FreeTDS Development Group

[Jonathan Monroe <monroej_freetds AT actualtechnologies.com>]

On Feb 12, 2005, at 11:01 AM, Frediano Ziglio wrote:

> Il giorno lun, 07-02-2005 alle 11:49 -0600, Jonathan Monroe ha scritto:

> > On Feb 7, 2005, at 11:01 AM, Frediano ZIGLIO wrote:
> >
> > > > ODBC shared libraries gets the wrong name, *.so. Other shared
> > > > libraries
> > > > get the correct .dylib name.
> > >
> > > Before to say it's wrong it's best to try it... in 0.62 I changed 
> > > from
> > > .dylib to .so cause iODBC (bundled with Max OS X 10.2 if I remember)
> > > refuse to load dylib but loads .so (don't ask me why...)
> >
> > The iODBC libraries shipped with Darwin / OS X will load either a
> > .dylib or a .so (bundle).  The loader checks the library type and then
> > calls the correct loading routines.  I mentioned in a previous post
> > that Apple recommends that dylibs be built using "two level
> > namespaces":
> >
> > https://lists.ibiblio.org/sympa/arc/freetds/2004q1/015609.html
> >
> > Since the same symbols (SQLAllocHandle, etc) appear in both the driver
> > manager and the driver, the two level name space option ensures that
> > the application keeps the symbols separate.  There are situations 
> > where
> > conflicts occur when the libraries are built with flat name spaces.
> > I'm not sure if that's the problem you ran into - I can run the unit
> > tests with the library built as either a dylib or a bundle.
>
> Let's remember a bit of story. Mac OS X had some problem with library
> for some months we tried to fix it (trying changing libtool script with
> patch or even libtool version). The main problem is that there were 
> very
> few tester... If we change a line and we have to wait for a week or two
> this means that changing a line ten times require 2 months...
> After some time someone reported problems with ODBC (driver not 
> loaded).
> Someone else report a link to Apple pages that tell that iODBC
> implementation had problems... After some months we discovered that
> using bundle instead of .dylib fix the issue. So we add -module to
> Makefile.am and we had no more reports (happily). Some time ago we
> discovered also that instead of upgrading libtool we could change link
> script (and so we did... happily no reports).

I understand your frustration here.  I myself was never able to get the 
libraries to build on darwin until Mark Lilback posted his build 
instructions.  The standard *nix build tools have come a long way since 
then in terms of darwin support.  In 2005, it looks like most public 
projects include correct support for darwin in their build scripts.  It 
was a very different situation in 2003.

> Your mail, if I remember
> correctly, was in 0.62 RC phase so instead of trying to improve linking
> we "ignore" (not correct term...) your mail. Now we are still in RC and
> still this issue raise in a very bad period.

I apologize for not being more persistent about getting the changes 
implemented once 0.62 was released.  I'm just one user and I didn't see 
anyone else voice an opinion.  Since I wasn't able to make the changes 
myself, I just let it go.  In hind sight, I should have forced the 
issue.

> As you say current scripts
> work so for 0.63 they are fine.
>
> You spot however two problems:
> 1) two level namespaces
> 2) module format

If you're building a dylib, you should definitely build with two level 
namespaces for darwin 5.0 or later (versions earlier than 5.0 must use 
flat namespaces).  However, I think the real question is which type 
should be built - dylibs or bundles.

Dylibs seem to be the preferred library format for darwin in general.  
There are cases when a bundle might be a better choice.  I think a 
truly darwin friendly environment would support building both, much in 
the same way that both iODBC and unixODBC are supported.

> 1) Probably the solution is to check is Mac OS X (which version provide
> this option?)? and add -Wl,-twolevel_namespace to src/odbc/Makefile.am

darwin 5.0 or later:  two level namespace
else:  flat namespace

> 2) still problem is version. Which version support correctly
> loading .dylib??

I believe all versions of darwin support loading dylibs.  However, 
Apple only started including the iODBC driver manager libraries 
starting in darwin 6.

> All code I sent was from libtool output so another problem is: how
> libtool behave using -Wl,-twolevel_namespace and not using -module 
> under
> Mac OS X ??

I don't understand libtool at all, so I don't really understand your 
question.  However, if you give me some things to test, I will try them 
on various environments and report the results back to you.

Jonathan