only perfom when the output is missing

[Faré]

That would be a great extension to have for ASDF in general, but would
have to be an extension, unless the maintainer is willing to put the
implementation of a fast hash function in ASDF. If so, I nominate
BLAKE3. It should take a few hundreds of lines of code—a relatively
small amount by ASDF 3.3 standards. And if the entry function is
not-inline, like all UIOP functions, it can be replaced by a very fast
implementation when a suitable cryptographic library is loaded.

—♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org
He who says he will die for a cause will probably lie for it and may kill
for it.  — John McCarthy


On Sat, Apr 17, 2021 at 7:29 PM Robert Goldman <rpgoldman at sift.info> wrote:
>
> On 17 Apr 2021, at 17:09, Faré wrote:
>
> > One way to avoid unneeded regeneration in the future without lying
> > about the dependency would be to modify the script to:
> > 1. Remember in the output the hash of the input.
> > 2. In the regeneration script, have a shortcut that leaves the output
> > unchanged if the input matches.
> >
> > That won't help if you have to deal with branches back in time, but in
> > those cases, you can use touch to reset the .h file to an old date.
>
> That's neat.  If the hash is written to the file system (and into the
> Git repo), then it can be checked, and that would avoid a redo even
> after an initial checkout!
>
> If you do this, Attila, please let us know -- it might be a useful
> capability to generalize and put in the ASDF contribs.
> >
> > —♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics•
> > http://fare.tunes.org
> > The greatest lies always come in a thin coating of truth.
> >
> >
> > On Sat, Apr 17, 2021 at 4:44 PM Attila Lendvai
> > <attila.lendvai at gmail.com> wrote:
> >>
> >> thanks for the ideas Robert!
> >>
> >>>
> >>> I was wondering why it was important to avoid the build when the .h
> >>> file is newer than the .spec file. This shouldn't happen very often,
> >>> should it? Is it because:
> >>
> >>
> >> the problem is much more down to earth: generating the spec file
> >> requires launching a libllvm based external tool called c2ffi.
> >> compiling and properly configuring this tool can sometimes consume a
> >> day, and the users of e.g. hu.dwim.sdl shouldn't ever need to do
> >> that. it's only needed when you want to capture newly added artifacts
> >> from the SDL.h files.
> >>
> >> one way to avoid this could be to not communicate the dependency to
> >> ASDF, and make the .h -> .spec generation manual (this used to be the
> >> case). for some reason that feels lame, but not the end of the world
> >> either.
> >>
> >>> The .h file is getting refreshed too often by something upstream of
> >>> ASDF? E.g., is make being too eager about rewriting the .h file?
> >>
> >>
> >> the problem is not with too often, but with anything greater than
> >> zero, e.g. a git checkout.
> >>
> >> - attila