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# Copyright (C) 2003-2010, 2012-2013, 2017
# Rocky Bernstein <rocky@gnu.org>
#
# 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 3 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, see <http://www.gnu.org/licenses/>.
########################################################
# 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 = 19
libcdio_la_REVISION = 0
libcdio_la_AGE = 0
EXTRA_DIST = image/Makefile \
mmc/Makefile \
FreeBSD/Makefile MSWindows/Makefile \
libcdio.sym
noinst_HEADERS = cdio_assert.h cdio_private.h filemode.h portable.h
libcdio_sources = \
_cdio_generic.c \
_cdio_stdio.c \
_cdio_stdio.h \
_cdio_stream.c \
_cdio_stream.h \
abs_path.c \
aix.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 \
memory.c \
mmc/mmc.c \
mmc/mmc_cmd_helper.h \
mmc/mmc_hl_cmds.c \
mmc/mmc_ll_cmds.c \
mmc/mmc_private.h \
mmc/mmc_util.c \
MSWindows/aspi32.c \
MSWindows/aspi32.h \
MSWindows/win32_ioctl.c \
MSWindows/win32.c \
MSWindows/win32.h \
netbsd.c \
osx.c \
read.c \
realpath.c \
sector.c \
solaris.c \
track.c \
utf8.c \
util.c
lib_LTLIBRARIES = libcdio.la
libcdio_la_LIBADD = $(LTLIBICONV)
libcdio_la_SOURCES = $(libcdio_sources)
libcdio_la_ldflags = -version-info $(libcdio_la_CURRENT):$(libcdio_la_REVISION):$(libcdio_la_AGE) @LT_NO_UNDEFINED@ $(DARWIN_PKG_LIB_HACK)
AM_CPPFLAGS = $(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: $(srcdir)/libcdio.sym
@echo 'CDIO_$(libcdio_la_MAJOR) { ' > $@
@echo ' global:' >> $@
@sed 's/^/ /;s/$$/;/' $< >> $@
@echo ' local:' >> $@
@echo ' *;' >> $@
@echo '};' >> $@
else
libcdio_la_LDFLAGS = $(libcdio_la_ldflags)
endif
MOSTLYCLEANFILES = libcdio.la.ver
|
