weird compile errors when setting -DCMAKE_CXX_STANDARD=17

Beginner Questions
1

gcc-10 on ubuntu 18.04

When the python wrappers are selected be built and CMAKE_CXX_STANDARD=17 I get weird error about type_traits way down low in the c++ standard library. I think it has to do with the python bindings may be hard coding std=c++11.

I am not totally sure I understand what the issue is, but gives and error like

_Tp  does not refer to a value 
// referencing this code snippet  in type_traits
: public integral_constant<bool, _GLIBCXX_BUILTIN_IS_SAME_AS(_Tp, _Up)>

there were some other issues around throw(itk::object) which I replaced with noexcept(false) but that didn’t seemed relevant to the issue above.

I also turned off the python bindings and it appears to be compiling fine.

2

SWIG’s docs say:


 work has only just begun on adding C++17 support. SWIG-4.0.0 is the first version to support any C++17 features.

1 Like
3

that is very helpful, from pursuing it looked like itk should compile with 17 just fine, but didn’t think about it interfering with swig wrapping.

4

it appears to give the same error when CMAKE_CXX_STANDARD is not set. which I would assume get set to a default?

the latest cmake sets it to 14, which appears to be the same issue.

also I believe I am compiling with swig 3.x (the default), maybe using external 4.x would fix. Is it in the works to upgrade swig to 4.x in the default build settings?

I found that the default build uses swig 3.x on unix. after modifying to use 4.x the build produces the same issue.

5

Hi @kayarre,

How was gcc-10 installed? I would like to reproduce the issue.

Thanks,
Matt

6

on Ubuntu 18.04 I used the apt repo ubuntu-toolchaing-r/test

apt install gcc-10 g+±10 gfortran-10.
Kurt

1 Like
7

Thanks, Kurt. I was able to reproduce the error.

This patch addresses the build errors:

We use CastXML to parse the C++ headers to generate the wrapping interface. CastXML uses LLVM for syntax parsing. This version bumps LLVM from 6 to 10 to improve syntax support for GCC 10.