Re: [eigen] can't reproduce gcc 4.3.4 errors

[Benoit Jacob <jacob.benoit.1@xxxxxxxxx>]

anyway, it sounds like either Eigen or some of its unit tests are
unsafe wrt strict aliasing!!

If it's Eigen itself, we have no choice but to fix that, since strict
aliasing is part of -O2 in gcc...

Benoit

2010/6/29 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
> hehe, this sounds like the problem that Sune had the other day on IRC. CC'ing.
>
> Benoit
>
> 2010/6/29 Gael Guennebaud <gael.guennebaud@xxxxxxxxx>:
>> hm,
>>
>> -O2 -fno-strict-aliasing (and removing the hardcoded -fstrict-aliasing
>> from our cmakefile)
>>
>> 100% tests passed, 0 tests failed out of 453
>>
>> much better.
>>
>> gael
>>
>> On Tue, Jun 29, 2010 at 10:55 AM, Gael Guennebaud
>> <gael.guennebaud@xxxxxxxxx> wrote:
>>> ok here,  with -O2 -fno-guess-branch-probability, 4 tests fail as follow:
>>>
>>> guenneba@devel10:~/eigen/build/test> ./array_2
>>> Initializing random number generator with seed 1277801661
>>> Repeating each test 10 times
>>> Test comparisons(Array22f()) failed in
>>> "/home/guenneba/eigen/test/array.cpp" (136)
>>>    test_ei_isApprox(((m1.abs()+1)>RealScalar(0.1)).colwise().count(),
>>> ArrayOfIndices::Constant(cols,rows).transpose())
>>>
>>> guenneba@devel10:~/eigen/build/test> ./array_3
>>> Initializing random number generator with seed 1277801662
>>> Repeating each test 10 times
>>>
>>>    actual   = 2.66729
>>>    expected = 2.53391
>>>
>>>
>>>    actual   = 1.17816
>>>    expected = 1.93492
>>>
>>>
>>>    actual   = -2.79358
>>>    expected = -0.758141
>>>
>>>
>>>    actual   = -2.06046
>>>    expected = -2.54951
>>>
>>>
>>>    actual   = -1.27569
>>>    expected = 0.919771
>>>
>>>
>>>    actual   = 5.67633
>>>    expected = 4.85775
>>>
>>>
>>>    actual   = -5.2517
>>>    expected = -3.85892
>>>
>>>
>>>    actual   = -1.33353
>>>    expected = -0.700732
>>>
>>>
>>>    actual   = -3.33972
>>>    expected = 0.721723
>>>
>>>
>>>    actual   = -1.61675
>>>    expected = 0.256261
>>>
>>> Segmentation fault
>>>
>>> guenneba@devel10:~/eigen/build/test> ./geo_hyperplane_4
>>> Initializing random number generator with seed 1277801668
>>> Repeating each test 10 times
>>> Segmentation fault
>>>
>>> guenneba@devel10:~/eigen/build/test> ./geo_parametrizedline_4
>>> Initializing random number generator with seed 1277801673
>>> Repeating each test 10 times
>>> Segmentation fault
>>>
>>>
>>> gael
>>>
>>> On Tue, Jun 29, 2010 at 10:29 AM, Hauke Heibel
>>> <hauke.heibel@xxxxxxxxxxxxxx> wrote:
>>>> Ok, I can try to run the complete tests too. Here are also the flags I
>>>> used to run (so far just a few of) the failing tests.
>>>>
>>>> CXX:               /usr/bin/c++-4.exe
>>>> CXX_VERSION:       c++-4 (GCC) 4.3.4 20090804 (release) 1
>>>> CXX_FLAGS:          -Wnon-virtual-dtor -Wno-long-long -ansi -Wundef
>>>> -Wcast-align -Wchar-subscripts -Wall -W -Wpointer-arith
>>>> -Wwrite-strings -Wformat-s
>>>> ecurity -fexceptions -fno-check-new -fno-common -fstrict-aliasing
>>>> -Wno-variadic-macros -Wextra -pedantic
>>>>
>>>> - Hauke
>>>>
>>>> On Tue, Jun 29, 2010 at 10:25 AM, Gael Guennebaud
>>>> <gael.guennebaud@xxxxxxxxx> wrote:
>>>>> On Tue, Jun 29, 2010 at 10:14 AM, Hauke Heibel
>>>>> <hauke.heibel@xxxxxxxxxxxxxx> wrote:
>>>>>> On Mon, Jun 28, 2010 at 11:15 PM, Gael Guennebaud
>>>>>> <gael.guennebaud@xxxxxxxxx> wrote:
>>>>>>> I believe there is a bug in gcc, here is the related bug report:
>>>>>>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42255
>>>>>>> but no fix yet.
>>>>>>
>>>>>> That means we can get rid of the errors by disabling -fprofile-arcs?
>>>>>
>>>>> A while ago, such errors appeared only with  -fprofile-arcs, i.e.,
>>>>> when coverage testing was enabled. But now, even without
>>>>> -fprofile-arcs we hit these weird errors. After some investigations, I
>>>>> found that disabling the guess-branch-probability optimization that is
>>>>> automatically enabled with -O2 solved a couple of errors:
>>>>>
>>>>> -O2 -fno-guess-branch-probability
>>>>>
>>>>> Actually, guess-branch-probability and -fprofile-arcs seems to be
>>>>> quite related. I've updated the bug report with that respect, but news
>>>>> so far.
>>>>>
>>>>> I'm currently compiling with -O2 -fno-guess-branch-probability to see
>>>>> if there remain other errors....
>>>>>
>>>>>
>>>>> gael
>>>>>
>>>>>> - Hauke
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>
>>
>>
>