Subject: Re: libtool, C++ shared libraries, and pthreads
To: None <>
From: Johnny C. Lam <>
List: tech-pkg
Date: 11/11/2004 16:02:54
Todd Vierling wrote:
> On Thu, 11 Nov 2004, Johnny C. Lam wrote:
>>On NetBSD 2.0, libtool doesn't correctly generate C++ shared libraries
>>if the shared library should also link against -lpthread.  Currently,
>>libtool uses:
>>	g++ -shared -nostdlib $predep_objects $libobjs $deplibs \
>>		$postdep_objects $compiler_flags \
>>		${wl}-soname $wl$soname -o $lib $postdeps
> Yeah, that's not entirely right, but the problem is, this is the globally
> generated shlib link command for g++ on GNU ld.  It's not a NetBSD-specific
> configuration.
> There's a way to fix this in the current libtool, however, until this is
> better addressed in libtool's upstream sources by not using -nostdlib:  on
> NetBSD, in, make -pthread trigger -lpthread automagically.  This
> is easy to do, so I'll go implement and test it now.  (It's not
> unprecedented; there's a special case for {Open,Free}BSD to omit -lc_r if
> supplied in favor of -pthread.)

I've attached the essential part of the changes to libtool that I wish 
to make to fix the libtool.m4 that differ from the current changes in 
manual-libtool.m4.  This correctly links -lpthread to the shared library 
when I build comms/gsmlib.

One side effect of this change is that the installed libtool archive no 
longer lists any of "-lstdc++ -lpthread -lgcc_s" in the dependency_libs 
line, although the shared library dependencies are still recorded in the 
shared library.  I think this is okay, but does anyone see any problems 
that may arise as a result?


	-- Johnny Lam <>