Undefined hidden symbols when linking with `-c opt` on Linux

[jpsim]

Linker errors

ERROR: /workdir/BUILD:33:13: Linking swiftlint failed: (Exit 1): clang-13 failed: error executing command /usr/bin/clang-13 @bazel-out/k8-opt/bin/external/sourcekitten_com_github_drmohundro_SWXMLHash/SWXMLHash.autolink ... (remaining 12 arguments skipped)

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
ld.lld: error: undefined hidden symbol: __start_swift5_protocols
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __stop_swift5_protocols
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __start_swift5_protocol_conformances
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __stop_swift5_protocol_conformances
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __start_swift5_type_metadata
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __stop_swift5_type_metadata
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __start_swift5_assocty
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __stop_swift5_assocty
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __start_swift5_replace
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __stop_swift5_replace
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __start_swift5_replac2
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __stop_swift5_replac2
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __start_swift5_builtin
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())

ld.lld: error: undefined hidden symbol: __stop_swift5_builtin
>>> referenced by SwiftRT-ELF.cpp
>>>               /usr/lib/swift/linux/x86_64/swiftrt.o:(swift_image_constructor())
clang-13: error: linker command failed with exit code 1 (use -v to see invocation)

Steps to reproduce (Requires Docker):

$ git clone https://github.com/realm/SwiftLint.git
$ cd SwiftLint
$ git checkout 145175f16c6b53c2b9e7a7a9497d92d1bdcbd26a
$ docker build .

Also full logs are available on SwiftLint's CI: https://github.com/realm/SwiftLint/runs/7976793407?check_suite_focus=true

If you change -c opt for -c dbg on this line there are no linker errors: https://github.com/realm/SwiftLint/blob/145175f16c6b53c2b9e7a7a9497d92d1bdcbd26a/Dockerfile#L26

I see the same error if I build for amd64 or arm64. I don't have the same error if I build on macOS.

I'm using rules_swift 469db13

[keith]

This is because of this swift issue swiftlang/swift#60406, it only appears in opt because bazel passes --gc-sections only for opt builds. You should be able to work around it by passing --linkopt=-z --linkopt nostart-stop-gc on Linux.

[keith]

In Swift 5.7 (or maybe 5.7.1 who knows), it will be fixed by automatically adding this for you when using lld. You can also switch to a different linker to avoid this if that's easier.

[jpsim]

Thanks for linking the root issue, I'll close this since it's not rules_swift-specific.