[petsc-dev] Fwd: [petsc-users] cannot find 'libz.a' when configuring

[Satish Balay]

On Thu, 11 Apr 2013, Satish Balay wrote:

> > > > > > We have had this same discussion a million times, and we always
> > > > > eventually
> > > > > > get to the same answer and forget. Do we need our own error message
> > > for
> > > > > > petsc-dev?
> > > > > >
> > > > > > We cannot possibly guess everything that can go wrong. What we need
> > > is a
> > > > > > system
> > > > > > where the user can specify what he actually wants and we check it.
> > > So,
> > > > > zlib
> > > > > > and
> > > > > > everything else are optional dependencies for hdf5. If something is
> > > not
> > > > > > specified, it
> > > > > > fails, and the user goes back and specifies the right thing.
> > > > >
> > > > > Sure - but specify how? specify everything with
> > > > > --with-hdf5-lib,--with-hdf5-include options?
> > > > >
> > > > > Or somehow he knows that he has to specify
> > > > > --with-zlib-include/-with-zlib-lib options?
> > > > >
> > > >
> > > > This. It would be nice if HDF5 would tell us about its dependencies, but
> > > if
> > > > it does not, then
> > > > the user has to, and this is our system (packages).
> > >
> > > So we would start adding zlib.py, szip.py and manymore [and support
> > > --download-zlib --download-szip]. And if user gets the error:
> > >
> > > --with-hdf5-dir=/foo/bar does not work.
> > >
> > > So he/she send us configure.log
> > >
> > > Then we look at it and respond saying: you need to specify --with-zlib-dir
> > > --with-szip-dir options aswell.
> > >
> > > Does this look right?
> > 
> > 
> > Yes, that is what I think makes sense.
> > 
> > We can always try to add another layer that 'greps' for libz in the hdf5
> > error message and guesses that
> > the user forgot it, but hopefully before we get to it, a sane storage
> > library appears, or HDF5 gets its act
> > together.
> 
> In this case - why bother with libz.py and szip.py? Why not tell the
> user to specify hdf5 completely with --with-hdf5-include and
> --with-hdf5-lib options?
> 
> Just printing the link errors on the screen might be sufficient to
> clue in the user. Currently its hidden inside configure. [And its not
> clear which of the 10 tests configure did for this case should be
> printed on the screen as the appropriate message]

I might have been the one that advocated self.needsCompression approach thats
currently in configure.

This is currently used only by hdf5.py.

My current thought is to strip it out - and just add it to hdf5.py as:

    self.liblist   = [['libhdf5.a','libhdf5_hl.a'],'['libhdf5.a','libhdf5_hl.a','libz.a'],['libhdf5.a','libhdf5_hl.a','zlib.lib']]

This would be equivalent to the current functionality - and perhaps
what was there previously - before we wanted better error messages and
detection of zlib. Since this is not possible anyway why bother
with the additional complexity?

Satish