# $Id: Makefile.am,v 1.21 2007/10/15 04:53:59 rocky Exp $ # # Copyright (C) 2003, 2004, 2005, 2006, 2007 Rocky Bernstein # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA # 02110-1301 USA. # ######################################################## # Things to make the libcdio library ######################################################## # # From libtool documentation amended with guidance from N. Boullis: # # 1. Start with version information of `0:0:0' for each libtool library. # # 2. It is probably not a good idea to update the version information # several times between public releases, but rather once per public # release. (This seems to be more an aesthetic consideration than # a hard technical one.) # # 3. If the library source code has changed at all since the last # update, then increment REVISION (`C:R:A' becomes `C:R+1:A'). # # 4. If any interfaces have been added, removed, or changed since the # last update, increment CURRENT, and set REVISION to 0. # # 5. If any interfaces have been added since the last public release, # then increment AGE. # # 6. If any interfaces have been removed or changed since the last # public release, then set AGE to 0. A changed interface means an # incompatibility with previous versions. libcdio_la_CURRENT = 8 libcdio_la_REVISION = 1 libcdio_la_AGE = 1 EXTRA_DIST = image/Makefile FreeBSD/Makefile MSWindows/Makefile \ libcdio.sym noinst_HEADERS = cdio_assert.h cdio_private.h portable.h libcdio_sources = \ _cdio_generic.c \ _cdio_stdio.c \ _cdio_stdio.h \ _cdio_stream.c \ _cdio_stream.h \ aix.c \ bsdi.c \ audio.c \ cd_types.c \ cdio.c \ cdtext.c \ cdtext_private.h \ device.c \ disc.c \ ds.c \ FreeBSD/freebsd.c \ FreeBSD/freebsd.h \ FreeBSD/freebsd_cam.c \ FreeBSD/freebsd_ioctl.c \ generic.h \ gnu_linux.c \ image.h \ image/bincue.c \ image/cdrdao.c \ image_common.c \ image_common.h \ image/nrg.c \ image/nrg.h \ logging.c \ mmc.c \ mmc_private.h \ MSWindows/aspi32.c \ MSWindows/aspi32.h \ MSWindows/win32_ioctl.c \ MSWindows/win32.c \ MSWindows/win32.h \ osx.c \ read.c \ sector.c \ solaris.c \ track.c \ utf8.c \ util.c lib_LTLIBRARIES = libcdio.la libcdio_la_LIBADD = @LIBICONV@ libcdio_la_SOURCES = $(libcdio_sources) libcdio_la_ldflags = -version-info $(libcdio_la_CURRENT):$(libcdio_la_REVISION):$(libcdio_la_AGE) INCLUDES = $(LIBCDIO_CFLAGS) ######################################################## # Things to version the symbols in the libraries ######################################################## # An explanation of the versioning problem from Nicolas Boullis and # the versioned symbol solution he uses below... # # Currently, libvcdinfo uses the cdio_open function from libcdio. # Let's imagine a program foobar that uses both the vcdinfo_open # function from libvcdinfo and the cdio_open function from libcdio. # Currently, libcdio has SONAME libcdio.so.0, libvcdinfo has SONAME # libvcdinfo.so.0 and requires libcdio.so.0, and foobar requires both # libvcdinfo.so.0 and libcdio.so.0. Everything looks fine. # # Now, for some reason, you decide to change the cdio_open function. # That's your right, but you have to bump the CURRENT version and (if I # understand it correctly, athough this is not that clear in libtool's # documentation) set the AGE to 0. Anyway, this bumps the SONAME, which is # sane since the interface changes incompatibly. # Now, you have a new libcdio with SONAME libcdio.so.1. But libvcdinfo and # foobar still require libcdio.so.0. Everything is still fine. # Now, after some minor changes, the author of foobar recompiles foobar. # Then, foobar now requires libvcdinfo.so.0 and libcdio.so.1. And foobar # now segfaults... # What is happening? When you run foobar, if brings both libvcdinfo.so.0 # and libcdio.so.1, but libvcdinfo.so.0 also brings libcdio.so.0. So you # have both libcdio.so.0 and libcdio.so.1 that bring their symbols to the # global namespace. Hence, you have to incompatible versions of the # cdio_open function in the name space. When foobar calls cdio_open, it # may choose the wrong function, and segfaults... # With versioned symbols, the cdio_open function from libcdio.so.0 may be # known as (something that looks like) cdio_open@@CDIO_0. An the cdio_open # function from libcdio.so.1 as cdio_open@@CDIO_1. Both versions of # libcdio would still be brought in by the most recent foobar, but foobar # (and libvcdinfo) know which versioned function to use and then use the # good one. # This is some simple versioning where every symbol is versioned with # something that looks like the SONAME of the library. More complex (and # better) versioning is possible; it is for example what is used by glibc. # But good complex versioning is something that requires much more # work... # The below is a impliments symbol versioning. First of all, I # compute MAJOR as CURENT - AGE; that is what is used within libtool # (at least on GNU/Linux systems) for the number in the SONAME. The # nm command gives the list of symbols known in each of the object # files that will be part of the shared library. And the sed command # extracts from this list those symbols that will be shared. (This sed # command comes from libtool.) libcdio_la_MAJOR = $(shell expr $(libcdio_la_CURRENT) - $(libcdio_la_AGE)) if BUILD_VERSIONED_LIBS libcdio_la_LDFLAGS = $(libcdio_la_ldflags) -Wl,--version-script=libcdio.la.ver libcdio_la_DEPENDENCIES = libcdio.la.ver libcdio.la.ver: $(libcdio_la_OBJECTS) $(srcdir)/libcdio.sym echo 'CDIO_$(libcdio_la_MAJOR) { ' > $@ objs=`for obj in $(libcdio_la_OBJECTS); do sed -ne "s/^pic_object='\(.*\)'$$/\1/p" $$obj; done`; \ if test -n "$${objs}" ; then \ nm $${objs} | sed -n -e 's/^.*[ ][ABCDGIRSTW][ABCDGIRSTW]*[ ][ ]*\([_A-Za-z][_A-Za-z0-9]*\)$$/\1/p' | sort -u | { first=true; while read symbol; do if grep -q "^$${symbol}\$$" $(srcdir)/libcdio.sym; then if test $$first = true; then echo " global:"; first=false; fi; echo " $${symbol};"; fi; done; } >> $@; \ nm $${objs} | sed -n -e 's/^.*[ ][ABCDGIRSTW][ABCDGIRSTW]*[ ][ ]*\([_A-Za-z][_A-Za-z0-9]*\)$$/\1/p' | sort -u | { first=true; while read symbol; do if grep -q "^$${symbol}\$$" $(srcdir)/libcdio.sym; then :; else if test $$first = true; then echo " local:"; first=false; fi; echo " $${symbol};"; fi; done; } >> $@; \ fi echo '};' >> $@ else libcdio_la_LDFLAGS = $(libcdio_la_ldflags) endif MOSTLYCLEANFILES = libcdio.la.ver