Re: [eigen] any remaining issues blocking beta1, speak up!

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

Can you try compiling with

    -Wstrict-aliasing=1

indeed, the default value is 3, and 1 is the most aggressive warning
level. It could however report a lot of false positives. According to
`man gcc`.

Benoit

2010/7/3 Gael Guennebaud <gael.guennebaud@xxxxxxxxx>:
> here is a simplified version:
>
> #include <iostream>
> #include <Eigen/Dense>
>
> template<typename A, typename B> EIGEN_DONT_INLINE int foo(const A& a,
> const B& b)
> {
>  return (a - b).sum() <= 0;
> }
>
> int main()
> {
>  Eigen::Matrix<float,1,1> v;
>  v.setOnes();
>  return foo(v.colwise().maxCoeff(),v);
> }
>
> which, again, fails with gcc-4.3 + strict-aliasing only....
> investigating to see if I can find a workaround.
>
> gael
>
> On Sat, Jul 3, 2010 at 1:03 PM, Jitse Niesen <jitse@xxxxxxxxxxxxxxxxx> wrote:
>> On Sat, 3 Jul 2010, Benoit Jacob wrote:
>>
>>> All is in the title. Can we release beta1 this Saturday?
>>
>> There is also the stable_norm_1 test that is failing on gcc 4.3. This seems
>> to be a mistake in Eigen itself.
>>
>> See the previous email I wrote:
>>
>> On Thu, 1 Jul 2010, Jitse Niesen wrote:
>>>
>>> Date: Thu, 1 Jul 2010 11:02:51 +0100 (BST)
>>> From: Jitse Niesen <jitse@xxxxxxxxxxxxxxxxx>
>>> To: Eigen mailinglist <eigen@xxxxxxxxxxxxxxxxxxx>
>>> Subject: Failing stable_norm_1 test
>>>
>>> Hello,
>>>
>>> I just spent some time on the stable_norm_1 test, which fails on both my
>>> computer and Gael's computer when using gcc 4.3. It looks similar to the
>>> issue
>>> which you solved by the empty struct magic (well done!).
>>>
>>> The details are as follows. I constructed the following (fairly) minimal
>>> test
>>> example:
>>>
>>> #include <iostream>
>>> #include <Eigen/Dense>
>>>
>>> int main()
>>> {
>>>  Eigen::Matrix<float,1,1> v;
>>>  v(0,0) = 0.1;
>>>  std::cerr << "blue norm = " << v.colwise().blueNorm() << "\n";
>>>  std::cerr << "status = " <<
>>> v.colwise().hypotNorm().isApprox(v.colwise().norm(), 1e-4) << "\n";
>>> }
>>>
>>> When compiling with g++ (version 4.3.3) -O2 -g and running under valgrind,
>>> this
>>> produces:
>>>
>>> Use of uninitialised value of size 4
>>>    at 0x8048F28: bool
>>> Eigen::DenseBase<Eigen::PartialReduxExpr<Eigen::Matrix<float, 1, 1, 0, 1,
>>> 1>,
>>> Eigen::ei_member_hypotNorm<float>, 0>
>>> >::isApprox<Eigen::PartialReduxExpr<Eigen::Matrix<float, 1, 1, 0, 1, 1>,
>>> Eigen::ei_member_norm<float>, 0>
>>> >(Eigen::DenseBase<Eigen::PartialReduxExpr<Eigen::Matrix<float, 1, 1, 0,
>>> > 1, 1>,
>>> Eigen::ei_member_norm<float>, 0> > const&, float) const (in
>>> /scratch/1/users/jitse/work/c/eigen/eigenfoo)
>>>    by 0x8048AF5: main (in /scratch/1/users/jitse/work/c/eigen/eigenfoo)
>>>
>>> and the same error with the same stack trace a bit later, at 0x8048F2A.
>>>
>>> The result of the program is also wrong: it should print status = 1, but
>>> it
>>> says status = 0.
>>>
>>> The error goes away when compiling with -fno-strict-aliasing.
>>> I tried compiling with -Wstrict-aliasing=2 but that does not produce any
>>> warnings.
>>>
>>> Over to the gurus!
>>>
>>> Cheers,
>>> Jitse
>>>
>>
>>
>>
>
>
>