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Re: Documenting the (dynamic) linking rules for symbol versioning

From: Florian Weimer <fweimer at redhat dot com>
To: "Michael Kerrisk (man-pages)" <mtk dot manpages at gmail dot com>, siddhesh at sourceware dot org, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
Cc: linux-man <linux-man at vger dot kernel dot org>, Carlos O'Donell <carlos at redhat dot com>, Rich Felker <dalias at aerifal dot cx>, "H.J. Lu" <hjl dot tools at gmail dot com>
Date: Fri, 5 May 2017 16:10:47 +0200
Subject: Re: Documenting the (dynamic) linking rules for symbol versioning
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On 04/20/2017 04:09 PM, Michael Kerrisk (man-pages) wrote:

On 04/20/2017 03:45 PM, Florian Weimer wrote:

On 04/20/2017 03:15 PM, Siddhesh Poyarekar wrote:

On Thursday 20 April 2017 06:31 PM, Florian Weimer wrote:

Hmm interesting, I thought 'latest' would imply the last version in the
sequence of versions in the map, but I guess it kinda makes sense that
it is the @@ default, similar to how a static linker would pick it up.


It might be another instance of bug 12977.  At least its fix will
involve preferring the default version in this case.  I don't know what


  From Michael's test case it seems like it already is preferring the
default version.  The fix would have to be to the comment that says
prefer the oldest version for regular unversioned lookups and the
*latest* for the dlsym lookups.

That or I misunderstood what you said.


I think it picked the default version by accident because of the way the
linker ordered the list.  But I could be mistaken.


How could I test your hypothesis? Just a longer chain of versions,
maybe? Or oddly named version tags?

I'm no longer sure what I actually saw during testing. May be theresults also depend on the binutils version. Based on source codeinspection in glibc, I think there actually is a problem here, but Ican't reproduce it with stock binaries.


Thanks,
Florian

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