Serious problem with standard library paths and order of -L flags

[Jelmer Vernooij]

On Tue, Jun 17, 2014 at 03:11:09PM +0200, Michael Adam wrote:
> On 2014-06-17 at 14:13 +0200, Jelmer Vernooij wrote:
> > On Tue, Jun 17, 2014 at 01:52:20PM +0200, Michael Adam wrote:
> > > ...
> > > 
> > > I have two patches hacked into our waf build (pair-hacked
> > > with Metze) that makes the internals skip a library path
> > > handed in from (e.g.) pkg-config if it is a standard or
> > > well-known library path. This fixes it for me on my
> > > ubuntu 64 bit system, but of course this is not portable!
> > > (patches attached...)
> > > 
> > > ==> Question to the list (Jelmer?...):
> > > 
> > > Is there a good way to retrieve a list of "standard"
> > > library paths from the system (via python)?
> > > 
> > > (Or does anybody have an idea how to solve this differntly?)
> > 
> > I agree with the thoughts behind the change.
> > 
> > Please don't modify the upstream waf source
> > (buildtools/wafadmin), but rather do this by wrapping things in
> > wafsamba. Otherwise we won't be able to update to newer
> > versions of waf.
> 
> I'll do that if possible.
> Last time, there was a -L flag ordering problem,
> I fixed it in wafadmin and ita brought my patch
> upstream. If there is no bug generic in waf,
> I'll fix it in wafsamba.
> 
> > We should probably also support more platforms than just x86_64-linux.
> 
> Sure. That was just an example... Hence my mail. :)
> 
> > Note that pkg-config will by default filter out standard system
> > paths (see its manpage). It will only output -L/usr/lib if you
> > set PKG_CONFIG_ALLOW_SYSTEM_LIBS.
> 
> Ah! Good to know.
> 
> > Ideally we should be relying on pkg-config instead of custom
> > tools like cups-config that are broken.
> 
> Hm, but I don't think we can avoid cups-config for cups.
> I just checked: on my system cups-config is a shell script
> that does this somewhere:
> 
>     if test $libdir != /usr/lib -a $libdir != /usr/lib32 -a
>     $libdir != /usr/lib64; then
>          LDFLAGS="$LDFLAGS -L$libdir"
>     fi
> 
> So it has some code to exclude system paths, but that is
> not portable... :-/
> 
> Thanks for your input, still uncertain what to
> do for cups though.
> 
> And, by the way, python-config has a similar problem
> (which was what hit us in the referenced bug #10515).
> "python-config --ldflags" contains "-L/usr/lib" on my
> system. And there does not seem to be a way to disable
> this.
> 
> It seems there is a pkg-config file for python, so one
> could possibly use pkg-config. But wafadmin uses python-config.

I guess this would affect other waf users too. CC'ing Thomas to see if he has
any thoughts on this. Would this be something waf could do?

Cheers,

Jelmer