[PATCH] D101972: Do not set CMAKE_CXX_VISIBILITY_PRESET to hidden

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a subscriber: zturner.
rnk added a comment.

> As an example, llvm::Any::TypeId::Id relies on the uniqueness of the address of a
> static variable defined in a template function.

I just read that line, and I'm thinking to myself, obviously that won't work, don't do that, it doesn't work with DLLs, it doesn't work with hidden visibility. I *just* helped prepare a talk explaining that this code pattern isn't portable. Ideally, I would like to move in the direction of compiling *more* of LLVM with hidden visibility, not less. LLVM shared libraries already have far too many dynamic symbols. I believe Lang Hames attempted to use this code pattern in the past to refactor the pass ID into a template base class, and we reverted it for the same reasons. I wasn't able to quickly find the patch for reference.

What code actually uses llvm::Any? I only see 8 includes of Any.h across the codebase. It looks like @zturner added it in 2018 for use in unit tests. Could we remove it? If we do need it, surely the standard C++17 implementation of std::any supports compiling with fvisibility=hidden, so could we just use whatever solution the STL uses? Maybe just put default visibility on the typeid global?


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  https://reviews.llvm.org/D101972/new/

https://reviews.llvm.org/D101972