Re: Build system cleanup

[Jan Stary <hans@stare.cz>]

On Aug 24 13:19:36, mans@mansr.com wrote:
> Jan Stary <hans@stare.cz> writes:
> 
> >> > cc [...] -o .libs/sox sox.o  -L./.libs -lsox -L/usr/local/lib -lpng [...]
> >> > cc [...] -o .libs/sox sox.o  -L/usr/local/lib -L./.libs -lsox -lpng [...]
> >> >
> >> > The first works, the second does not.
> >> > The only difference between the two is the place
> >> > where the extra -L/usr/local/lib gets added,
> >> > as described in the previous emails.
> >
> > And it seems libtool itself is the one who breaks it.
> > This is the failing line again:
> >
> > /bin/sh ../libtool  --tag=CC    --mode=link cc  -g -O2 -fstack-protector-strong -Wall -Wmissing-prototypes -Wstrict-prototypes   -avoid-version -module -L/usr/local/lib -Wl,--as-needed -o sox sox.o  libsox.la                      -lm
> >
> > Notice the "-L/usr/local/lib -Wl,--as-needed".
> > The "-L/usr/local/lib" part comes from the configure arg:
> >
> >   ./configure CC=cc CPPFLAGS=-I/usr/local/include LDFLAGS=-L/usr/local/lib
> >
> > The "-Wl,--as-needed" comes from
> >
> >   $ grep as-needed configure.ac
> >   AX_APPEND_LINK_FLAGS([-Wl,--as-needed])
> >
> > That results in the following line in src/Makefile:
> >
> >   LDFLAGS = -L/usr/local/lib -Wl,--as-needed
> >
> > and that's what is passed in the above command line. Now, libtool
> > apparently preprocesses the line into something else; in particular,
> > it reorders the options. The very next command is:
> >
> > libtool: link: cc -g -O2 -fstack-protector-strong -Wall -Wmissing-prototypes -Wstrict-prototypes -Wl,--as-needed -o .libs/sox sox.o  -L/usr/local/lib -L./.libs -lsox -lpng -lltdl -lao -lgsm -lmad -lmp3lame -ltwolame -lid3tag -lz -lopusfile -lopus -lsndio -lvorbisfile -lwavpack -lcrypto -lsndfile -lFLAC -lvorbisenc -lvorbis -logg -lm -Wl,-rpath,/usr/local/lib
> >
> > Notice where the -L/usr/local/lib has been moved.
> > As described previously, if it comes after -lsox
> > instead of before it, it links just fine.
> 
> None of this has changed.  The problem is that you have an old libsox in
> /usr/local/lib, and with that -L flag early in the command, it takes
> precedence over the just-built libsox, causing the link to fail.

This seems to be the case - together with GNU libtool
putting that -L/usr/local/lib _before_ the -L./.libs
which would link with the "new" libsox.

(And, indeed,
  $ nm /usr/local/lib/libsox.so.4.0 | grep lsx_malloc
  $ nm src/.libs/libsox.so.3.0 | grep lsx_malloc
  00042f60 T lsx_malloc
which was the actual unresolved symbol, among others).

I can confirm that deleting the previous version of sox
(installed in /usr/local/ via the OpenBSD sox-14.4.2p5 port)
makes that problem go away; or, better put, masks the bug
by removing the condition under which is shows.

> This whole issue is unique to OpenBSD.

Having a previous version installed while a new one
is being built is to be expected, right?

Searching for -lsox in the -L path is also perfectly normal.
As we now know, it is the order of the -L options
introduced by GNU libtool that breaks it.

Your "clean" VM is a special case in that it does not
have a previous version installed (as opposed to my screwed up,
misconfigured machine). When you install the previous sox 14.4.2
(pkg_add sox), does the

  ./configure CC=cc CFLAGS=-I/usr/local/include LDFLAGS=-L/usr/local/lib
  make V=1

build still work?

> On Linux and FreeBSD the link command uses the full filename of libsox,
> so it isn't searched for in the -L locations.

I didn't get to FreeBSD testing yet, but on NetBSD
(where the build fails in other interesting ways), it's

libtool: link: gcc -g -O2 -fstack-protector-strong -Wall -Wmissing-prototypes -Wstrict-prototypes -fopenmp -Wl,--as-needed -o .libs/sox sox.o  ./.libs/libsox.so -L/usr/pkg/lib -lmagic /usr/pkg/lib/libFLAC.so /usr/pkg/lib/libopusfile.so /usr/pkg/lib/libopus.so /usr/pkg/lib/libvorbisenc.so /usr/pkg/lib/libvorbisfile.so /usr/pkg/lib/libvorbis.so /usr/pkg/lib/libogg.so -lm -fopenmp -Wl,-rpath -Wl,/usr/local/lib -Wl,-rpath -Wl,/usr/pkg/lib

So even some of the external libraries are linked via absolute paths -
seems to be precisely those detected by pkg-config
(not sure what the point of pkg-config --libs is then);
the others (-lm -lmagic) are found in the -L path.

The linking commands are not invented by Linux or FreeBSD or OpenBSD
- they are what libtool or ./configure (or whatever it is inside the
auto* maze) put into the actual Makefile(s). If I understand the idea
of autotools at all, the supposed position of libtool is

	"Yo, I know how any given system/linker links;
	so I can issue the right linking commands
	for this system/linker right here, man".

What *is* unique about OpenBSD, then, is that GNU libtool
does in fact not know how to link here. Does that make sense?


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