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Re: soname (was Re: [ft-devel] Freetype library for LSB)

From: Behdad Esfahbod
Subject: Re: soname (was Re: [ft-devel] Freetype library for LSB)
Date: Mon, 25 Jul 2005 21:36:21 -0400 (EDT)

On Mon, 25 Jul 2005, Owen Taylor wrote:

> -export-symbols is pretty straightforward to use - we use it (or
> actually, -export-symbols-regex for Pango). You probably could build
> the symbol file pretty easily by scanning the for FT_EXPORT ...
> well, if you didn't use that for internal symbols.

Ulrich Drepper writes in his paper [1]:

2.2.6 Libtool's -export-symbols


Interesting for us here is the code the linker produces using
this method.  For the GNU linker Libtool converts -export-symbols
option into the completely useless -retain-symbols-file option.
This option instructs the linker to prune the normal symbol
tables, not the dynamic symbol table.  The normal symbol table
will contain only the symbols named in the export list file plus
the special STT_SECTION symbols which might be needed in
relocations.  All local symbols are gone.  The problem is that
the dynamic symbol table is not touched at all and this is the
table which is actually used at runtime.

The effect of the using libtool this way is that programs reading
the normal symbol table (for instance nm) do not find any symbols
but those listed in the export list. Neither have any symbols
been made unavailable for the dynamic linker, nor have any normal
relocations been converted into relative relocations.

The only reason this method is mentioned here is that there is
hope libtool will learn about converting the export lists into
the anonymous version maps we have seen in the previous section
when the GNU linker is used.  At that point libtool will become
useful.  Until then relying on its -export-symbols option is
misleading at best.

Don't know if this has changed since.  A quick look at the
libtool ChangeLog doesn't suggest any.  CC'ing

[1] http://www.livejournal.com/users/udrepper/2491.html


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