| Issue |
56068
|
| Summary |
MSVC incompatibility for dllimport/dllexport and function-local classes
|
| Labels |
clang:frontend,
platform:windows
|
| Assignees |
|
| Reporter |
pogo59
|
MSVC appears to have decided that dllimport/dllexport force external linkage, while Clang decided they are incompatible with external linkage. MSVC also documents that a dllimport/dllexport derived class with a templated base class causes the base class instantiation to inherit the dllimport/dllexport attribute.
(I don't see a way to add an attachment so the exhausting test case pasted inline.)
```
#define IMPORT __declspec(dllimport)
#define EXPORT __declspec(dllexport)
class Base {};
class IMPORT ImportedBase {};
class EXPORT ExportedBase {};
template<class T> class TmplBase {};
template<class T> class IMPORT ImportedTmplBase {};
template<class T> class EXPORT ExportedTmplBase {};
void dummy() {
// Both compilers are happy with these.
class LocalBase : public Base {};
class LocalImportedBase : public ImportedBase {};
class LocalExportedBase : public ExportedBase {};
class LocalTmplBase : public TmplBase<int> {};
class LocalImportedTmplBase : public ImportedTmplBase<int> {};
class LocalExportedTmplBase : public ExportedTmplBase<int> {};
class LocalCRTP : public TmplBase<LocalCRTP> {};
// Clang complains about all of the rest.
class IMPORT ImportedLocalBase : public Base {};
class IMPORT ImportedLocalImportedBase : public ImportedBase {};
class IMPORT ImportedLocalExportedBase : public ExportedBase {};
class IMPORT ImportedLocalTmplBase : public TmplBase<int> {};
class IMPORT ImportedLocalImportedTmplBase : public ImportedTmplBase<int> {};
class IMPORT ImportedLocalExportedTmplBase : public ExportedTmplBase<int> {};
class EXPORT ExportedLocalBase : public Base {};
class EXPORT ExportedLocalImportedBase : public ImportedBase {};
class EXPORT ExportedLocalExportedBase : public ExportedBase {};
class EXPORT ExportedLocalTmplBase : public TmplBase<int> {};
class EXPORT ExportedLocalImportedTmplBase : public ImportedTmplBase<int> {};
class EXPORT ExportedLocalExportedTmplBase : public ExportedTmplBase<int> {};
class IMPORT ImportLocalCRTP : public TmplBase<ImportLocalCRTP> {};
class EXPORT ExportLocalCRTP : public TmplBase<ExportLocalCRTP> {};
// CRTP where template is dllimport/dllexport gets an extra Note.
class IMPORT ImportImportLocalCRTP : public ImportedTmplBase<ImportImportLocalCRTP> {};
class IMPORT ImportExportLocalCRTP : public ExportedTmplBase<ImportExportLocalCRTP> {};
class EXPORT ExportImportLocalCRTP : public ImportedTmplBase<ExportImportLocalCRTP> {};
class EXPORT ExportExportLocalCRTP : public ExportedTmplBase<ExportExportLocalCRTP> {};
}
```
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