Re: [Vxl-maintainers] why not...vul_arg and required arguments

[Gehua Y. <yan...@gm...>]

Hi Antonio,

I am having a small trouble compiling with the new vul_arg.h.   Visual
Studio raised a warning:

Warning    75    warning C4661: 'vul_arg<T>::required_option_type
vul_arg<T>::is_required' : no suitable definition provided for
explicit template instantiation request
c:\vxl\src\core\vul\vul_arg.h    198

and eventually a linking error:

Error    495    error LNK2001: unresolved external symbol "public:
static struct vul_arg<int>::required_option_type
vul_arg<int>::is_required"
(?is_required@?$vul_arg@H@@2Urequired_option_type@1@A)
C:\vxl\bin-vc10-x64\core\vul\tests\test_arg.obj


A fix is to add this line to initialize the static member variable
outside of class scope:

  template <class T>
  typename vul_arg<T>::required_option_type vul_arg<T>::is_required;  // init


However, I do not like this fix as it may potentially result in
duplicate symbol error at linking stage if two different source files
use vul_arg with the same type.  I would propose to use a slightly
different version:
static required_option_type is_required() { return required_option_type(); }


Let me know whether you are okay with this solution.


Best Regards,
Gehua Yang







Regards,
Gehua Yang





On Fri, Mar 30, 2012 at 10:52 AM, Antonio Garrido Carrillo
<A.G...@de...> wrote:
>
>
> Ian,
>
> I agree... not annoying enough, so, perhaps I am the one. Give me some days and I will
> commit some code to include required arguments...
>
> Thanks
> Antonio.
>
>
> --