Re: png2/3 problem apparently successfully solved with -Bsymbolic
On Tue, 20 Aug 2002, Luca Barbieri wrote:
> I propose to do the following to solve the libpng2/3 problem. I've
> recompiled libpng2. libpng3 and libgtk2.0-0png3 locally and the system
> seems to work correctly.
> 1. Recompile libpng2 and libpng3 with -Bsymbolic
Well, either this or using versioned symbols is required, and would have
almost the same effect.
> 2. Recompile all libraries that use either libpng2 or libpng3 to
> explicitly link to them and to use -Bsymbolic
This should not be needed if versioned symbols are used. Do note that if you
compile something with -Bsymbolic, you cannot override the symbols it
both defines and uses. So, -Bsymbolic is more prone to cause side-efects
than versioned symbols.
> Note2: "recompile with -Bsymbolic" means "add -Wl,-Bsymbolic to the
> flags passed to the compiler in the linking stage, rebuild and upload
> the new package"
Versioning would be -Wl,-soname,$@.$(MAJOR) where $(MAJOR) is the
versioning we want to apply.
> I'll now explain what the problem is and why this solution works.
> The problem is that libpng2 and libpng3 have symbols with different
> names and we want to have both loaded in the same address space.
I would like to have them in different address spaces, thank you very much
:) That's what symbol versioning does.
> So we can solve this by making sure that anything that wants to use png
> 1. Directly links to the desired version of libpng
> 2. Is either the main program or is linked with -Bsymbolic
(2) should NOT be needed. At least not if the explanation of -Bsymbolic drow
gave me on IRC (which seems to be what the ld info page says about the
matter) is correct.
Could you try that again without using -Bsymbolic in anything but png2 and
> Are there any problems that would be caused by these changes?
Well, -Bsymbolic is rumored not to be very portable, but as long as ld
supports it in all of our archs, that's a moot problem.
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