[GiNaC-devel] MSVC error 2766

[Richard B. Kreckel]

Hello Jan,

On 14.02.22 20:31, Jan Rheinländer wrote:
> that was MSVC from Visual Studio 2019. But the same happens with
> 19.30.30706 from VS 2022. Also, past experience shows that MSVC is very
> strict (you might say pedantic) about the standard. So I have little
> hope that the problem will go away with a new version of MSVC.

Can you produce a stripped-down example and file a bug report against
MSVC at Microsoft, please?

> The help page for error 2766
> <https://docs.microsoft.com/en-us/cpp/error-messages/compiler-errors-2/compiler-error-c2766?view=msvc-170>
> says "Duplicate explicit specializations are not allowed". Though
> looking at the thread
> <https://www.ginac.de/pipermail/ginac-devel/2021-February/002539.html>
> you cited it would seem that the code in the header should be viewed as
> a declaration, not a definition:
> 
> />> According to 14.7.3.13 />>/"An explicit specialization of a static data member of a template is />>/a definition if the declaration includes an initializer; otherwise, />>/it's a declaration."/

I cannot add anything to the standard section you cite. According to my
reading and understanding, MSVC is confused if it thinks this is a
definition.

> On the other hand, looking at structure.h, it does assign a value to
> reg_info in the header file. So maybe the solution I suggested (move
> GINAC_IMPLEMENT_REGISTERED_CLASS_OPT_T to the header) is not that bad
> after all?

Can't we just #ifdef out the declaration for MSVC?

  -richy.