method for altering installation location

[Eric Blake]

How does one properly make a build system install to the
system-preferred locations for 64-bit binaries? I'm wondering how to
properly make my build system choose "/usr/lib64" over simply "/usr/lib"
when configure is run. I know this can be done simply via
"--prefix=/usr --libdir=lib64", and maybe this is what it should be

Yes, that IS the preferred way (although autoconf's config.site can make
it easier). Your configure script should not hard code any knowledge,
rather the user of your configure script should supply their knowledge.

It's also recommended that you convince your distro to install a
/usr/share/config.site file, which is the easiest way to get
'./configure --prefix=/usr' to just do the right things for all the
other variables. Fedora has already done so:

$ rpm -qf /usr/share/config.site
autoconf-2.69-20.fc22.noarch
$ cat /usr/share/config.site
# This is the config.site file to satisfy FHS defaults when installing below
# /usr.
#
# You may override this file by your config.site using the CONFIG_SITE env
# variable.
#
# Note: This file includes also RHEL/Fedora fix for installing libraries
into
# "/lib/lib64" on 64bit systems.

if test -n "$host"; then
# skip when cross-compiling
return 0
fi

if test "$prefix" = /usr \
|| { test "$prefix" = NONE && test "$ac_default_prefix" = /usr ; }
then
test "$sysconfdir" = '${prefix}/etc' && sysconfdir=/etc
test "$sharedstatedir" = '${prefix}/com' && sharedstatedir=/var
test "$localstatedir" = '${prefix}/var' && localstatedir=/var

ARCH=`uname -m`
for i in x86_64 ppc64 s390x aarch64; do
if test $ARCH = $i; then
test "$libdir" = '${exec_prefix}/lib' &&
libdir='${exec_prefix}/lib64'
break
fi
done
fi

(along with some type of bootstrap script). I was just wondering if
there are already elegant/"smiled upon" methods for doing this in
configure (i.e. configure.ac).

There's nothing for you to do in configure.ac (that doesn't scale -
you'd have to modify every packages' configure.ac to get them to all act
the same). Rather, the work should be done by whoever wants
installation of things into /usr to just work.

See also the autoconf manual:
https://www.gnu.org/software/autoconf/manual/autoconf.html#Site-Defaults

[Michael Felt]

I have seen a lot of solutions where .../lib/files.extension is used for
32-bit and .../lib64/files.extension or .../lib/64/files.extension.

I am undecided about what I prefer of these two.

However, as my focus is AIX - I will prefer to use only one directory and
the same file (archive) name and even same member names - and utilize an
AIX feature that permits the same member name for both 32 and 64 bit - as
the linker/loader will only dlopen one, depending on the mode of the
application.

This does complicate the final packaging - but I am hoping to resolve/solve
that outside of the GNU autotools. Instead, I will make the 32-bit library
a pre-requisite and add the glue to include/copy the 64-bit members into
the existing 32-bit archive.

For packaging Linux distros I would look at what seems to be the convention
- and try to follow that.

Post by Eric Blake

How does one properly make a build system install to the
system-preferred locations for 64-bit binaries? I'm wondering how to
properly make my build system choose "/usr/lib64" over simply "/usr/lib"
when configure is run. I know this can be done simply via
"--prefix=/usr --libdir=lib64", and maybe this is what it should be

Yes, that IS the preferred way (although autoconf's config.site can make
it easier). Your configure script should not hard code any knowledge,
rather the user of your configure script should supply their knowledge.
It's also recommended that you convince your distro to install a
/usr/share/config.site file, which is the easiest way to get
'./configure --prefix=/usr' to just do the right things for all the
$ rpm -qf /usr/share/config.site
autoconf-2.69-20.fc22.noarch
$ cat /usr/share/config.site
# This is the config.site file to satisfy FHS defaults when installing below
# /usr.
#
# You may override this file by your config.site using the CONFIG_SITE env
# variable.
#
# Note: This file includes also RHEL/Fedora fix for installing libraries
into
# "/lib/lib64" on 64bit systems.
if test -n "$host"; then
# skip when cross-compiling
return 0
fi
if test "$prefix" = /usr \
|| { test "$prefix" = NONE && test "$ac_default_prefix" = /usr ; }
then
test "$sysconfdir" = '${prefix}/etc' && sysconfdir=/etc
test "$sharedstatedir" = '${prefix}/com' && sharedstatedir=/var
test "$localstatedir" = '${prefix}/var' && localstatedir=/var
ARCH=`uname -m`
for i in x86_64 ppc64 s390x aarch64; do
if test $ARCH = $i; then
test "$libdir" = '${exec_prefix}/lib' &&
libdir='${exec_prefix}/lib64'
break
fi
done
fi

(along with some type of bootstrap script). I was just wondering if
there are already elegant/"smiled upon" methods for doing this in
configure (i.e. configure.ac).

There's nothing for you to do in configure.ac (that doesn't scale -
you'd have to modify every packages' configure.ac to get them to all act
the same). Rather, the work should be done by whoever wants
installation of things into /usr to just work.
https://www.gnu.org/software/autoconf/manual/autoconf.html#Site-Defaults
--
Eric Blake eblake redhat com [phone]
Libvirt virtualization library http://libvirt.org