libtool makes it hard to create multithreaded programs on HP-UX

[Bruno Haible]

Hi,

A special "feature" in libtool 1.5.24 is making some multithreaded programs
nonfunctional on HP-UX 11.00.

To reproduce:

Get and unpack http://www.haible.de/bruno/gnu/gettext-0.16.2-pre6.tar.gz .

$ export PATH=/usr/bin:$PATH
$ export CC="cc -Ae" CXX="aCC"
$ cd gettext-0.16.2-pre6
$ ./configure
$ make
$ cd gettext-tools/gnulib-tests
$ make test-lock
        source='test-lock.c' object='test-lock.o' libtool=no \
        DEPDIR=.deps depmode=hp /bin/sh ../../build-aux/depcomp \
        cc -Ae -DHAVE_CONFIG_H -I. -I..  -I. -I.  -I.. -I./..  -I../gnulib-lib 
-I./../gnulib-lib    -g -c test-lock.c
        /bin/sh ../libtool --tag=CC    --mode=link cc -Ae  -g    -o test-lock 
test-lock.o ../gnulib-lib/libgettextlib.la -lpthread -lrt 
mkdir .libs
chmod 777 .libs
libtool: link: warning: this platform does not like uninstalled shared libraries
libtool: link: `test-lock' will be relinked during installation
cc -Ae -g -o .libs/test-lock test-lock.o  ../gnulib-lib/.libs/libgettextlib.sl 
/udd/marceau/gettext-0.16.2-pre6/gettext-tools/intl/.libs/libintl.sl -lc 
-lcurses -lpthread -lrt  -Wl,+b 
-Wl,/udd/marceau/gettext-0.16.2-pre6/gettext-tools/gnulib-lib/.libs:/udd/marceau/gettext-0.16.2-pre6/gettext-tools/intl/.libs:/usr/local/lib
creating test-lock
$ ./test-lock
Starting test_lock ...ABORT instruction

The problem is that pthread_create() returns ENOSYS instead of creating a
thread and returning 0.

[1] explains that pthread_create is only a stub in libc, and well defined
in libpthread. If a program is linked with "-lc -lpthread", the stub in
libc will take precedence. If a program is linked with just "-lpthread",
or with "-lpthread -lc", the well defined function in libpthread takes
precedence.

test-lock was created like this:

    /bin/sh ../libtool --tag=CC    --mode=link cc -Ae  -g    -o test-lock \
      test-lock.o ../gnulib-lib/libgettextlib.la -lpthread -lrt

So I try to put the -lpthread once before and once after libgettextlib.la:

$ /bin/sh ../libtool --tag=CC    --mode=link cc -Ae  -g    -o test-lock \
    test-lock.o -lpthread ../gnulib-lib/libgettextlib.la -lpthread -lrt
libtool: link: warning: this platform does not like uninstalled shared libraries
libtool: link: `test-lock' will be relinked during installation
cc -Ae -g -o .libs/test-lock test-lock.o  ../gnulib-lib/.libs/libgettextlib.sl 
/udd/marceau/gettext-0.16.2-pre6/gettext-tools/intl/.libs/libintl.sl -lc 
-lcurses -lpthread -lrt  -Wl,+b 
-Wl,/udd/marceau/gettext-0.16.2-pre6/gettext-tools/gnulib-lib/.libs:/udd/marceau/gettext-0.16.2-pre6/gettext-tools/intl/.libs:/usr/local/lib
creating test-lock
$ ./test-lock
Starting test_lock ...ABORT instruction

As you can see, this had no effect on the cc command line: libtool has moved
the -lpthread so that it comes after -lc.

So I try to create the test-lock program differently, bypassing libtool:

$ cc -Ae -g -o .libs/test-lock test-lock.o  
../gnulib-lib/.libs/libgettextlib.sl 
/udd/marceau/gettext-0.16.2-pre6/gettext-tools/intl/.libs/libintl.sl -lpthread 
-lc -lcurses -lrt  -Wl,+b 
-Wl,/udd/marceau/gettext-0.16.2-pre6/gettext-tools/gnulib-lib/.libs:/udd/marceau/gettext-0.16.2-pre6/gettext-tools/intl/.libs:/usr/local/lib
$ ./test-lock 
Starting test_lock ... OK
Starting test_rwlock ... OK
Starting test_recursive_lock ... OK
Starting test_once ... OK

Conclusion: libtool's positioning of -lc before -lpthread causes the problem.

The -lc actually comes from the libintl library: It is created through
  /bin/sh ../libtool --mode=link cc -Ae  -g    -o libintl.la gettext.lo ... \
    -lc -version-info 8:1:0 -rpath /usr/local/lib -no-undefined
and without the "-lc" the -no-undefined option causes an error on many
platforms.

The value of build_libtool_need_lc is irrelevant for this issue.

I can solve the problem by omitting the -lc from the libtool command line
for libintl (specially for HP-UX). But why is libtool reordering my link
specifications at all?

Bruno

[1] http://docs.hp.com/en/1896/pthreads.html