libltdl problems with C++ library

[Olivier Boudeville]

Hi everybody,

I am trying to use libtool and libltdl to develop a C++ library (named
Ceylan) that provides some services, including plugin support. Despite
the reading of libltdl documentation and of the autobook, I am facing
link problems with the unit test (testCeylanPlugin) for plugin support
(test plugin is ceylan-test-plugin.la, it would need some other services
provided by libCeylan.la), as if the STL symbols could not be found
despite the various flags :

"""
creating .libs/testCeylanPluginS.c
generating symbol list for `testCeylanPlugin'
extracting global C symbols from
`testCeylanPlugin.o'                                                            
    

[..]
g++ -g -ggdb -O0 -fno-inline -Wall -Werror -Woverloaded-virtual -W
-Wfloat-equal -Wundef -Wendif-labels -Wshadow -Wpointer-arith
-Wcast-qual -Wcast-align -Wwrite-strings -Wconversion -Wsign-compare
-Wmissing-format-attribute -Wpacked -Wredundant-decls
-Wno-unused-parameter -ansi -pedantic-errors -o .libs/testCeylanPlugin
.libs/testCeylanPluginS.o testCeylanPlugin.o -Wl,--export-dynamic 
-L/home/sye/tmp-Ceylan-test-install/lib -L/usr/i686-pc-linux-gnu/bin
-L/usr/i686-pc-linux-gnu/lib
-L/usr/lib/gcc-lib/i686-pc-linux-gnu/../../../i686-pc-linux-gnu/lib
./.libs/ceylan-test-plugin.so
/home/sye/tmp-Ceylan-test-install/lib/libCeylan.so
/usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6/libstdc++.so -lm -lgcc_s -lc
/home/sye/tmp-Ceylan-test-install/lib/libltdl.so -ldl -lpthread
-Wl,--rpath -Wl,/home/sye/tmp-Ceylan-test-install/lib
.libs/testCeylanPluginS.o:(.rodata+0x3044): undefined reference to
`std::_Base_bitset<(unsigned)1>::_M_do_find_next(unsigned, unsigned) const'
.libs/testCeylanPluginS.o:(.rodata+0x304c): undefined reference to
`std::_Base_bitset<(unsigned)1>::_M_do_find_first(unsigned) const'  
.libs/testCeylanPluginS.o:(.rodata+0x30c4): undefined reference to
`std::__enc_traits::_S_max_size'
.libs/testCeylanPluginS.o:(.rodata+0x3314): undefined reference to
`__gnu_cxx::facet_name'
.libs/testCeylanPluginS.o:(.rodata+0x331c): undefined reference to
`__gnu_cxx::messages_c'
.
[...]
""""

(one thing I do not understand is why
"/usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6/libstdc++.so" is specified
this way, I would have expected
"-L/usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6 -lstdc++"; I tried to run
that command manually but the link error remained)

In configure.in I have indeed
"""
AC_LIBTOOL_DLOPEN
AM_PROG_LIBTOOL
"""                                

but libtool says :

"""
*** Warning: Linking the executable testCeylanPlugin against the
loadable module
*** ceylan-test-plugin.so is not portable!
libtool: link: warning: `AC_LIBTOOL_DLOPEN' not used. Assuming no dlopen
support.      
"""

In my Makefile.am I have :

"""
testCeylanPlugin_SOURCES   = testCeylanPlugin.cc
testCeylanPlugin_LDFLAGS = -export-dynamic -no-undefined -dlpreopen
force -dlopen self -dlopen ceylan-test-plugin.la
testCeylanPlugin_LDADD   = $(LIBLTDL)
testCeylanPlugin_DEPENDENCIES = $(LIBLTDL) ceylan-test-plugin.la


lib_LTLIBRARIES = ceylan-test-plugin.la

ceylan_test_plugin_la_SOURCES = ceylan-test-plugin.cc
ceylan_test_plugin_la_LDFLAGS = -no-undefined -module -avoid-version
"""                       

I tried various combinations (specifying convenience/installable
libltdl, declaring the plugin with extern "C", using a pure-C plugin,
playing with the numerous link options in Makefile.am) with no luck for
the moment.

Does anybody have a clue, or know the proper way to set up this ?

Thanks in advance,
regards,

Olivier.

PS: the desired layout would be : libCeylan (which is C++) can load any
plug-in, including C++ ones, including plug-in needing some services
provided by libCeylan and the STL