Subject: bug#24471: 25.1.50; Error on empty PATH component

From: Achim Gratz <[email-masked]>
Date: Mon, 17 Oct 2016 20:16:17 +0200

Eli Zaretskii writes:
> You must re-dump Emacs for this to take effect.

Ah, OK.  I had hoped that re-loading the changed files would do it, but
no dice.

> Anyway, the change that was committed is different, so the above is no
> longer pertinent.
>
> (I don't think I understand what you meant by your comment about "nil
> meaning default-directory being wrong for PATH and POSIX".)

POSIX specifically prescribes that an empty PATH element equals "." and
declares that a legacy feature that strictly conforming applications
shall not use, but in other environment variables an empty path element
is also allowed and replaced by different defaults.  For NLSPATH that
default is %N and for MANPATH it usually means some system-defined
(POSIX doesn't mention that possibility).

Whether default-directory equates "." seems to depend on when it gets
evaluated, since it's normally set to some absolute path.  So a textual
replacement with "." seems more correct than some hand-waving about nil
representing current-directory in the case of PATH.  OTOH, if other
environment variables are intended to get processed by parse-colon-path,
then that replacement would need to be different for each such variable.

Regards,
Achim.
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