Hey all, I recently learned that my understanding of how symbol visibility works, and how one is supposed to use the export macros we all know from Qt and KDE (and that I have used for the last ~20 years) is incorrect for clang/libc++. This is mostly a PSA at this stage only, as I cannot yet accurately give a meaningful suggestion of what to do instead.
Please see https://github.com/llvm/llvm-project/issues/133725 for more details and the ongoing discussion. I'm trying to learn more, and get more documentation from the clang/libc++ folks. At the very least, the following part of Qt knowledge is _wrong_ for that specific target platform: > Never export a non-polymorphic class wholesale (From https://wiki.qt.io/Things_To_Look_Out_For_In_Reviews) Because if you do so, and the type is public (i.e. all-inline), then you would not be able to safely put that into a `std::any` in one DSO and extract it in another DSO. The worst thing is that this is only detectable at runtime. In the context of Qt, maybe not a lot of people use std::any (yet?), but being compatible with std types should be paramount I hope you all agree. So maybe a separate macro needs to be added for `[[clang::type_visibility]]` and added to all public types, until https://github.com/llvm/llvm-project/issues/133905 lands and we can use it to set this globally? Cheers -- Milian Wolff m...@milianw.de http://milianw.de
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