Unable to compile with MSVC 19.11 (VS15.3 or VS2017.3)

[egorpugin]

Hi!

MS released VS 15.3 (2017.3) with first toolset update and build is broken in /std:c++17 mode.
Errors:

\include\sqlpp11/statement.h(156): error C2903: '_base_t': symbol is neither a class template nor a function template
\include\sqlpp11/insert.h(109): note: see reference to class template instantiation 'sqlpp::statement_t<void,sqlpp::insert_t,sqlpp::no_into_t,sqlpp::no_insert_value_list_t>' being compiled
\date.h(111): note: see reference to class template instantiation 'std::chrono::duration<int,std::ratio<86400,1>>' being compiled
\include\sqlpp11/statement.h(166): error C3546: '...': there are no parameter packs available to expand
\include\sqlpp11/statement.h(173): error C3546: '...': there are no parameter packs available to expand
\include\sqlpp11/statement.h(179): error C3546: '...': there are no parameter packs available to expand
\include\sqlpp11/table.h(48): error C2903: '_member_t': symbol is neither a class template nor a function template
\include\sqlpp11/verbatim_table.h(53): note: see reference to class template instantiation 'sqlpp::table_t<sqlpp::verbatim_table_t,sqlpp::detail::unusable_pseudo_column_t>' being compiled

sqlite3 connector 0.24 + sqlpp11 develop.

[rbock]

Hi Egor,

Are those all error messages? No static assert or anything? Can you send a minimal example that produces this or a similar error?

Thanks,

Roland

[egorpugin]

Sure. :) And yes, no other static asserts or something.

#include <sqlpp11/sqlpp11.h>

int main()
{
    return 0;
}

[rbock]

Oh, wow!

That's scary... Does it also happen if you turn off the explicit C++17 mode?

Also, can you try including sqlpp11/verbatim_table.h, only?

[egorpugin]

Oops. I've tried other modes (c++14, c++latest and no explicit) and they're broken too (with my example above).

With single sqlpp11/verbatim_table.h include:

\sqlpp11/verbatim_table.h(42): error C2039: 'make_char_sequence': is not a member of 'sqlpp'
\sqlpp11/verbatim_table.h(33): note: see declaration of 'sqlpp'
\sqlpp11/verbatim_table.h(42): error C2061: syntax error: identifier 'make_char_sequence'
\sqlpp11/verbatim_table.h(42): error C2238: unexpected token(s) preceding ';'
\sqlpp11/table.h(48): error C2903: '_member_t': symbol is neither a class template nor a function template
\sqlpp11/verbatim_table.h(53): note: see reference to class template instantiation 'sqlpp::table_t<sqlpp::verbatim_table_t,sqlpp::detail::unusable_pseudo_column_t>' being compiled
\sqlpp11/verbatim_table.h(59): error C2039: 'make_char_sequence': is not a member of 'sqlpp'
\sqlpp11/verbatim_table.h(33): note: see declaration of 'sqlpp'
\sqlpp11/verbatim_table.h(59): error C2061: syntax error: identifier 'make_char_sequence'
\sqlpp11/verbatim_table.h(59): error C2238: unexpected token(s) preceding ';'

[rbock]

Oh, ok, that is an actual error (missing include). Fixed it on develop.

Can you pull and try again?

Thanks!

[egorpugin]

With single verbatim_table.h:

\include\sqlpp11/table.h(48): error C2903: '_member_t': symbol is neither a class template nor a function template
\include\sqlpp11/verbatim_table.h(54): note: see reference to class template instantiation 'sqlpp::table_t<sqlpp::verbatim_table_t,sqlpp::detail::unusable_pseudo_column_t>' being compiled

[rbock]

Thanks! I am quite confident now that this is a compiler bug.
If you look at table.h and verbatim_table.h, you'll quickly spot the relevant parts:

  namespace detail
  {
    struct unusable_pseudo_column_t
    {
      struct _alias_t
      {
        template <typename T>
        struct _member_t // <---- This is the member template that the compiler cannot find
        {
        };
      };
      using _traits = make_traits<no_value_t>;
    };
  }

Above you see the _member_t template that the compiler cannot find here

  template <typename Table, typename... ColumnSpec>
  struct table_t : public table_base_t, public ColumnSpec::_alias_t::template _member_t<column_t<Table, ColumnSpec>>...

when specialized like this:

  struct verbatim_table_t : public table_t<verbatim_table_t, detail::unusable_pseudo_column_t>
  {
   //...
  };

I still need Microsoft's team to use sqlpp11 as a unit test :-(

It might be possible to create some alias template that wraps the ColumnSpec::_alias_t::template _member_t part. But there is a good chance that such a workaround will break older versions of MSVC.

So I do not have a good solution for this other than reporting a bug at Microsoft. Would you like to do that?

[rbock]

Does this compile on your machine?

template <typename Table, typename ColumnSpec>
struct column_t
{
};

struct table_base_t
{
};

template <typename Table, typename... ColumnSpec>
struct table_t : public table_base_t, public ColumnSpec::_alias_t::template _member_t<column_t<Table, ColumnSpec>>...
{
};

namespace detail
{
  struct unusable_pseudo_column_t
  {
    struct _alias_t
    {
      template <typename T>
      struct _member_t
      {
      };
    };
  };
}

struct verbatim_table_t : public table_t<verbatim_table_t, detail::unusable_pseudo_column_t>
{
};

int main()
{
}

That's basically the code that produced the error message (except that the struct bodies are more complex in the real code);

[egorpugin]

I'll file an issue there. I already prepared minimal not working example.

struct U { template <class T> struct b {}; };
template <typename ... Args>
struct T : Args::template b<int>... {};
struct V : public T<U> {};

[egorpugin]

https://connect.microsoft.com/VisualStudio/feedback/details/3139514

[rbock]

Awesome!

[egorpugin]

New and correct link - https://developercommunity.visualstudio.com/content/problem/95983/c-vs152-153-regression-in-variadic-template-argume.html

[egorpugin]

According to https://connect.microsoft.com/VisualStudio/feedback/details/3139514

This issue has been fixed and will be available in the next major release of VS2017.

As I understand it will be in VS15.5.

[rbock]

That's good news indeed! Thanks again for reporting it.

I also talked to members of Microsoft's compiler team at CppCon. They are looking into adding sqlpp11 to their test suite. This would help a lot.

[rbock]

Hi,

I just learned that Microsoft regularly tests their compiler against all packages in https://github.com/Microsoft/vcpkg

As am not a Windows/MSVC user, it would be awesome if somebody could take the job of adding sqlpp11.

Best,

Roland

[rbock]

As @juandent commented here rbock/sqlpp11-connector-sqlite3#36 (comment) , VS 15.5.0 Preview 5 seems to fix the problem. Keep your fingers crossed that the actual release will do so, too :-)

[rbock]

With current versions, it should be fine. Please open a new issue otherwise.