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Re: Building a static library consisting of libraries

From: Ralf Wildenhues
Subject: Re: Building a static library consisting of libraries
Date: Tue, 13 Jun 2006 09:03:05 +0200
User-agent: Mutt/1.5.11

* Norbert Sendetzky wrote on Mon, Jun 12, 2006 at 08:59:07PM CEST:
> On Monday 12 June 2006 12:57, Ralf Wildenhues wrote:
> > Mixing Libtool and non-Libtool libraries isn't the best idea.  Better to
> > mix libtool libraries
> >   lib_LTLIBRARIES =
> >
> > and libtool static libraries
> >   lib_LTLIBRARIES =
> >   libbar_la_LDFLAGS = -static
> >
> > and libtool convenience archives
> >   noinst_LTLIBRARIES =
> Let me first ask a question: Are .a libraries (libopendbx.a) static
> libraries

Usually, yes.  (Exceptions: on w32, static libraries may end in .lib, on
AIX libraries in .a may be shared.)

But I think you are asking about the Automake/Libtool abstraction:
there, the model is:
  libfoo.a   is always a static library  is a Libtool abstraction that can be any of the three
             mentioned above.

If you use Libtool, it's better to not use the .a libraries at all --
libtool static libraries provide this then.

> or is that only dependent on the -static flag?

When you create a library, the link flag -static to libtool means that
it should create only a static library.

> I ask because
> my understanding may be wrong, which depends on automake creating .a
> files if --enable-static is used.

Yes.  Without -static, libtool may create a shared library, a static, or
both, depending on the system's features, configure flags, link flags.

> > If with this information you still get errors, then please show
> > what's going wrong in more detail (link command lines plus output,
> > and/or snippets; cut and paste is much more helpful
> > than describing errors; of course a reproducible example is best).
> My in lib:
> include_HEADERS = odbx.h
> libopendbx_la_SOURCES =  odbxlib.c odbxlib.h odbx.c odbxdrv.h
> libopendbx_la_CFLAGS = @PKGCFLAGS@
> libopendbx_la_CPPFLAGS = -DLIBPATH=\"$(pkglibdir)/\"
> libopendbx_la_LDFLAGS = -version-info @LIBVERSION@
> lib_LIBRARIES = libopendbx.a
> libopendbx_a_SOURCES = odbxlib.c odbxlib.h odbx.c odbxdrv.h
> libopendbx_a_CFLAGS = @PKGCFLAGS@
> libopendbx_a_CPPFLAGS = -DODBX_STATIC
> libopendbx_a_LDFLAGS = -static
> libopendbx_a_LIBADD = $(top_builddir)/backends/mysql/
> A of a backend:
> pkglib_LTLIBRARIES =
> libmysqlbackend_la_SOURCES = mysqlbackend.c mysqlbackend.h
> libmysqlbackend_la_CFLAGS = @PKGCFLAGS@
> libmysqlbackend_la_LDFLAGS = -module -version-info @LIBVERSION@
> libmysqlbackend_la_LIBADD = address@hidden@
> noinst_LTLIBRARIES =
> libmysqlstatic_la_SOURCES = mysqlbackend.c mysqlbackend.h
> libmysqlstatic_la_CFLAGS = @PKGCFLAGS@
> libmysqlstatic_la_CPPFLAGS = -DODBX_STATIC
> libmysqlstatic_la_LDFLAGS = -static
> libmysqlstatic_la_LIBADD = address@hidden@
> This generates an invalid libopendbx.a which contains the libopendbx object 
> and an invalid file:

You should never add libtool libraries to non-libtool libraries.
If you want libmysqlstatic to end up completely subsumed into
libopendbx, then make the former a libtool convenience archive, and the
latter a libtool library (static or not).

But you should note that @LIBMYSQL@ will not end up subsumed in
libopendbx, if @LIBMYSQL@ is not a convenience archive (which implies
that it is uninstalled).  This would easily get you duplicate symbols,
if your resulting libopendbx would then be linked together with other
libraries depending on @address@hidden  However, the libtool library will
contain the dependency information on @LIBMYSQL@, so this:

> make[2]: Entering directory `/home/nose/Project/opendbx/devel/test'
> /bin/sh ../libtool --tag=CC --mode=link gcc -std=gnu99  -g -O2   -o 
> odbxtest-static  odbx-regression.o ../lib/libopendbx.a
> gcc -std=gnu99 -g -O2 -o odbxtest-static 
> odbx-regression.o  ../lib/libopendbx.a
> ../lib/libopendbx.a(libopendbx_a-odbxlib.o):(.data+0x4): undefined reference 
> to `mysql_odbx_ops'

should then work.

OK now?


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