[clang] [Clang] Add __datasizeof (PR #67805)

[Aaron Ballman via cfe-commits]

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@@ -1016,4 +1016,7 @@ def warn_unpacked_field
 def warn_unaligned_access : Warning<
   "field %1 within %0 is less aligned than %2 and is usually due to %0 being "
   "packed, which can lead to unaligned accesses">, InGroup<UnalignedAccess>, DefaultIgnore;
+
+def err_cannot_mangle_expression : Error<
+  "cannot yet mangle %0 expression">;
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AaronBallman wrote:

Ah, so the "obvious" may be more obvious to people used to working with Clang's diagnostics and not so obvious to folks not as well-versed. Good feedback!

I'm okay with the changes but I have a preference for doing this in two steps. Step 1: your patch w/custom diagnostics engine, Step 2: replace all custom diagnostics with the regular diagnostic in one go. (This makes code archeology easier because the changes are kind of orthogonal to one another.) Would you be okay with splitting it up despite the extra work?

https://github.com/llvm/llvm-project/pull/67805