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

[Akim Demaille]

>>>>> "Pavel" == Pavel Roskin <address@hidden> writes:

>> > b=`false` || echo Ok > > It should print "Ok". If it doesn't, we
>> are in trouble.
>> 
>> We are in trouble - no response.

Pavel> :-(

I concur.


Pavel> Well, one consequence is that some errors will not be
Pavel> detected. For example, missing Makefile.in will not be
Pavel> reported. 

Exactly :(

Pavel> It's a "developer error", i.e. it shouldn't happen with
Pavel> packages that came through "make distcheck", however I don't
Pavel> feel good about it.

Same here.  I wonder how many times we depend upon this in configure.
Without looking at the sources I can only think about the same example
as you do.

Pavel> I don't know how many times we rely on similar
Pavel> constructs. There may be more serious problems. To fix them, we
Pavel> should never use $? after _any_ assignments.

That's really bad in theory, I hope its impact is not too strong.  For
instance in the case you mention, the error message is still
displayed, which softens the issue.

Pavel> I don't see any other way to get the output and the exit status
Pavel> from a the same command without using temporary files or sed or
Pavel> set + for loop.  Anybody knows how to rewrite this:

Pavel> ac_output=`command`; ac_status=$?

Pavel> in a way that it works even on QNX but doesn't cause
Pavel> significant slowdown?

ac_output=`command; echo $? >confstat`; ac_status=`cat confstat`

?  Gross.