[gentoo-dev] RFC: eutils addition - preserve_old_lib

[Jeremy Huddleston]

When the soname of a lib changes between versions of a package, we need
to do a revdep-rebuild --soname <old lib> to make sure all programs that
link against the old lib are rebuilt to use the new one.  In order to
not break currently installed programs, it is best for a package to keep
the old version around until this process is done and the user deletes
the file.  Currently it is up to the individual package maintainers to
do this in their own way.  I've had to do it enough times that I decided
it might be best to just write something into eutils.eclass to handle
it... so...

I'd like to get feedback on the following addition to the eutils.eclass
which I'd like to commit to cvs in the next couple days

+# Jeremy Huddleston <eradicator@g.o>:
+# preserve_old_lib /path/to/libblah.so.0
+# preserve_old_lib_notify /path/to/libblah.so.0
+#
+# These functions are useful when a lib in your package changes
--soname.  Such
+# an example might be from libogg.so.0 to libogg.so.1.  Removing
libogg.so.0
+# would break packages that link against it.  Most people get around
this
+# by using the portage SLOT mechanism, but that is not always a
relevant
+# solution, so instead you can add the following to your ebuilds:
+#
+# src_install() {
+# ...
+# preserve_old_lib /usr/$(get_libdir)/libogg.so.0
+# ...
+# }
+#
+# pkg_postinst() {
+# ...
+# preserve_old_lib_notify /usr/$(get_libdir)/libogg.so.0
+# ...
+# }
+
+preserve_old_lib() {
+       LIB=$1
+
+       if [ -n "${LIB}" -a -f "${ROOT}${LIB}" ]; then
+               SONAME=`basename ${LIB}`
+               DIRNAME=`dirname ${LIB}`
+
+               dodir ${DIRNAME}
+               cp ${ROOT}${LIB} ${D}${DIRNAME}
+               touch ${D}${LIB}
+       fi
+}
+
+preserve_old_lib_notify() {
+        LIB=$1
+
+        if [ -n "${LIB}" -a -f "${ROOT}${LIB}" ]; then
+                SONAME=`basename ${LIB}`
+
+               einfo "An old version of an installed library was
detected on your system."
+               einfo "In order to avoid breaking packages that link
against is, this older version"
+               einfo "is not being removed.  In order to make full use
of this newer version,"
+               einfo "you will need to execute the following command:"
+               einfo "  revdep-rebuild --soname ${SONAME}"
+               einfo
+               einfo "After doing that, you can safely remove ${LIB}"
+        fi
+}
-- 
Jeremy Huddleston <eradicator@g.o>