Linux Support

[rhyshort]

With the merging of URLSession into swift corelibs, (See swiftlang/swift-corelibs-foundation#426) it should be possible to compile on Linux.

Once a snapshot is published we should take the opportunity to see if we compile on linux and fix and issues that arise.

[rolivieri]

@rhyshort Hello, it is our understanding that with the latest development snapshot (8/25), libdispatch, NSURLSession and friends are now available: https://swift.org/download/#snapshots.

[rhyshort]

Yes they are available, there a few niggles to get through, so far I've got library compiling on Linux, just need to fix up the tests.

[rolivieri]

That's great! Looking forward to using the Cloudant SDK on linux.

[rhyshort]

Being able to test on Linux is currently blocked by SR-2170.

[rhyshort]

Bad news on this. With the release of Swift 3, there are still issues that we can't overcome. The biggest being unable to link due to SR-2170. Which has yet to be fixed (error attached below). I think we will need to wait for a few patch releases before we can add linux support as it currently stands.

Error:

Linking ./.build/debug/SwiftCloudantPackageTests.xctest
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationg6_queueXwGSqCS_14OperationQueue_' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operations6_queueXwGSqCS_14OperationQueue_' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationm6_queueXwGSqCS_14OperationQueue_' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationg10_cancelledSb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operations10_cancelledSb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationm10_cancelledSb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationg10_executingSb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operations10_executingSb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationm10_executingSb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationg9_finishedSb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operations9_finishedSb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationm9_finishedSb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationg6_readySb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operations6_readySb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationm6_readySb' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationg13_dependenciesGVs3SetS0__' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operations13_dependenciesGVs3SetS0__' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationm13_dependenciesGVs3SetS0__' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationg6_groupC8Dispatch13DispatchGroup' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operations6_groupC8Dispatch13DispatchGroup' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationm6_groupC8Dispatch13DispatchGroup' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationg9_depGroupC8Dispatch13DispatchGroup' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operations9_depGroupC8Dispatch13DispatchGroup' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationm9_depGroupC8Dispatch13DispatchGroup' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationg7_groupsGSaC8Dispatch13DispatchGroup_' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operations7_groupsGSaC8Dispatch13DispatchGroup_' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operationm7_groupsGSaC8Dispatch13DispatchGroup_' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operation12_leaveGroupsfT_T_' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operation6finishfT_T_' is not defined locally
/usr/bin/ld.gold: error: hidden symbol '_TFC10Foundation9Operation15_waitUntilReadyfT_T_' is not defined locally
clang: error: linker command failed with exit code 1 (use -v to see invocation)

[rhyshort]

The related SR-1901 has been fixed. Not sure if it would fix the issue throughout foundation without verification however.

There are also a couple of issues with Foundation on linux JSONSeralisation, booleans are stored as NSNumber on linux and can't be cast to Bool like it can be on Apple platforms. HTTPCookieStorage is also lacking the shared storage option, we use it so we can access cookies later, and have our tests interact with the same cookie storage object.

[rhyshort]

Small update, all of HTTPCookieStorage is currently unimplemented see https://github.com/apple/swift-corelibs-foundation/blob/7400a09/Foundation/NSHTTPCookieStorage.swift

[pushkarnk]

Yes, we'll start looking at HTTPCookieStorage.

[rhyshort]

HTTPCookieStorage PR swiftlang/swift-corelibs-foundation#672 its been open quite a while and doesn't look like its going to get merged anytime soon.

[rhyshort]

With swiftlang/swift-corelibs-foundation#836 merged, one less barrier to running on linux.

[benspratling4]

Is this fixed in Swift 3.1?

[rhyshort]

No not yet, cookie support hasn't been merged so that is still a blocker.

[rhyshort]

The linux testing will need to be expanded from just 14.04, to cover:

• 14.04
• 16.04
• 16.10

should be straight forward to add to the matrix.

[ianpartridge]

I've just merged the linux-support branch to master. With this, the Cloudant testsuite passes on Linux when run against the latest Swift 4 snapshot from swift.org.

Once Swift 4 is released we'll be able to declare Linux support!

[ricellis]

Thanks @ianpartridge
We'll have to figure out whether this library becomes Swift 4 only or how easy it is to support both 4 and 3 (for non-linux).

[ianpartridge]

As of today it compiles on both Swift 3 and 4, so hopefully we can support both.

[gmosx]

Now that Swift 4 is released, what's the status of this issue?

[rhyshort]

There are currently test failures that need investigating: https://travis-ci.org/cloudant/swift-cloudant/jobs/277632910

[ianpartridge]

Hmm, that's annoying, it must be a regression somewhere.

[gmosx]

So, any updates?

[ricellis]

I'm closing this ticket, the Linux support work in this library has been done for quite a while (although not released). There is a remaining issue with the GetChangesOperation which I think should be tracked separately see #176.