Re: -no-undefined support for GNU/Linux

[Ralf Wildenhues]

* Mike Frysinger wrote on Wed, Mar 18, 2009 at 09:27:42AM CET:
> On Wednesday 18 March 2009 03:00:07 Ralf Wildenhues wrote:
> >
> > IIRC lots of things would break on Linux if we used -Wl,--no-undefined.
> > I don't recall the details, but I'm sure glibc wasn't the only problem
> > child in this area.
> 
> rather than make it the default, i would expect the flag to only show
> up when people have explicitly done -no-undefined.

Yes, that's what I meant.  Sorry for not being explicit.

>  the breakage there shouldnt be too bad right ?

Well, lots of packages that have been ported to w32 use -no-undefined on
all systems, as Eric already noted.  Generally works ok, though IIRC it
was pretty guaranteed to break on GNU/Linux due to support library
issues.  I don't recall whether that was glibc only, or GCC stuff as
well.  But anyway we need to collect data on such a change.

> > Before we do this, I'd like to see some real-world exposure of it, say,
> > using it to build the better part of a distribution or so.  Running the
> > Libtool testsuite with it would be a good starter.  :-)
> 
> i dont have a problem running it on my Gentoo systems ... pretty easy to 
> rebuild quite a bit of packages there

Well that would be very nice if you could try that.

> but a patch would be needed first ... there's the previous one in the 
> archives 
> that was ported to libtool-1.5 ...

Do you have a URL handy?  Anyway, should be little more than this patch,
I guess.

Thanks,
Ralf

    Enable -Wl,--no-undefined on GNU/Linux.
    
    * libltdl/m4/libtool.m4 (_LT_LINKER_SHLIBS) [linux]
    <no_undefined_flag>: Set to `${wl}--no-undefined'.
    Suggestion by Mike Frysinger.

diff --git a/libltdl/m4/libtool.m4 b/libltdl/m4/libtool.m4
index b6f9f06..c8ab17d 100644
--- a/libltdl/m4/libtool.m4
+++ b/libltdl/m4/libtool.m4
@@ -4311,6 +4311,7 @@ _LT_EOF
       if $LD --help 2>&1 | $EGREP ': supported targets:.* elf' > /dev/null \
         && test "$tmp_diet" = no
       then
+       _LT_TAGVAR(no_undefined_flag, $1)=' ${wl}--no-undefined'
        tmp_addflag=
        tmp_sharedflag='-shared'
        case $cc_basename,$host_cpu in