[clang] Make __declspec(novtable) available in GNU driver mode

[void2012]

My low-level library makes heavy use of __declspec(novtable) attribute in the MSVC mode and it significantly reduces the size of binaries by removing the unneeded vftables. This attribute also allows the compiler to not to insert vftable assignments on constructors and destructors, as they are reassigned anyway in my library. Clang already implements __declspec(novtable) in MSVC driver mode and it would be great to have this attribute available in both GNU and MSVC modes, for example as in form of the C++11-compatible attribute syntax [[clang::novtable]].

Thanks!

[llvmbot]

@llvm/issue-subscribers-clang-driver

Author: void_17 (void2012)

My low-level library makes heavy use of `__declspec(novtable)` attribute in the MSVC mode and it significantly reduces the size of binaries by removing the unneeded vftables. This attribute also allows the compiler to not to insert vftable assignments on constructors and destructors, as they are reassigned anyway in my library. Clang already implements `__declspec(novtable)` in MSVC driver mode and it would be great to have this attribute available in both GNU and MSVC modes, for example as in form of the C++11-compatible attribute syntax `[[clang::novtable]]`.

Thanks!

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: void_17 (void2012)

My low-level library makes heavy use of `__declspec(novtable)` attribute in the MSVC mode and it significantly reduces the size of binaries by removing the unneeded vftables. This attribute also allows the compiler to not to insert vftable assignments on constructors and destructors, as they are reassigned anyway in my library. Clang already implements `__declspec(novtable)` in MSVC driver mode and it would be great to have this attribute available in both GNU and MSVC modes, for example as in form of the C++11-compatible attribute syntax `[[clang::novtable]]`.

Thanks!