Re: [Boost-build] Help deciphering gcc.jam, please

From: Steve M. Robbins (steve_at_[hidden])
Date: 2008-04-05 23:29:52

On Tue, Apr 01, 2008 at 10:19:37PM +0400, Vladimir Prus wrote:
> On Sunday 09 March 2008 00:00:35 Steve M. Robbins wrote:

> > The standard layout for a shared library on linux (and several unix
> > variants) uses several files.  For a library like boost that
> > guarantees no compatibility between releases, there are two files:
> > 
> > 1) The shared library itself
> > 
> > 	libboost_program_options-mt-1.34.1.so.1.34.1
> > 	(soname: libboost_program_options-mt-1.34.1.so.1.34.1)
> > 
> > 2) A symbolic link to (1) for linking
> > 
> > 	libboost_program_options-mt-1.34.1.so
> 
> Why should we have the version number twice, both in name
> and soname? 

Actualy, we shouldn't; I was simply following current Boost
convention.  The more canonical unix convention is:

        libfoo.so.X.Y        (soname libfoo.so.X.Y)
        libfoo.so --> libfoo.so.X.Y

for version X.Y of library foo.  Then you can link with -lfoo without
having to specify the version of foo.  

If we can get both the toolchain and version removed from the link
libraries, then a major headache goes away;
c.f. http://svn.boost.org/trac/boost/ticket/1094

> I surely can add whatever new naming scheme you want. I guess the question
> I have now are:
> 
> 1. Why the version name is present twice?
> 2. Do you really need to encode variants in the name, like "mt"? 
> Why are you building all possible variants?

To answer the last question first: Debian packages all possible
variants because we don't know a priori which variant a user will
need.  If someone is building boost-using code and is handed a jam
file that requires libboost_program_options-mt-d-1.34.1.so.1.34.1, we
should have that available.

Your second question is a good one.  I'm not sure that we need to
encode variants in the name.  We're just following Boost, here.  I'm
not aware of any other library that does this to the extent Boost
does.  Most other libraries are either multithreaded or single
threaded, but rarely do they come in two flavours.  Also, most
libraries built with debugging symbols carry the same name rather than
being decorated with -d, but are put in a different directory.

The first question was addressed above.

Best regards,
-Steve