Shell comments in make rules (was: backcompat5.test: avoid '##'-style comments inside recipe commands)

[Stefano Lattarini]

On Tuesday 16 November 2010, Ralf Wildenhues wrote:
> * Stefano Lattarini wrote on Mon, Nov 15, 2010 at 11:57:14PM CET:
> > On Monday 15 November 2010, Ralf Wildenhues wrote:
> > > * Stefano Lattarini wrote on Sun, Nov 14, 2010 at 11:00:16PM CET:
> > > >  <http://autobuild.josefsson.org/automake/log-201011141902490189000.txt>
> > > 
> > > > > FAIL: backcompat5.test (exit: 1)
> > > > > ================================
> > > > >
> > > > [CUT]
> > > > > find ../foo-1.0 -print ## useful for debugging
> > > > > find: missing conjunction
> > > > > *** Exit 1
> > > > > Stop.
> > > > Seems like a limitation (bug) of the find utility; what I'd do is
> > > > replacing the above find command simply with:
> > > >   find ../foo-1.0
> > > > WDYT?
> > > 
> > > I think the comment is taken as part of the command.
> > Hmm... that's an automake comment: shouldn't automake strip it?
> 
> Quoting automake.info:
> 
>      Automake also allows a form of comment that is _not_ copied into the
>   output; all lines beginning with `##' (leading spaces allowed) are
>   completely ignored by Automake.
> 
> Letting automake strip '##.*' within recipe commands is not safe, if we
> acknowledge that some makes obey decent quoting semantics (keeping '#'
> inside single- or double-quoted strings) and the user may rely on that.
That makes definitely sense; sorry for my stupid misunderstanding.
Oh well, at least I've learnt something new today.

> > But even if it doesn't, shouldn't the comment in question be consired
> > a shell comment anyway?  If that's not the case, well, I'd regard this
> > behaviour as a severe bug in the OSF make implementation.
> 
> Yes, and it is quite well documented in
>   info Autoconf 'Comments in Make Rules'
But that only says:
 "Some make treat anything starting with a tab as a command for the
  current rule, even if the tab is immediately followed by a #."
which is not relvant for the current situation.  And BTW, if I'm not
mistaken, Automake warns about that unportability (which is why I
managed to avoid it in many if not all my previous patches).

Regards,
  Stefano