[PATCH] D85802: [clang] Add -fc++-abi= flag for specifying which C++ ABI to use

[Reid Kleckner via Phabricator via cfe-commits]

rnk added a comment.

In D85802#2331403 <https://reviews.llvm.org/D85802#2331403>, @leonardchan wrote:

> Perhaps we can add some mechanism in Clang that determines which ABIs are supported for specific platforms? That is, when targetting Linux, Clang will diagnose an error if using `-fc++-abi=microsoft`. This could cover the case where a specific platform can support multiple ABIs, but those ABIs won't be supported by other platforms.

Right, but the simplest code is the code that doesn't exist: if the option doesn't exist, there's no need to diagnose anything. The rest of the "C++ ABIs" aren't really their own C++ ABIs, they are just a reflection of the target triple.

What is the actual use case? I read the RFC, but ever since I became a manager, my reading comprehension level dropped back to grade school, and I apologize for that. As I understood it, you need a flag that enables all the Itanium ABI extensions (relative vtables, and others) used in Fuchsia, at once. A single relative vtable ABI flag isn't sufficient (would it be?).


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https://reviews.llvm.org/D85802