[PATCH] D86767: [libunwind] Minor SJLJ config cleanup. NFCI.

[Ryan Prichard via Phabricator via llvm-commits]

rprichard added a comment.
Herald added a subscriber: danielkiss.

In D86767#2244767 <https://reviews.llvm.org/D86767#2244767>, @steven_wu wrote:

> Sorry for the inconvenience that libunwind is not really buildable for armv7 from iOS SDK. You can build a single threaded version without referring to those interfaces. If this is really troublesome for you, feel free to file a bug report and we can see what can be done here.

Thanks. I think I'm OK as-is.

> This patch is technically not correct from a bigger context. I think, for example, watch `armv7k` doesn't default to sjlj exception model but it needs to build sjlj model to support some clients.

That makes sense. It looks like passing `-arch armv7k` to clang is enough to switch it to using DWARF and compact unwinding rather than sjlj. I also see a comment in ToolChains/Darwin.cpp:
`// Only watchOS uses the new DWARF/Compact unwinding method.`

It seems that Darwin/armv7k libunwind doesn't build because config.h enables `_LIBUNWIND_SUPPORT_COMPACT_UNWIND`, but there is no 32-bit ARM compact unwinder. It looks like setting the flag is the right thing to do, though -- maybe the rest of the code is internal to Apple.

I'll revise or abandon this patch. My main goal was to ensure that if `_LIBUNWIND_USE_DL_ITERATE_PHDR` was defined, then either of `_LIBUNWIND_ARM_EHABI` or `_LIBUNWIND_SUPPORT_DWARF_UNWIND` would also be defined.


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https://reviews.llvm.org/D86767