On Monday 06 September 2010, Ralf Wildenhues wrote: > Hello Stefano, > > * Stefano Lattarini wrote on Mon, Sep 06, 2010 at 05:06:23PM CEST: > > This patch fixes potential false negatives in the new tests. > > > > Internationalization tests: do not ignore failures. > > > > Some tests used the idiom: > > test $builddir = '.' || test ! -f posub/foo-bar.pot > > > > to check that a file is build in the source directory, not in > > the build directory. But even when the `errexit' shell flag > > is active, the above does not abort the script even if the file > > `posub/foo-bar.pot' exists, since the failing `test' is in a > > `||' compound command. Fix this problem by explicitly calling > > `Exit 1' where needed. > > I'm not sure I understand this rationale. The problem, as I see > it, is slightly different: with > > set -e > false || false > notreached > > it is portable to assume that the last line in the script is not > reached any more. That is, you can be sure that the script will > exit prematurely. Oh. Error on my part then: I erroneously thought that `false || false' wouldn't have caused the shell to exit even with `set -e'! Do you have a link to the relevant part of the POSIX standard dealing with `set -e', so that I can clear myself of other hideous misunderstandings?
AND: let's just drop this patch as useless, ok? > However, with this script: > > trap 'st=$?; exit $st' EXIT > set -e > true && false > notreached > > there is a problem with shells like Tru64 sh (and some others): > the false causes the shell to not execute the last line of the > script any more. However, the value of $? at the time the EXIT > trap is entered is still that of the 'true' command, so 0. Only > after the exit trap is finished, will the shell set $? to that of > 'false'. Problem is, the shell doesn't ever get to that point, > because the 'exit' within the trap causes it to, well, exit before > that, and with a status of $st which is 0. > > This is why autoconf.texi has the following bits, and > recommendation at the end: > > Portable scripts should not use `set -e' if `trap' is used to > install an exit handler. This is because Tru64/OSF 5.1 `sh' > sometimes enters the trap handler with the exit status of the > command prior to the one that triggered the errexit handler: > > $ sh -ec 'trap '\''echo $?'\'' 0; false' > 0 > $ sh -c 'set -e; trap '\''echo $?'\'' 0; false' > 1 > > Thus, when writing a script in M4sh, rather than trying to > rely on `set -e', it is better to append `|| AS_EXIT' to any > statement where it is desirable to abort on failure. > > The equivalent to `|| AS_EXIT' in the Automake testsuite is `|| > Exit 1'. > > That also means, that we should probably be more cautious with > removing `|| Exit 1' instances from tests. Why? The exit trap is currently not installed if a broken /bin/sh is detected, is it? > Or, here's a different idea: maybe we can somehow detect this shell > feature at run time. In that case it is sufficient to just *not* > exit from within the trap (unless the trap code has caused another > failure status that should be reported). What about my pending patch "Testsuite: use $SHELL to run tests which are shell scripts."? That should ensure that the tests are run with a decent shell. Maybe we could then hack Automake's configure.ac to ensure that configure reject shells exhibiting the trap bug. What is the status of ksh on Tru64/OSF 5.1? Is it as broek as /bin/sh, or is it usable for our purposes? Regards, and sorry for the botched patch. Stefano
