*LOAD-TRUENAME* and ASDF

[Robert Goldman]

On 8/31/16 Aug 31 -11:26 AM, Kevin Layer wrote:
> Jason Miller wrote:
> 
>>> On 09:48 Mon 29 Aug     , Kevin Layer wrote:
>>>> I've avoided getting into this discussion, but I feel I need to ask:
>>>> why use *load-truename* instead of *load-pathname*?
>>>>
>>>> *load-truename* goes through symbolic links (even though the ANS says
>>>> nothing about it, this is the behavior of implementations I know of)
>>>> and that is almost always the wrong thing.  GNU make doesn't do it, I
>>>> don't see why ASDF should do it.  A build system should never itself
>>>> follow symlinks, because it defeats systems that have been in place
>>>> for 30+ years: linked directories of binary files linking to a single
>>>> source directory.
>>> Somewhat off-topic, but I'll bite:
>>>
>>> This is because *load-pathname* is likely to be a relative
>>> pathname, ..
> 
> This is certainly not true in Allegro.  In lisps where it is true,
> it's easily fixable with (merge-pathnames *load-pathname*).
> 

I suppose this is safe, but I always have an unpleasant feeling about
using a function call like this that depends on the value of a special
variable (*default-pathname-defaults*) that I don't control.

At any rate, we pretty much established that in an ASDF-loaded system,
*load-pathname* is likely to be garbagy, because at load time it
typically holds the pathname of the *RELOCATED* FASL file, which is of
no use to anyone.

best,
r