[SR-3033] Poor diagnostic when importing executable target module in a test

[swift-ci]

Previous ID	SR-3033
Radar	None
Original Reporter	ontouchstart (JIRA User)
Type	Bug
Status	Resolved
Resolution	Duplicate

Attachment: Download

Environment

Swift version 3.0 (swift-3.0-RELEASE)
Target: x86_64-unknown-linux-gnu
Swift Package Manager - Swift 3.0.0

Test repo:

https://github.com/thinkswift/test_main/tree/907a62c40321209f8d60e835ee58c10e999d17e4

Additional Detail from JIRA

Votes	1
Component/s	Package Manager
Labels	Bug, Linux
Assignee	None
Priority	Medium

md5: 9e3dfc420909e57213129976258c15f0

duplicates:

• SR-1503 Can't test module under linux that has main.swift in it

relates to:

• SR-1393 [SwiftPM] Enforce Swift module import dependencies

Issue Description:

swift test -v
/swift-3.0-RELEASE-ubuntu15.10/usr/bin/swiftc --driver-mode=swift -I /swift-3.0-RELEASE-ubuntu15.10/usr/lib/swift/pm -L /swift-3.0-RELEASE-ubuntu15.10/usr/lib/swift/pm -lPackageDescription /home/test_main/Package.swift -fileno 4
/swift-3.0-RELEASE-ubuntu15.10/usr/bin/swift-build-tool -f /home/test_main/.build/debug.yaml test -v
'/swift-3.0-RELEASE-ubuntu15.10/usr/bin/swiftc' -Xlinker '-rpath=$ORIGIN' -g -L/home/test_main/.build/debug -o /home/test_main/.build/debug/test_mainPackageTests.xctest -module-name test_mainPackageTests /home/test_main/Tests/LinuxMain.swift -emit-executable -I /home/test_main/.build/debug /home/test_main/.build/debug/test_mainTests.build/test_mainTests.swift.o /home/test_main/.build/debug/test_main.build/main.swift.o /home/test_main/.build/debug/test_main.build/test_no_main.swift.o
/usr/bin/ld.gold: error: /home/test_main/.build/debug/test_main.build/main.swift.o: multiple definition of 'main'
/usr/bin/ld.gold: /tmp/LinuxMain-41188c.o: previous definition here
/usr/bin/ld.gold: fatal error: /home/test_main/.build/debug/test_mainPackageTests.xctest: open: Is a directory
clang: error: linker command failed with exit code 1 (use -v to see invocation)
<unknown>:0: error: link command failed with exit code 1 (use -v to see invocation)
<unknown>:0: error: build had 1 command failures
error: exit(1): /swift-3.0-RELEASE-ubuntu15.10/usr/bin/swift-build-tool -f /home/test_main/.build/debug.yaml test -v

[ddunbar]

Is the package which reproduces this public?

[aciidgh]

It looks like you're trying to import an executable target via XCTest which is not supported
see: https://bugs.swift.org/browse/SR-1503

[swift-ci]

Comment by Sam Liu (JIRA)

@ddunbar Yes they are here:

https://github.com/thinkswift/SR-3033/releases
https://github.com/thinkswift/test_main/releases

[aciidgh]

ontouchstart (JIRA User) Both of the packages tests fine for me, the logs suggest you're linking a main.swift file with tests however that is not the case in the packages you provided. The logs also suggest that you're probably using the same build directory for linux and macOS. Make sure you delete the build dir (rm -r .build) if you're mounting and building on Linux

[swift-ci]

Comment by Sam Liu (JIRA)

@aciidb0mb3r I think you are right, it is duplicated by SR-1503

Per @ddunbar's suggestion via twitter, I made some change in version 0.0.1 and it works. I wonder if this is a short term hack before it if fixed in Linux or a recommended best practice for the future packages with cli.

https://gist.github.com/ontouchstart/37d70553c95c626db7c3ddf47bcf6156

https://gist.github.com/ontouchstart/06a272456d7a56cfff8bba012625c40e

Thanks for the hard work.

