Re: to conditionally test, or not to conditionally test?

[Keith MARSHALL]

Stepan Kasal wrote:
> It's hard to tell whether a macro calls AC_REQUIRE.  (It can call it
> indirectly.)
>
> A real fix will be to use shell functions to reimplement AC_REQUIRE,
> in autoconf-3.

Are you now saying that shell functions are safe to use in a portable
fashion?  That would contradict the advice given in "info autoconf",
node "Portable Shell":--

>      You should not use shell functions, aliases, negated
>   character classes, or other features that are not found in all
>   Bourne-compatible shells; restrict yourself to the lowest common
>   denominator.

In this same paragraph, I also see the advice:--

>   Also, include a space after the exclamation point in interpreter
>   specifications, like this:
>
>      #! /usr/bin/perl
>
>   If you omit the space before the path, then 4.2BSD based systems
>   (such as DYNIX) will ignore the line, because they interpret `#! /'
>   as a 4-byte magic number.

I recently queried this advice, in respect of its application in the
groff project, and was advised that it is nonsense.  I posted that
response here, but as yet have seen no comment.

If such advice in autoconf documentation truly is nonsense, then should
it not be expunged?

Best regards,
Keith.