Nick Hudson <skrll@netbsd.org> writes:
> > 
> > Log Message:
> > Add a target to generate a libtool archive file for libedit.
> 
> Please don't do this. At least not this way. Why do you need to fool
> libtool like this? Can I help?

If you've seen several commits related to "buildlink.mk" files lately,
it's because I'm experimenting with a way to very isolate the
libraries and headers available to the configure and build process of
packages.  This is an attempt to solve the "hidden dependencies"
problem.

This particular buildlink.mk deals with our libedit readline emulation
by optionally linking either the libedit library or the GNU readline
library and associated headers as ${BUILDLINK_LIBDIR}/libreadline.*
and as ${BUILDLINK_INCDIR}/readline/*.h.  This way, consumers of
readline can simply pass -I${BUILDLINK_INCDIR} and
-L${BUILDLINK_LIBDIR} to the compiler and can always find the readline
library by using "-lreadline".  This works very well except when
libtool is used to link a program.  In the case of amanda-client,
BUILDLINK_LIBDIR is /usr/pkgsrc/sysutils/amanda-client/work/lib, and
the following line:

/usr/pkg/bin/libtool --mode=link cc -O2 -mcpu=pentiumpro -mcpu=pentiumpro \
	-L/usr/pkgsrc/sysutils/amanda-client/work/lib			\
	-Wl,-R/usr/pkg/lib -L/usr/pkg/lib				\
	-L/usr/pkgsrc/sysutils/amanda-client/work/lib			\
	-Wl,-R/usr/pkg/lib -L/usr/pkg/lib  -L/usr/pkg/lib		\
	-o amrecover							\
	amrecover.o display_commands.o  extract_list.o help.o		\
	set_commands.o uparse.o uscan.o					\
	-lfl ../client-src/libamclient.la -lamanda -lreadline -ltermcap -lm

gets munged by libtool to:

cc -O2 -mcpu=pentiumpro -mcpu=pentiumpro				\
	-Wl,-R/usr/pkg/lib -Wl,-R/usr/pkg/lib				\
	-o .libs/amrecover						\
	amrecover.o display_commands.o extract_list.o help.o		\
	set_commands.o uparse.o uscan.o					\
	-L/usr/pkgsrc/sysutils/amanda-client/work/lib			\
	-L/usr/pkg/lib							\
	-lfl ../client-src/.libs/libamclient.so				\
	/usr/pkg/lib/libamanda.so					\
	/usr/pkg/lib/libreadline.so -ltermcap -lm			\
	-Wl,--rpath -Wl,/usr/pkg/lib

To my eyes, it's ignoring the libreadine.so library in
${BUILDLINK_LIBDIR} and using the libreadline.la in /usr/pkg/lib,
despite the fact that the former is listed earlier in the library
search path.  Unfortunately, I _really_ want to libreadline.so from
${BUILDLINK_LIBDIR} to be used, as it's a symbolic link to
/usr/lib/libedit.so.

If you examine the libtool line above, you can see that if those flags
were just passed to the compiler, my expectation that the compiler
would resolve "-lreadline" to the one in ${BUILDLINK_LIBDIR} because
that directory is specified earlier to the linker is met.
Unfortunately, libtool seems to first check for .la files in the
library search path first, then replace those libraries with the
corresponding .la files, then passing the results to the linker.
Given this algorithm, the only way I could think of to force libtool
to use the libreadline.* in ${BUILDLINK_LIBDIR} was to create a
libreadline.la in ${BUILDLINK_LIBDIR} so that it would be found
_before_ the one in /usr/pkg/lib.

What's the right way to do this?

	Thanks,

     -- Johnny C. Lam <lamj@stat.cmu.edu>
        Department of Statistics, Carnegie Mellon University
        http://www.stat.cmu.edu/~lamj/