PrintAsClang is supposed to emit declarations in the same order regardless of the compiler’s internal state, but we have repeatedly found that our current criteria are inadequate, resulting in non-functionality-affecting changes to generated header content. Add a diagnostic that’s emitted when this happens soliciting a bug report.
Since there *should* be no cases where the compiler fails to order declarations, this diagnostic is never actually emitted. Instead, we test this change by enabling `-verify` on nearly all PrintAsClang tests to make sure they are unaffected.
This did demonstrate a missing criterion that only mattered in C++ mode: extensions that varied only in their generic signature were not sorted stably. Add a sort criterion for this.
Technically, these operations belong in the ObjectiveC module, where NSObject
is defined. Keep them there. However, we need to build the mock ObjectiveC
overlay with `-disable-objc-attr-requires-foundation-module` now.
SourceKit uses a clever pragma to automatically attach an attribute to
every declaration in the file. However, the form of this pragma (clang
attribute push) uses a parenthesized list marked with 'any', which turns
out to be a name that people sometimes use for macros. Guard against this
using the push_macro pragma (originally from MSVC), under the assumption
that anyone who supports the highly-use-specific 'external_source_symbol'
attribute probably implements this more common extension. This does make
the generated header a little uglier, but it's not like it was really
pretty to begin with.
rdar://problem/34168022
