Re: Unhelpful error message in libltdl

[Ralf Wildenhues]

* John Bytheway wrote on Sat, Mar 08, 2008 at 08:18:12PM CET:
> Ralf Wildenhues wrote:
> > I've given your bug description a
> > shot at a test that exposes this issue, but have so far failed.  Below
> > is where I'm at, patch against current HEAD.  Can you point me to how
> > your setup is different?  Specifically, how do you get a failure of
> > dlopen due to an undefined symbol on GNU/Linux when RTLD_NOW is not set?
> 
> Ah, yes.  I hadn't realised quite how tricky it is; one answer (the one
> that I encountered) is to have an undefined reference to a vtable in
> C++.  I've included a patch below on your proposed lt_dlopen.at which
> uses this method.  I'll leave it to someone else to try to construct an
> equivalent example in C.  I had to make my best guess at the correct
> syntax for compiling C++ in this context (I've never encountered
> autotest before).  Note also that I removed dep.c and associated stuff
> which seemed to be an unnecessary extra level of confusion.
> 
> However, this is not the end of the story.  If you run this test you
> should see the "file not found" error which was exactly the unhelpful
> error which my original patch was supposed to fix, so clearly something
> still isn't right.

Hmm.  I have some qualms with this additional patch to ltdl.c.  To make
my life easier, rather than thinking about whether that can pessimize
legitimate uses (which I'm pretty sure it does) and how that can be
avoided, I'd like to go back a step first.  Your first patch against
ltdl.c clearly fixed some issue for you, no?  Let's try to only deal
with that issue for now and construct a testcase for that.  It can be
C++ or another language, it can be system-specific no matter what, all
I'd like is a reproducible example in some way that matches what that
patch fixes.

If you have problems with autotest, it's really fine if you just post
some C++ code (or describe it if you must) that exposes it.  Thank you.

Cheers,
Ralf