Re: Broken makefile given Autoconf version mismatch

[Keith Marshall]

On Wednesday 12 April 2006 8:47 pm, Stepan Kasal wrote:
> On Wed, Apr 12, 2006 at 08:45:04PM +0200, Ralf Wildenhues wrote:
> > here's a patch that I think does more or less what Bruno's patch
> > intends to do, against current CVS.
>
> I worked on the same issue.  We both use the same pattern
>         `sed -n '/@datadir@/p;/@docdir@/p;/@infodir@/p...' ...`

I'd like, if I may, to sound a note of caution concerning this sed 
command syntax: the use of semicolons as command separators in the sed 
script is an implementation dependent extension, which is not portable.  
On some platforms, the test using this sed syntax *will* fail, not 
because the feature you are testing is unsupported, but because the test 
itself is invalid.

In November 2005, Robert Goulding posted these bug reports on 
address@hidden:
http://lists.gnu.org/archive/html/groff/2005-11/msg00004.html
http://lists.gnu.org/archive/html/groff/2005-11/msg00074.html

It turns out that Robert was having a problem building CVS groff,
which requires texinfo >= 4.8 to compile the info files, under Mac OS X, 
and configure was saying his texinfo was too old, in spite of him having 
explicitly just installed texinfo-4.8.  The actual problem was that the 
configure test employed a sed command with this same semicolon usage,
and was not behaving as expected -- the test failed because *it* was 
invalid, *not* because the detected texinfo was too old!

At this time, I checked the man page for sed on a SunOS box.  Here the 
documentation very explicitly states that commands in sed scripts *must* 
be separated by newlines; semicolon is acceptable as an alternative to a 
comma, to separate the two components of a range specification, but it is 
*not* acceptable as a command separator.  Curiously, the SunOS sed 
implementation *does* support semicolons as command separators, even 
though the man page expressly excludes it; it would seem, however, that 
Mac OS X may be more rigorous in this requirement.

To guarantee portability of the above sed command, it cannot be written 
as shown:

    `sed -n '/@datadir@/p;/@docdir@/p;/@infodir@/p...' ...`

it *must* be rewritten as:

    `sed -n -e '/@datadir@/p' -e '/@docdir@/p' -e '/@infodir@/p' ...`

or as:

    `sed -n '/@datadir@/p
             /@docdir@/p
             /@infodir@/p
             ...' ...`

(i.e. with explicit newlines separating the sed command strings).

Regards,
Keith.