Re: texinfo 6.0 texindex problem?

[Gavin Smith]

On 9 October 2015 at 08:06, Eli Zaretskii <address@hidden> wrote:
> So perhaps we should introduce a facility for such tests, and
> preferably in a way that is itself backward-compatible, e.g., testable
> with @ifset or some such.

It already exists. See (texinfo)Testing for Texinfo Commands:

============
  These command-checking conditionals themselves were added in
Texinfo 5.0, released in 2013--decades after Texinfo's inception.  In
order to test if they themselves are available, the predefined flag
'txicommandconditionals' can be tested, like this:

     @ifset txicommandconditionals
     @ifcommandnotdefined foobarnode
     (Good, '@foobarnode' is not defined.)
     @end ifcommandnotdefined
     @end ifset

  Since flags (see the previous section) were added early in the
existence of Texinfo, there is no problem with assuming they are
available.
==============