Subject: bug#9245: FreeBSD make in concurrent mode report spurious success in automake-generated tests harness

From: Eric Blake <[email-masked]>
Date: Tue, 16 Aug 2011 10:18:51 -0600

On 08/16/2011 10:04 AM, Stefano Lattarini wrote:
> The "proper fix" is even easier BTW: just use "$$exit || exit 1" instead.
>
> The updated patch should now work (and I've tested it properly this time).
> This new patch hasn't been derived by "cargo-cult guessing", but from the
> explanation of the relevant FreeBSD make bug provided by Jilles Tjoelker:
>   <http://www.freebsd.org/cgi/query-pr.cgi?pr=159730>
>
> Now that's something to be documented in the Autoconf manual I'd say ...

Indeed.  So it all boils down to BSD make rewriting rules (but only for 
make -j) to be roughly:

sh -c 'set -v; your rules; set +v'

and losing your exit status (not to mention sharing shell status between 
commands that are supposed to be in independent shells), when it really 
should have been rewriting as something more complex:

sh -c '(your rule 1); (your rule 2); st=$?; set +v; exit $st'

And your workaround of an explicit exit rather than relying on $? at the 
end of your 'set +e' invocation is indeed the proper way to force the 
parallel make bug to be avoided, by exiting prior to any post-commands 
injected by the BSD make rewriting going on that corrupt $?.

-- 
Eric Blake   [email-masked]    +1-801-349-2682
Libvirt virtualization library http://libvirt.org