Re: Wrong class export/visibility setting for shared libs in many Boost libs

From: Peter Dimov (pdimov_at_[hidden])
Date: 2021-02-02 14:09:55

Andrey Semashev wrote:
> So, the bottom line, BOOST_PROGRAM_OPTIONS_DECL must be defined to:
>
> - BOOST_SYMBOL_EXPORT - on Windows, when the library is being built;
> - BOOST_SYMBOL_IMPORT - on Windows, when the library is being consumed by 
> user;
> - BOOST_SYMBOL_VISIBLE - in any other case.

BOOST_SYMBOL_EXPORT is defined to BOOST_SYMBOL_VISIBLE on non-Windows in 
order to make the third case unnecessary. Alexander suggests that on macOS 
(but not Linux), it's also necessary to define BOOST_SYMBOL_IMPORT to 
BOOST_SYMBOL_VISIBLE (instead of to nothing) on non-Windows. This seems 
sensible.

In other words,

- BOOST_SYMBOL_EXPORT - when the library is being built;
- BOOST_SYMBOL_IMPORT - when the library is being consumed by user.