error 2
make[1]: Leaving directory '/tmp/emacs/Work'
make: *** [bootstrap] Error 2
=====================================

The issue is fixed, simply, if I uninstall 'libelf0'. Indeed...

If 'libelf0' is installed, we have from 'configure',

--------
checking for elf_begin in -lelf... yes
--------

and the following test in 'configure' script is true:

--------
if test $ac_have_func = no && test "$ac_cv_lib_elf_elf_begin" = yes; then
   ac_have_func=yes

$as_echo "#define SVR4 1" >>confdefs.h

fi
--------

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:

--------
[...]
#  if defined(SVR4) || defined(__SVR4)
#   include <sys/byteorder.h>
#  elif
[...]
--------

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.

What does the Cygwin 'libelf0' maintainer think about these facts?

Thanks,
Angelo.

---
[1] Here Cygwin isn't different frome GNU/Linux Kubuntu 10.04. :-)

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

[Yaakov (Cygwin/X)]

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

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

[Angelo Graziosi]

Yaakov ,
thanks for clarifications and suggestions. I hope someone on the Emacs 
list can recipie and apply them appropriately.

Emacs guys,
the simplest workaround I found to fix the issue was to add

#undef SVR4

in src/s/cygwin.h

Thanks,
Angelo.


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.
>
> 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.

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

[Yaakov (Cygwin/X)]

On Tue, 2010-08-24 at 11:05 +0200, Angelo Graziosi wrote:
> Yaakov ,
> thanks for clarifications and suggestions. I hope someone on the Emacs 
> list can recipie and apply them appropriately.

This is not an issue with emacs per se but with autoconf, so this needs
to be fixed there.  Eric?


Yaakov
Cygwin/X