[swift-ci]

Comment by Sam Liu (JIRA)

@aciidb0mb3r I wrapped test_main package with an empty SR-3033 for easy version control. both test_main-0.0.0 and test_main-0.0.1 work in macOS for sure. For Linux. My gists above test them in fresh docker containers without any macOS build. You should be able to reproduce them. I put Makefile back in the gists:

https://gist.github.com/ed8b21af4ad67b3e9352c0a0018222d8
https://gist.github.com/1bbd27027278a72e36e51f00cfadfb12

[swift-ci]

Comment by Sam Liu (JIRA)

I noticed that in my 0.0.0 test, there is a mismatch of file name and module name. I renamed it in version 0.0.3

https://github.com/thinkswift/test_main/releases/tag/0.0.3

The result is the same:

https://gist.github.com/1f0290e8f853968c80e68e53bb9e6efe

[aciidgh]

FWIW, you wouldn't get these errors now since we don't link executables anymore and consider them only as build order dependencies

[swift-ci]

Comment by Sam Liu (JIRA)

What do you mean "now"? Here is a test in swift-DEVELOPMENT-SNAPSHOT-2016-10-21-a-ubuntu16.04

https://gist.github.com/1d280dd66838f808e692482ba6f0c089

[swift-ci]

Comment by Sam Liu (JIRA)

SR-3033 combined test for 0.0.3 swift-DEVELOPMENT-SNAPSHOT-2016-10-21-a-ubuntu16.04 and macox

https://gist.github.com/a3c15044517e314f1cfef2b99cf2cd97

[aciidgh]

/SR-3033/Packages/test_main-0.0.3/Tests/test_mainTests/test_mainTests.swift:8: error: undefined reference to 'TFV9test_main9test_mainCfT_S0'

Yup, This is expected now since you can't "import" executable modules however it is guaranteed to be built before your test module (i.e. executables are build order dependencies) so you can popen and test your executables functionally (we do this in SwiftPM).
The error here should have been at the import statement but since we include the build folder in import paths (where that and all the other compiled modules are present) it lets you compile the test module with that import statement but fails at linking since we don;t link that module's object file(s).

TL;DR We need to have a better error message if someone tries to import executables but I don't know if its possible to do that at this stage.

[swift-ci]

Comment by Sam Liu (JIRA)

Tests on test_main package directly instead of as a sub package.

https://gist.github.com/9b9b4d60673ceb2f92f239d236160ec3 (0.0.3 failed)
https://gist.github.com/e59b97b2b474d16f0344ba476f64d609 (0.0.1 works)

[ddunbar]

Ah, I see now. This probably requires SR-1393 (linked).

[swift-ci]

Comment by Sam Liu (JIRA)

@ddunbar @aciidb0mb3r Do you think this test might be related ?

https://gist.github.com/103babaa6710c4b92be613237622d1d3
https://gist.github.com/03076e1df51c30ce592dddee9c0bdcc0

[swift-ci]

Comment by Sam Liu (JIRA)

More test in https://gist.github.com/846d355429e7676e87197ee3928bb7a9

A few observations:

1. test_main-0.0.4 (https://github.com/thinkswift/test_main/tree/0.0.4) has no exported public interface but an executable .build/debug/test_main . Although useless as a module, it is an example of package as a utility.

2. SR-3033-0.0.4 (https://github.com/thinkswift/SR-3033/blob/0.0.4/Package.swift) includes test_main-0.0.4 as the dependency only for the utility purpose

3. The first run of swift build failed to build on both Linux and macOS

https://gist.github.com/ontouchstart/846d355429e7676e87197ee3928bb7a9#file-linux_stdout-log-L41 (Linux)
https://gist.github.com/ontouchstart/846d355429e7676e87197ee3928bb7a9#file-mac_stdout-log-L40 (macOS)

4. Second run of swift build was successful. Although the test_main module has not public interface to be used in SR-3033, there is no compiler/linker error either. The binary .build/debug/test_main works

https://gist.github.com/ontouchstart/846d355429e7676e87197ee3928bb7a9#file-linux_stdout-log-L196 (Linux)
https://gist.github.com/ontouchstart/846d355429e7676e87197ee3928bb7a9#file-mac_stdout-log-L194 (macOS)

and test works on both Linux and macOS.

I am not raising this issue from technical but user experience standpoint . In integrated interactive development environment like xcode, packages are mostly used as library provider, not utilities. In non-integrated development environment like Linux/UNIX, standalone utilities become powerful and flexible tools in the development toolchain. Reliable support of swift package as utility might be very helpful for backend developers down the road.