"inline" linkage necessary

[aaron-michaux]

The following lines in optional.hpp should have "inline" linkage. This is necessary for using <boost/optional/optional.hpp> in a module.

    const in_place_init_t in_place_init((in_place_init_t::init_tag()));

   const in_place_init_if_t
       in_place_init_if((in_place_init_if_t::init_tag()));

[aaron-michaux]

I'm not sure how this code could be correct in a header-only library without inline.

[akrzemi1]

global objects declared const have internal linkage.

[aaron-michaux]

Okay. The code breaks with `-fmodules-ts`, but that could be a bug in the standard or WIP implementation too. Aaron Michaux PhD ECE, Purdue University (765)-444-9413

…

On Wed, Nov 21, 2018 at 9:54 AM Andrzej Krzemieński < ***@***.***> wrote: global objects declared const have internal linkage. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#65 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AEYDyDEyKAbYs0icD6uImEUj2lSFs-K_ks5uxWklgaJpZM4YtPS0> .

[gast128]

Can't these be turned into inline constexpr variables with BOOST_INLINE_CONSTEXPR. I had 2 hits:

• const in_place_init_t in_place_init ((in_place_init_t::init_tag()));
• const in_place_init_if_t in_place_init_if ((in_place_init_if_t::init_tag()));

[akrzemi1]

Can't these be turned into inline constexpr variables with BOOST_INLINE_CONSTEXPR.

They could in C++17. But this has to work in C++11. I could special-case it for C++17, but there have to be sufficient motivation. Can someone point me to the place (in the IS perhaps) that tells if/why the current implementation is incompatible with modules?

[gast128]

They could in C++17. But this has to work in C++11

I think BOOST_INLINE_CONSTEXPR expands to 'inline constexpr' when available and otherwise to 'const'. It may miss the 'static const' case though. Perhaps there is a Boost guideline.