Re: _AS_ECHO_N_PREPARE - bug correction in ksh88 on AIX 6.1

[Ralf Wildenhues]

* Eric Blake wrote on Sat, Jun 27, 2009 at 04:01:15PM CEST:
> According to Ralf Wildenhues on 6/25/2009 9:18 PM:
> > * Jan Madzik wrote on Thu, Jun 25, 2009 at 06:48:37PM CEST:
> >> I found bug in korn shell (version M-11/16/88f) on AIX 6.1 (tested
> >> only on one server instance) and due to this bug I couldn't correctly
> >> configure ImageMagick.
> > 
> > Confirmed on AIX 5.3, thanks for the bug report.
> > 
> > This patch should be sufficient to fix this instance of the bug, but
> > it's still lacking a testsuite and documentation addition.
> 
> So how exactly do you describe the bug?  Using 'echo \c' inside a command
> substitution corrupts state until the next command substitution echo?

Yes, I think that's what it is.

> When this bug is detected, is it better to just try an alternate means for
> printing text without a newline, such as printf, rather than trying to
> audit all uses of echo \c?

I audited all uses of ECHO_C in Autoconf, Automake, Libtool, and gnulib,
and found no problematic instances.  I suppose it should be sufficient
to recommend to use AS_ECHO_N within scripts, which is what Autoconf
does already mostly.  Within makefile snippets, an added
  ; echo >/dev/null

should be a suitable workaround, I guess.  More generally though, I'd
be wary of uses of ECHO_C within command substitutions, as the
substitution will strip off a trailing newline anyway, so it shouldn't
be a wide-spread problem.

Cheers,
Ralf