[swift-dev] Proof-of-concept port of Swift for Android

[Geordie Jay]

Hi Joe,

I was just commenting on your @_cdecl commit on GitHub but I’ll keep the discussion here.




I was wondering what it is about your implementation that makes it rely on ObjC interop, as you noted. And whether this dependency can be removed for a quick and dirty proof of concept, or whether it’s something more fundamental than that?







In this (admittedly very simple) example, the author just calls the mangled name from C and appears to get away with it:

http://romain.goyet.com/articles/running_swift_code_on_android/




Makes me wonder whether the @_silgen_name approach wouldn’t suffice after all for a proof of concept?




Best regards,

Geordie




(Joe: apologies for the double up, I’m evidently terrible at mailing lists and hit reply instead of reply all!)

On Fri, Dec 11, 2015 at 5:53 PM, Joe Groff <jgroff at apple.com> wrote:

>> On Dec 11, 2015, at 7:13 AM, Douglas Gregor via swift-dev <swift-dev at swift.org> wrote:
>> 
>> 
>>> On Dec 11, 2015, at 4:33 AM, Geordie Jay via swift-dev <swift-dev at swift.org> wrote:
>>> 
>>> Hi, maybe one of the Apple devs can help out with this quick Q:
>>> 
>>> To interface with the JNI, we’d presumably need to call swift functions from our compiled swift binaries from C (or directly from Java, the result being the same). Is there a way to demangle certain symbols in the output binary to this effect, or is there another / a better way to access Swift functions from C?
>> 
>> Others can probably give a more detailed response, but...
>> 
>> There’s a Swift demangler in Swift’s “Basic” library (lib/Basic/Demangle.cpp), along with a standalone tool (swift-demangle) you can experiment with. The information in the mangled name should be complete enough to call, but you’ll need to match Swift’s calling convention.
>> 
>> If it’s just a specific set of Swift functions you want to call from C, you can use the @_silgen_name attribute to override the mangled name, and/or make them @convention(c) to use the C calling convention.
> @_silgen_name isn't the right answer here, since the convention will be wrong, and it won't interact properly with Clang imports and exports. Like Slava said, you want something like the '@_cdecl' attribute he proposed and I half-implemented.
> -Joe
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