error: in-class initializer for static data member of type 'const double' requires 'constexpr' specifier

[yurivict]

Build fails with clang-6 on on FreeBSD:

../../../../../src/lib/chemistry/qc/mbptr12/transform_tbint.h:64:23: error: in-class initializer for static data member of type 'const double' requires 'constexpr' specifier
      [-Wstatic-float-init]
  static const double zero_integral = 1.0e-12;
                      ^               ~~~~~~~
../../../../../src/lib/chemistry/qc/mbptr12/transform_tbint.h:64:3: note: add 'constexpr'
  static const double zero_integral = 1.0e-12;
  ^
  constexpr 

[yurivict]

You need to specify -std=c++98.

[evaleev]

this is version 2.3.1?

[yurivict]

Yes, this is version 2.3.1?

Is this the latest version?
The releases page has a recent tag release-1-0 for some reason.