dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Thu, Jun 04, 2009 at 12:37:57PM +0200, Johan Hake wrote:
> On Thursday 04 June 2009 12:23:59 Harish Narayanan wrote:
> > Martin Sandve Alnæs wrote:
> > > On Thu, Jun 4, 2009 at 11:14 AM, Johan Hake <hake@xxxxxxxxx> wrote:
> > >> On Thursday 04 June 2009 10:59:39 Johannes Ring wrote:
> > >>> On Thu, June 4, 2009 10:46, Johan Hake wrote:
> > >>>> [snip]
> > >>>>
> > >>>>> I don't have a problem with pkg-config being _the_ system,
> > >>>>> but the command line interface does not give that impression.
> > >>>>> It cannot be required that the user knows scons internals or takes
> > >>>>> even a casual glance at the implementation of the build system...
> > >>>>
> > >>>> True.
> > >>>>
> > >>>>> In particular, there is no mention of pkg-config in scons --help,
> > >>>>> README, or INSTALL, and the help messages do not suggest
> > >>>>> that they may be ignored if the wind comes from the north:
> > >>>>> withPetscDir: Specify path to PETSc ( /path/to/withPetscDir )
> > >>>>
> > >>>> Also true.
> > >>>>
> > >>>>> If scons makes it hard to design the interface freely, why not
> > >>>>> have a separate script to generate selected pkg-config files?
> > >>>>> I don't care more for "scons configFoo" than
> > >>>>> "configure withFooDir=/here/I/am withBarDir=/here/I/am".
> > >>>>>
> > >>>>> Whatever solution is chosen, it must be possible to say
> > >>>>> explicitly that "hey, I want to use foolib from /bar/foolibdir,
> > >>>>> please make me a pkg-config file for that build and ignore
> > >>>>> any global defaults that you find".
> > >>>>
> > >>>> Ok, I can discuss it with Johannes and see if there are any good
> > >>>> solution for
> > >>>> this.
> > >>>>
> > >>>> Suggestion 1:
> > >>>> Trigger construction of a specific pkg-config file during compilation.
> > >>>>
> > >>>>   scons configFoo configBar
> > >>>>
> > >>>> These options will come in addition to other options. Maybe more
> > >>>> explicit towards mentioning pkg-config
> > >>>>
> > >>>>   scons generatePkgConfigFoo generatePkgConfigBar?
> > >>>>
> > >>>> Suggestion 2:
> > >>>> Put the generation of pkg-config files into a standalone script.
> > >>>>
> > >>>>   generate-pkg-config Foo Bar
> > >>>>
> > >>>> Instead of generate-pkg-config-file we could for example have:
> > >>>>
> > >>>>   dolfin-config, config?
> > >>>>
> > >>>> I think 1 integrates better with the present system.
> > >>>>
> > >>>> Any comments from the others?
> > >>>
> > >>> I like better suggestion 1, however, it should be possible to generate
> > >>> new pkg-config files whenever withFooDir=/path/to/foo is specified on
> > >>> the command line. Isn't that better?
> > >>
> > >> Maybee, less options is good. However as it is now this will then be
> > >> cached, and scons will trigger the build each time.
> > >>
> > >> A solution that might work is to make that option uncachable. So
> > >> whenever withFooDir=/path/to/foo is explicitly used we try to generate a
> > >> pkg-config file. Anyhow that option is only used once, for building
> > >> Foo's pkg-config file (if not any others are found on the system :) ) so
> > >> making it an uncached option would make sense.
> > >>
> > >> However it is not very logical that the construction of a pkg-config
> > >> file should be triggered when a directory is passed.
> > >>
> > >> Johan
> > >
> > > A related issue: it is very common to run "scons <options>", look at the
> > > output, and abort the build with ctrl+c if some library isn't found. It
> > > would be nice if we had a configuration step that didn't start the build.
> > > This step should probably be the same as what's discussed above?
> >
> > And the opposite would be nice too. i.e. To be able to do scons
> > <something> and not need to configure.
> >
> > e.g. I was having some trouble with boost and so I removed it. I then
> > tried to unmake and uninstall dolfin by scons -c and scons -c install,
> > and they both fail because of a lack of boost (which gets flagged on an
> > unnecessary configure).
> 
> Splitting the build and configure part is kind of logical. I think the simula 
> scons was built to remove the distintion between these two ;) However the 
> complexity of dolfin starts to require more composite logics.
> 
> So, based on the options passed to the configuration step, enableFoo 
> withFooDir aso, we check whats available, create pkg-config files store them 
> locally. Give the user information about the result of the config step.
> 
> The build step will then just build (or clean) what ever specified in some 
> cached option file, which is generated by the configure step.
> 
> Any locally stored pkg-config files produced from the configure step will be 
> installed during an installation step.
> 
> This should be possible with some refactoring of the code, but I think we need 
> some consensus about it. simula scons is also used by other packages too.

I agree. We need configure + build:

1. The configure step checks for required packages, using pkg-config.

2. If a required package is not found, it tries to generate the
pkg-config file.

3. The build step just builds, using pkg-config to get libraries.

This way, caching is the same as stored configuration so there should
be little confusion about caching.

-- 
Anders

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