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Diffstat (limited to 'docs/DesignDocs/VisibilityMacros.rst')
| -rw-r--r-- | docs/DesignDocs/VisibilityMacros.rst | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/docs/DesignDocs/VisibilityMacros.rst b/docs/DesignDocs/VisibilityMacros.rst index 694882dd2638..993ce2cca5fd 100644 --- a/docs/DesignDocs/VisibilityMacros.rst +++ b/docs/DesignDocs/VisibilityMacros.rst @@ -90,20 +90,21 @@ Visibility Macros The macro has an empty definition with GCC. **Windows Behavior**: `extern template` and `dllexport` are fundamentally - incompatible *on a template class* on Windows; the former suppresses + incompatible *on a class template* on Windows; the former suppresses instantiation, while the latter forces it. Specifying both on the same - declaration makes the template class be instantiated, which is not desirable + declaration makes the class template be instantiated, which is not desirable inside headers. This macro therefore expands to `dllimport` outside of libc++ but nothing inside of it (rather than expanding to `dllexport`); instead, the explicit instantiations themselves are marked as exported. Note that this - applies *only* to extern template *classes*. Extern template *functions* obey + applies *only* to extern *class* templates. Extern *function* templates obey regular import/export semantics, and applying `dllexport` directly to the - extern template declaration is the correct thing to do for them. + extern template declaration (i.e. using `_LIBCPP_FUNC_VIS`) is the correct + thing to do for them. **_LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS** Mark the member functions, typeinfo, and vtable of an explicit instantiation of a class template as being exported by the libc++ library. This attribute - must be specified on all template class explicit instantiations. + must be specified on all class template explicit instantiations. It is only necessary to mark the explicit instantiation itself (as opposed to the extern template declaration) as exported on Windows, as discussed above. |