Eigen MSVC warnings C4348 "redefinition of default parameter"

[SimonRit]

Description

Since the recent updates of Eigen (#4265 according to the dashboard), I get many warnings from Eigen's code with MSVC. The warning code is C4348.

Steps to Reproduce

Compile ITK with MSVC 19.27.29111.0

Expected behavior

No warnings.

Reproducibility

100%

Versions

ITK master

Environment

MSVC 19.27.29111.0

Additional Information

See nightly build of RTK: https://my.cdash.org/index.php?project=RTK.

[thewtex]

CC @phcerdan

[phcerdan]

@SimonRit thanks for the report. Is that a newer MSVC? I didn't see those warnings in the PR.

Not sure if that warning is meaningful for Eigen.
Could you try disabling it?
Add 4348 in that line:
https://github.com/phcerdan/ITK/blob/fix_metadataobject_print/Modules/ThirdParty/Eigen3/src/itkeigen/Eigen/src/Core/util/DisableStupidWarnings.h#L23

Maybe it's worth to raise an issue upstream https://gitlab.com/libeigen/eigen/-/issues.

[SimonRit]

Is that a newer MSVC?

No, it's MSVC 2019.

Could you try disabling it?

It does remove the warnings. Should that be an ITK PR or should it be an Eigen PR?

[phcerdan]

Good question, Being an old compiler, and not already solved upstream, I think this would be a patch (from ITK) in our fork of Eigen. I will patch it and update ITK.

[N-Dekker]

According to https://godbolt.org/z/PExefEfzW the warning may still be produced by the latest version of MSVC!

template <class T=int> struct A;   // forward declaration
template <class T=int> struct A { };

Does that mean that it should be solved upstream?

[phcerdan]

Why are we not picking it up in our CI then?

[phcerdan]

Please, open it up upstream if you can reproduce it, I don't have access to MSVC.

[N-Dekker]

For my understanding, do these warnings specifically occur when the ITK CudaCommon module is enabled?