On Sep 26, 3:23 am, Martin Albrecht <[EMAIL PROTECTED]>
wrote:
> Hi Michael and [sage-devel],
>
> at
>
> http://trac.sagemath.org/sage_trac/ticket/4169#comment:7
>
> mabshoff makes the following comment:
>
> """
> The version patches by Tim break on every BSD and Solaris where we do not use
> the GNU ld per default. We now work around this by linking gld to ld, but
> this is *not* a long term solution. Sage in general does not benefit from
> versioned libraries, indeed they case a bunch of problems when linking
> extensions, due to the links the archives get larger and on top of that it
> makes the memory address space on Cygwin even more scare, so I intend to
> remove every one of those version patches in the future. Those patches should
> be moved into the Debian packaging directory or alternatively you should
> provide a makefile target for not versioned libraries.
> """
>
> As this seems to lay out a general strategy this seems too big to not discuss
> it here. Here are some -- clueless -- questions:
>
> - "Sage in general does not benefit from versioned libraries"
>
> Is adding a proper soname / library versioning to a library what you call
> versioned libraries? Isn't that somehow standardised and good practice?
Sure, on Linux and some Unix platforms. But doing it right, i.e. for
non-GNU linkers is complicated. I do not oppose using soname &
friends, but if we introduce them they ought to work on more than
Linux :)
> - "indeed they case a bunch of problems when linking extensions"
>
> Why?
For example: Take the FLINT.spkg - ever since we used the patches Tim
submitted the spkg was broken twice by either not adjusting the link
name for libfint.so or after installing an updated version Sage would
no longer start since we linked against libflint-1.0.13.so. We do need
to force a rebuild of the extensions that link against FLINT anyway,
so this is manageable, but just imagine what happens if we changed
ntl.
> - "due to the links the archives get larger"
>
> Do you mean the symbolic links? I don't see how they contribute to the size
> significantly.
Not the link, but not all tar utilities are smart enough to deal with
links properly. And saving a hundred or so MB install size seems to
matter.
> - "and on top of that it makes the memory address space on Cygwin even more
> scare"
>
> Can you elaborate on that?
Cygwin is stupid and often causes libraries to have collisions in
address space. So when you compile a bunch of DLL extensions for
Python (even Python's own) you need to rebase all the DLLs that can be
potentially loaded from an application. In Sage's case we are talking
about 190 extension in addition to numerous other DLLs. For example:
as is if I build Python 2.5 on my Cygwin install Python fails to start
since the socket extension has a address conflict with another DLL. So
one needs do drop out of all Cygwin shells and use the ash shell and a
script rebaseall (which in turn calls rebase.exe) to rebase all
libraries. To be 100% save you need to drop out of the build process
and rebase all DLLs everytime we build a native Python extension.
On top of the above the total address space on Cygwin is limited to
1.3GB. So having mutliple DLLs due to symlinks and sonames we
constrict *and* fragment the available address space even more.
> - "so I intend to remove every one of those version patches in the future"
*or* offer the option to build versioned or non-versioned libraries.
That should make either camp happy.
> To me this seems to be an issue that is better discussed first. Quite likely,
> you have very good arguments for the statements above (and you know way more
> about this than I'll ever know), but I would like to hear them first.
Well, all of the above IMHO clearly adds up to the conclusion I
arrived at :). I am not saying versioned libraries are bad in general,
but for the Sage project the disadvantages way outweigh the benefit.
So while versioned libraries are essential for the Debian project they
are a hassle for the Sage project.
> Cheers,
> Martin
Cheers,
Michael
> --
> name: Martin Albrecht
> _pgp:http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x8EF0DC99
> _www:http://www.informatik.uni-bremen.de/~malb
> _jab: [EMAIL PROTECTED]
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