[SR-9972] Linker error when building SwiftSyntax using SwiftPM's generated Xcodeproj in Xcode 10.2 beta 3

[hartbit]

Previous ID	SR-9972
Radar	rdar://problem/48044350
Original Reporter	@hartbit
Type	Bug
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	Project Infrastructure
Labels	Bug
Assignee	@hartbit
Priority	Medium

md5: 07ac891ad766d7dd268dcc9e0328f39e

Issue Description:

I haven't had to time to diagnose what could be causing this issue but those steps reproduce it:

1. Install Xcode 10.2 beta 3

2. Install the latest master toolchain

3. Clone the latest commit from SwiftSyntax

4. Execute:

   $ export TOOLCHAINS=swift
   $ cd swift-syntax
   $ ./build-script.py --generate-xcodeproj
   ** Generating gyb Files **
   Done Generating gyb Files
   ** Generate SwiftSyntax as an Xcode project **
   generated: ./SwiftSyntax.xcodeproj

5. Launch Xcode 10.2 beta3 with the generated project

6. Build any of the schemes.

Xcode will fail building with the following linker error:

ld: file not found: /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2019-02-19-a.xctoolchain/usr/lib/arc/libarclite_macosx.a 

On the other hand, building using either the build-script or SwiftPM directly works:

$ ./build-script.py
$ swift build 

[aciidgh]

@belkadan any idea what's going on?

[belkadan]

I think we decided that something funny was going on where we thought arclite was going to be in the toolchain but then it wasn't (maybe the arc/ directory exists but it's empty).

[hartbit]

Stupid question: why would a SwiftPM build (from the same toolchain) not generate the same error?

[belkadan]

Whether or not you need arclite depends on your deployment target. I suspect SwiftPM is always building for the host OS.

[belkadan]

Ahh, figured it out today. It's because we're now shipping Clang in the downloadable toolchain too.

[belkadan]

#22911

[belkadan]

5.1: #22923

[hartbit]

Thanks!

[hartbit]

I'm still seeing this error, even in recent toolchains. Any idea why?

[belkadan]

Hm, no. Fully the same, with your toolchain name in the path and then libarclite_macosx.a at the end?

[hartbit]

Exactly the same, yes.

[belkadan]

And which toolchain?

[hartbit]

For example, here's the error on march 26th toolchain:

ld: file not found: /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2019-03-26-a.xctoolchain/usr/lib/arc/libarclite_macosx.a 

I'll try with a more recent one.

[hartbit]

Same with the latest master toolchain:

ld: file not found: /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2019-04-10-a.xctoolchain/usr/lib/arc/libarclite_macosx.a 

[hartbit]

@belkadan I'm not the only one with the issue: #23701 (comment)