Cleanup uses of SWIFT_RT_ENTRY_VISBILITY

[hughbe]

And clang-format the effected method signatures - previously there was extern "C", so signatures flow differently

[swiftix]

@hughbe How you decide when you can remove those SWIFT_RT_ENTRY_VISBILITY specifiers?

[hughbe]

Sorry, I was about to fill in some info. Basically, in #6820 there was a discussion with @gparker42

Summary is, I identified all cases where SWIFT_RT_ENTRY_VISBILITY was used unecessarily, according to this comment from Greg:

SWIFT_RUNTIME_EXPORT has both extern "C" and __declspec as appropriate
every export has a header declaration
header declarations of exports all use SWIFT_RUNTIME_EXPORT
non-header definitions do not use SWIFT_RUNTIME_EXPORT or extern "C" or __declspec.

[hughbe]

@swift-ci please smoke test

[swiftix]

@hughbe I'm not 100% about this. It was me who added those SWIFT_RT_ENTRY_VISBILITY when I was working on the new calling convention for the Swift runtime functions. The idea of using a macro was useful, because it allows you to easily flip the visibility of a function based on the configuration in Config.h.

If you remove these specifiers now, how one can easily change the visibility of symbols without touching a lot of places in the source code?

[hughbe]

Also, quick Q for @gparker42 or anyone else with the knowledge

Functions defined in RuntimeFunctions.def: https://github.com/apple/swift/blob/adc54c8a4d13fbebfeb68244bac401ef2528d6d0/include/swift/Runtime/RuntimeFunctions.def

are declared extern "C" in the header without any visibility or declspec attributes. However, they are implemented in terms of extern C declspec(dllexport).

E.g.
// bool swift_isClassType(type*);

Definition: https://github.com/apple/swift/blob/adc54c8a4d13fbebfeb68244bac401ef2528d6d0/include/swift/Runtime/RuntimeFunctions.def#L1003
Implementation: https://github.com/apple/swift/blob/master/stdlib/public/runtime/Casting.cpp#L3234

What should we do in these cases?
Maybe we change the definition here: https://github.com/apple/swift/blob/ac57b66c99f9e5f8dd023245a28447613f74d08d/stdlib/public/runtime/RuntimeEntrySymbols.cpp#L49

[hughbe]

If you remove these specifiers now, how one can easily change the visibility of symbols without touching a lot of places in the source code?

The whole point is that this reduces the number of places we actually need to change the visibility of symbols. Basically, the issue right now is that we define a method as SWIFT_RT_ENTRY_VISIBILITY in the header. Then, in the implementation, we repeat SWIFT_RT_ENTRY_VISIBILITY.

This is unnecessary and we don't need to duplicate the visbiility in the cpp file as well as the .h file

[swiftix]

Oh, I missed the point that the symbols have the same specifier in the header. Sorry. No objections then.

[hughbe]

Messed up on OSX (objc specific method)

[hughbe]

@swift-ci please smoke test

[hughbe]

@gparker42 @swiftix good to merge?

[swiftix]

@hugbe LGTM