[SR-6489] SwiftPrivate fails to link on Windows

[troughton]

Previous ID	SR-6489
Radar	None
Original Reporter	@troughton
Type	Bug
Status	Resolved
Resolution	Done

Environment

Tested building for Windows x86_64.

Additional Detail from JIRA

Votes	0
Component/s	Standard Library
Labels	Bug, Swift4, Windows
Assignee	@compnerd
Priority	Medium

md5: 9e3c64f8ec53dee4e31427808c7c54b2

Issue Description:

When trying to build the standard library for Windows, SwiftPrivate must currently be disabled due to linker errors.

More specifically, the current issue is that the mangled name of TextOutputStream can't be found.

I believe @compnerd has some ideas on how to fix this; I'm filing this bug to track the completion of this task.

Example output:

Linking CXX shared library lib/swift/windows/x86_64/swiftSwiftPrivate.dll
FAILED: : && /mnt/c/swift-source/build/Ninja-ReleaseAssert/llvm-linux-x86_64/./bin/clang++ -fPIC -Wno-unknown-warning-option -Werror=unguarded-availability-new -fno-stack-protector -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -W -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wcovered-switch-default -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wstring-conversion -fcolor-diagnostics -ffunction-sections -fdata-sections -Werror=switch -Wdocumentation -Wimplicit-fallthrough -Wunreachable-code -Woverloaded-virtual -DOBJC_OLD_DISPATCH_PROTOTYPES=0 -fno-sanitize=all -DLLVM_DISABLE_ABI_BREAKING_CHECKS_ENFORCING=1 -O3 -target x86_64-unknown-windows-msvc -nostdlib -fuse-ld=lld "-L/mnt/c/swift-source/build/Ninja-ReleaseAssert/swift-linux-x86_64/./lib/swift/windows/x86_64" "-L/mnt/c/swift-source/build/Ninja-ReleaseAssert/swift-linux-x86_64/./bin/../lib/swift/windows/x86_64" "-L/mnt/c/swift-source/build/Ninja-ReleaseAssert/swift-linux-x86_64/./bin/../lib/swift/windows" "-L/mnt/c/swift-source/VCToolsInstallDir/Lib/x64" "-L/mnt/c/swift-source/Windows Kits/10/Lib/10.0.10586.0/ucrt/x64" "-L/mnt/c/swift-source/Windows Kits/10/Lib/10.0.10586.0/um/x64" "-L/mnt/c/swift-source/windows-icu/lib64/icuuc.lib" "-L/mnt/c/swift-source/windows-icu/lib64/icuin.lib" -shared -o lib/swift/windows/x86_64/swiftSwiftPrivate.dll stdlib/private/SwiftPrivate/windows/x86_64/SwiftPrivate.o -L/mnt/c/swift-source/build/Ninja-ReleaseAssert/llvm-linux-x86_64/./lib ./lib/swift/windows/x86_64/swiftCore.lib &&
/usr/bin/lld-link: error: stdlib/private/swiftprivate/windows/x86_64/swiftprivate.o: undefined symbol: _T0s16TextOutputStreamMp
clang-5.0: error: linker command failed with exit code 1

[belkadan]

Windows isn't a supported platform at this time, but we'll certainly take fixes that get it closer to working!

[compnerd]

Thanks to some help from @jckarter and @rjmccall, #14710 has a preliminary patch to help address this issue. It needs a bit more work to enhance it further, but, conceptually, should be possible to support. I think that this might be one of the last pieces missing to support doing a complete build on Windows. I think that once this is completed, asb (JIRA User) should be able to setup a Jenkins instance to run through the unit tests on a continuous basis (and eventually, pre-checkin).

[compnerd]

Adjusted the IRGen to generate a reference to the synthetic import symbol rather than trying to create the local equivalent needed for ELF/MachO.