GNU bug report logs - #7868
parallel-tests and command-line length limit issue

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Message #17 received at 7868 <at> debbugs.gnu.org (full text, mbox):

From: Ralf Wildenhues <Ralf.Wildenhues <at> gmx.de>
To: Stefano Lattarini <stefano.lattarini <at> gmail.com>
Cc: 7868 <at> debbugs.gnu.org
Subject: Re: bug#7868: splitting up test suites
Date: Thu, 20 Jan 2011 20:41:10 +0100

Hi Stefano,

* Stefano Lattarini wrote on Thu, Jan 20, 2011 at 12:38:17PM CET:
> On Wednesday 19 January 2011, Ralf Wildenhues wrote:
> > We've finally reached the point where we have more than 1000
> > tests, $(TESTS) expands to 15k characters, and where 'make check' will
> > not work at all any more on MSYS, because it cannot spawn sh any more,
> > presumably in 'make check TESTS="..."'.  (MSYS make doesn't export
> > macros to the environment of spawned processes even without .NOEXPORT,
> > presumably otherwise lots of Makefiles would be really unusable here.)
> > This also clears up the spurious failure of sed a few days ago.
> >  
> > Here's a preliminary plan for multiple testsuites per Makefile.am.
> >
> Hmmm... while this feature might be worth having even indipendently
> from the issue at hand (but see below for small nits), I still think
> that in the long run it would be nicer to transparently work around
> such command-line length issues in the test driver, if possible.

No, that is not possible with portable make.

> Do
> you think your patch "parallel-tests: avoid command-line length limit
> issue" (from commit v1.11-191-g24e3b4e) could be resurrected in some
> way?

No.  It is fundamentally flawed.  Here's why: while it may fix things at
the level of recursion below that, eventually the rule commands which
were changed in that patch will fail to execute, because they pose too
long a command line for the shell.

There simply is no way to get things to scale except by using GNU make
specifics, or splitting long lists of files up manually.  Well, an
external list of files to be read in could work, but then we don't have
make semantics easily available.

In that light, I'm sorry you already wrote the patch you did, because I
don't see how it can improve things significantly.  I didn't try the
patch or look in detail, please ping me if you still want me to do that.

> > It would be nice if this worked somehow:
> > 
> > # These are all specified by the user:
> > TEST_SUITE_LOGS = suite1.log suite2.log suite3.log ..
> > TEST_EXTENSIONS = .test ...
> > # these undergo $(EXEEXT) autoexpansion internally:
> > suite1_log_SOURCES = all.test aclocal7.test ...
> > suite2_log_SOURCES = suffix.test ...
> >
> What about using `TESTS' instead of `SOURCES' in these two last variables?
> That would seems more natural to me, especially considering the API of the
> current parallel-tests driver.

First off, it would make sense to review the several discussions we had
about this back when parallel-tests was implemented (more precisely,
ported from Akim's GNU make-specific implementation).  See e.g.,
http://thread.gmane.org/gmane.comp.sysutils.automake.patches/3225
http://thread.gmane.org/gmane.comp.sysutils.automake.general/8063

The idea was to treat tests as we treat compiled languages:
.c files are sources for programs but get turned into .o files.
Here, .test files are sources for testsuite logs, but the intermediates
are the per-test .log files.  And there's maybe the unification of
suite*.log's to a final log on top of that.

If we can handle the latter via automake's register_language machinery,
then putting tests in *_SOURCES variables would be fairly natural.

OTOH, you are right in that elsewhere, _SOURCES are usually meant to be
final, nonderived files, which doesn't fit the picture here.  So maybe
suite1_log_TESTS is more appropriate after all.

> OTOH, would that maybe make the implementation more difficult?

Not if it's like the current implementation, no.

> I think it would also be nice to generate separate check/recheck targets
> for each testsuite; for example, "make check-suite1" could run all the
> tests in $(suite1_log_SOURCES), and "make recheck-suite2" could re-run
> all the tests in $(suite2_log_SOURCES) that failed (or xfailed) in the
> previous run.
> 
> Hmm... No, wait, it would be even nicer to allow the user choose which
> testsuite(s) to run by resetting the $(TEST_SUITE_LOGS) variable:
> 
>   make check TEST_SUITE_LOGS='suite1.log suite2.log'
> 
> Which makes me think that, perhaps, a variable like $(TEST_SUITES) would
> be preferable:
> 
>   make check TEST_SUITES='suite1 suite2'
> 
> but then the API should be changed to something like:
> 
>  # These are all specified by the user:
>  TEST_SUITES = suite1 suite2 suite3 ..
>  TEST_EXTENSIONS = .test ...
>  # these undergo $(EXEEXT) autoexpansion internally:
>  suite1_TESTS = all.test aclocal7.test ...
>  suite2_TESTS = suffix.test ...
> 
>  # These are then produced by automake:
>  TEST_SUITE_LOGS = $(TEST_SUITES:=.log)
>  TEST_SUITE_HTMLS = $(TEST_SUITES:=.html)
>  suite1_LOGS = $(am__helper_var:.test=.log)

Unfortunately, this is error-prone, because some GNU make versions
expand
  empty =
  TEST_SUITES = foo $(empty)
  TEST_SUITE_LOGS = $(TEST_SUITES:=.log)

into `foo.log .log' rather than `foo.log '.  This happens in practice
if `empty' is set only under some Automake conditional, as in
  if COND
  TESTS += bar
  endif

That is the reason the check-TESTS rule is so ugly (and recursive) in
the first place.  I really would like to avoid more instances of this
wart; so specifying files without extension is Not Good(TM).

Separate check/recheck targets are of course nice, but IMVHO optional
for the first iteration.

> > In the <suite>_SOURCES, $(EXEEXT) transformation should take place
> > (unless no-exeext is given, of course), just as is currently done for
> > TESTS and *_PROGRAMS.  Hmm, alternatively we could also require all
> > <suite>_SOURCES to be listed in $(TESTS), that would allow reuse of
> > this variable as well, at the cost of some specification redundance.
> >
> 
> > Open questions: how to produce nice results, both on stdout and in suite
> > log files.  One way is to merge all logs into a final TEST_SUITE_LOG
> > (that way we could also reuse that variable).  Another is to try to even
> > hide the summaries of the individual suites, iff a final suite is being
> > made.
> >
> These both sound sensible.  Another problem is how to avoid that, in a
> parallel make run, the summary from a testsuite gets mixed and garbled
> with the output/summary from another testsuite, as in e.g.:

Yes.  We definitely want to be able to run tests from different
testsuites in parallel.  So some form of partial summary hiding is
prudent; I hope we can achieve that without yet another make
indirection, but I'm not optimistic.

Thanks for the feedback,
Ralf

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