Relativising FASL Cache Paths

[Faré]

Source location via logical pathnames works great on CCL. However, on SBCL,
they run afoul of SBCL's strict enforcement of the standard limitations to
logical pathnames, and you will have quite a hard time with them if you
succeed at all.

One easy but fragile and ugly way to make it work with SBCL would be to
fake logical pathnames using a fixed symlink in $TMPDIR.

More correct solutions that require more hacking include: adding an extra
argument to compile-file by hacking both SBCL and ASDF, to let you override
the default source location stored in a file; or maybe if you're hacking
SBCL, add a non standard logical pathname option. Etc.

My recommendation would be to strive to upstream your patch to whichever
software you hack, and to that end, to speak with the maintainers about
what they're willing to commit.

-#f

On Fri, Dec 15, 2017, 07:32 Nicolas Hafner <shinmera at tymoon.eu> wrote:

> I see, thanks a lot for the hint.
>
> I've just stumbled upon another complicating factor though, which is
> source location information. Apparently it is not possible to manually
> relocate source information after it has been loaded from a FASL in SBCL.
> However, if the Lisp files were compiled using a logical pathname, logical
> pathname translations could be used to fix that up as required.
>
> Is there a way to transform the input/output files to logical pathnames to
> facilitate this, or would that be too much to ask for?
>
> On 15/12/17 11:44, Faré wrote:
>
> The design of ASDF is that you should properly initialize the
> output-translations. The usual way is to use
> ~/.config/common-lisp/asdf-output-translations.conf, but since in your
> case you support the directory moving from one instantiation to the
> next, it is probably better to call
> asdf:initialize-output-translations at startup with a proper argument
> (using properly computed absolute pathnames), just after you (require
> "asdf") (which I assume is possible and yielding no older than 3.1.2)
> but before you compile anything with it. Untested template that might
> work:
>
> (asdf:initialize-output-translations
>   `(:output-translations
>       (,(uiop:wilden *portacle-directory*) ,(uiop:wilden
> (uiop:subpathname *cache-top* "portacle/")))
>       (t (uiop:wilden (uiop:subpathname *cache-top* "other/")))
>     :ignore-inherited-configuration))
>
> Note that you may choose to use the :inherit-configuration instead.
>
> —♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org
> If soldiers are not to cross international boundaries, goods must do so. Unless
> the Shackles can be dropped from trade, bombs will be dropped from the sky.
>         — Otto T. Mallery
>
>
> On Fri, Dec 15, 2017 at 4:41 AM, Nicolas Hafner <shinmera at tymoon.eu> <shinmera at tymoon.eu> wrote:
>
> Hello everyone.
>
> I have a rather particular problem that I have so far not been able to solve
> on my own without brittle workarounds. Specifically, I'm looking for a way
> to ensure that the directory paths stored in the FASL cache directory are,
> if possible, truncated according to some other path (by enough-pathname or a
> similar facility).
>
> The reason I want this is for Portacle. The Portacle directory should be
> relocatable and you should even be able to take it with you on a flash drive
> to run on other machines. However, this usually means that the absolute
> position of the directory on the file system will change, even if the Lisp
> files and FASLs within it remain at the same relative locations.
>
> I would thus like to stop ASDF from recompiling everything when the
> directory is moved absolutely, and instead rely on paths relative to
> Portacle's own "root" directory if possible.
>
> My current approach involves setting
> asdf/output-translations::*output-translation-function* to a modified
> version that attempts to relativise the path as seen here. However, this
> sometimes leads to issues as the translated path might be relative and other
> components down the line seem to expect absolute paths.
>
> Any advice on how to proceed on this would be appreciated.
>
> Sincerely, Nicolas Hafner
>
>
>
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