[PATCH] D36501: Add flag to request Clang is ABI-compatible with older versions of itself

Richard Smith - zygoloid via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Fri Aug 25 11:57:58 PDT 2017

rsmith added a comment.

In https://reviews.llvm.org/D36501#852765, @probinson wrote:

> I would prefer a diagnostic if PS4 && >3.2.  Whether you map "latest" to 3.2 or diagnose that also, up to you, I'm okay either way.

On reflection, I don't think doing anything special for PS4 here is really correct. (Suppose Clang 5 has some (accidental) ABI change in it for PS4, and we fix that in Clang 6 to once again follow the psABI and do what Clang 3.2 did. In that case, building with `-fclang-abi-compat=5` should theoretically reinstate that accidental ABI change.) The old-Clang compatibility mode and the platform ABI are separate, and we should not conflate them. New patch on the way.



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