Re: expr ... and `expr ...` return different results on QNX 4.2.5

[Akim Demaille]

| Hello!
| > Yes.  I wouldn't bother doing that.  Just tell them to get a working
| > shell.  You have to draw the line somewhere.
| 
| That's correct. We cannot support command.com anyway :-)
| 
| > If you want to quote chapter and verse, you can tell them that
| > POSIX.2-1992 section 3.9.1 page 136 lines 755-759 says that x=`FOO`
| > must yield FOO's exit status.  Any shell that doesn't do this is
| > seriously broken.
| 
| That's not the autoconf's way. The autoconf's way is to find a better
| shell on that system, e.g. /bin/sh5 or /bin/ksh. If it fails then it's Ok
| for autoconf to fail.
| 
| But I still hope to work around those issues with QNX 4.25 somehow.
| How about this:
| 
| ac_output=`command || echo "===ERROR==="`
| case $ac_output in
|   *===ERROR===)
|     AC_MSG_ERROR([command failed]) ;;
|   *) ;;
| esac

This is atrocious :)

My personal opinion on this issue is that this feature is just too
essential and too primitive for us to try to work around it.  I'd say
`best effort', i.e., a *warning* is issued at the beginning, stating
that there might be problems because of the shell.  But let's give a
chance of running to configure.