Qhull and scripts/geometry

[Jaroslav Hajek]

On Tue, Feb 3, 2009 at 10:45 AM, Petr Mikulik <mikulik at physics.muni.cz> wrote:
>> >> | Yes; configuring Qhull with
>> >> |     CFLAGS="-fno-strict-aliasing -O2" ./configure $*
>> >> | does not crash the testing command
>> >> |      rbox c D3 | qconvex s G
>> >> |
>> >> | Could Octave's ./configure test the Qhull library? I propose that if the
>> >> | above test command (or some C++ source test case) crashes, then Octave does
>> >> | not link to Qhull library and writes a hint like
>> >> |   Crashing Qhull found; please recompile the Qhull library by
>> >> |     CFLAGS="-fno-strict-aliasing -O2" ./configure; make
>> >>
>> >> Can you provide an autoconf macro that does the test and does not
>> >> require an external program?  My Debian sysstem has the library but
>> >> the test programs are not installed.
>> >>
>> >> There is also the issue that running test programs limits the
>> >> usefulness of configure scripts when cross-compiling.  In this case, I
>> >> guess we would just have to assume that the library works when cross
>> >> compiling.
>> >
>> > I've prepared the shortest code that leads to crash if the Qhull library has
>> > been compiled without the appropriate CFLAGS.
>> >
>> > Usage:
>> >    gcc -o QhullCrashTest QhullCrashTest.c -lqhull -lm
>> >    echo "2 4 -0.5 -0.5 -0.5 0.5 0.5 -0.5 0.5 0.5" | ./QhullCrashTest
>> >
>> > If it crashes, nothing is written on stdout.
>> > If it does not crash, an "OK message" is written on stdout.
>> >
>> > Could this testing program be used in the Octave configure?
>> > I don't know how to write an autoconf macro for it.
>> >
>>
>> Hi Petr,
>>
>> I'll take care of the inclusion into configure. However, for best
>> suitability for autoconf macros (AC_RUN_IFELSE), please modify the
>> test program in the following manner:
>> 1. make the inputs part of the source
>> 2. indicate success by returning exit code zero. If you can do it, to
>> make the test more complete, I suggest also to check the results for
>> correctness (if a crash doesn't happen on some system, but instead
>> incorrect results are produced).
>
> I have no idea how to put the input data into the testing program.
>

I have taken a quick look at it and it seems the attached source is
able to reproduce the crash. Would you please verify with your
configuration?


> The success is indicated by zero exit code ("return 0"); failure is
> indicated by crash with a "Segmentation fault" ... the return value seems to
> be 139.

Yes, this is indicated by the system (and autoconf macro handles it).
I am, however, very suspicious about regarding a segfault as something
predictable; it depends on the OS and perhaps other circumstances.
It would be even better to check the results for correctness (see, for
instance, the analogous checks for correctness of BLAS library called
from Fortran); still, I'd be happy even with this. I'll turn this into
a patch.

cheers

-- 
RNDr. Jaroslav Hajek
computing expert
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz
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