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> -fvisibility-ms-compat @gol
1628a1630,1663
> @item -fvisibility-ms-compat
> @opindex fvisibility-ms-compat
> This flag attempts to use visibility settings to make GCC's C++
> linkage model compatible with that of Microsoft Visual Studio.
>
> The flag makes these changes to GCC's linkage model:
>
> @enumerate
> @item
> It sets the default visibility to @code{hidden}, like
> @option{-fvisibility=hidden}.
>
> @item
> Types, but not their members, are not hidden by default.
>
> @item
> The One Definition Rule is relaxed for types without explicit
> visibility specifications which are defined in more than one different
> shared object: those declarations are permitted if they would have
> been permitted when this option was not used.
> @end enumerate
>
> In new code it is better to use @option{-fvisibility=hidden} and
> export those classes which are intended to be externally visible.
> Unfortunately it is possible for code to rely, perhaps accidentally,
> on the Visual Studio behaviour.
>
> Among the consequences of these changes are that static data members
> of the same type with the same name but defined in different shared
> objects will be different, so changing one will not change the other;
> and that pointers to function members defined in different shared
> objects may not compare equal. When this flag is given, it is a
> violation of the ODR to define types with the same name differently.
>