[lldb-dev] dlsym() and RTLD_FIRST

Zachary Turner zturner at google.com
Thu Aug 21 16:22:24 PDT 2014

This seems like the only case we ever want, so I'm going to post a patch to
LLVM's DynamicLibrary class to use RTLD_FIRST on Apple, and a similar
method of checking the module filespec on other platforms, and see if they
accept it.  If so, I will convert our Plugin code to use LLVM's
DynamicLibrary and then delete our DynamicLibrary

On Thu, Aug 21, 2014 at 4:08 PM, Greg Clayton <gclayton at apple.com> wrote:

> > On Aug 21, 2014, at 3:31 PM, Zachary Turner <zturner at google.com> wrote:
> >
> > Can someone explain this flag to me?
> It says "only look in this binary, don't look in any others. We are
> looking for a plug-in initialization function and we don't want to get one
> back from another dylib.
> As Enrico said, the email from a while back details this:
> http://comments.gmane.org/gmane.comp.debugging.lldb.devel/305
> >  I've read the documentation, but it's still not clear to me.  If you
> ask dlsym() to search some module X, why would it ever search modules other
> than X?
> I don't know but it does.
> >
> > The reason I ask about this is that llvm support library already has a
> DynamicLibrary class whose purpose almost exactly matches what we're using
> the Host::DynamicLibrary related functions for.  However, it doesn't use
> the RTLD_FIRST flag, and so I'm not sure what the implications are of us
> using it and deleting our own DynamicLibrary code.
> It would be nice if we could specify this flag so we either find the
> symbol from libx.dylib or we don't. We don't want to find the symbol in
> liby.dylib and call it in our case.
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