[release/7.0] Disable objc_msgSend stubs in clang for compatibility with Xcode 13 #91117
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…ith Xcode 13 Backport of dotnet#89932 and dotnet#90217 to release/7.0
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Tagging subscribers to 'os-ios': @steveisok, @akoeplinger, @kotlarmilos Issue DetailsBackport of #89932 and #90217 to release/7.0 Customer ImpactAs soon as we're updating the macOS build machine image used to build dotnet/runtime to one that uses Xcode 14 the native build of Objective-C code will start emitting objc_msgSend stubs. This causes the native libraries to fail during linking with the linker in Xcode 13, effectively preventing Mac/iOS/tvOS apps from working. Note that this can happen automatically if AzDO updates the macOS build images. The fix is to disable the objc_msgSend stubs via a compiler flag, following what xamarin-macios did a while ago: xamarin/xamarin-macios#16231 TestingCI and local testing RiskLow. The PR adds an additional compiler flag to every .m Objective-C file to prevent the new Xcode 14 behavior.
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| if(CLR_CMAKE_HOST_OSX OR CLR_CMAKE_HOST_MACCATALYST OR CLR_CMAKE_HOST_IOS OR CLR_CMAKE_HOST_TVOS) | ||
| # Clang will by default emit objc_msgSend stubs in Xcode 14, which ld from earlier Xcodes doesn't understand. | ||
| # We disable this by passing -fno-objc-msgsend-selector-stubs to clang. | ||
| # We can probably remove this flag once we require developers to use Xcode 14. |
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For my knowledge - Do we have any documentation highlighting minimum supported Xcode versions?
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I found https://learn.microsoft.com/en-us/xamarin/cross-platform/get-started/requirements#macos-requirements but that seems to be a bit outdated and doesn't really mention the Xcode version directly.
The code seems to check for Xcode 6.0 but that is probably way older than is reasonable:
https://github.com/rolfbjarne/xamarin-macios/blob/577af1046738e919e15962b917e065f5589366ef/tools/mtouch/mtouch.cs#L123
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Backport of #89932 and #90217 to release/7.0
Customer Impact
As soon as we're updating the macOS build machine image used to build dotnet/runtime to one that uses Xcode 14 the native build of Objective-C code will start emitting objc_msgSend stubs. This causes the native libraries to fail during linking with the linker in Xcode 13, effectively preventing Mac/iOS/tvOS apps from working. Note that this can happen automatically if AzDO updates the macOS build images.
The fix is to disable the objc_msgSend stubs via a compiler flag, following what xamarin-macios did a while ago: xamarin/xamarin-macios#16231
Testing
CI and local testing
Risk
Low. The PR adds an additional compiler flag to every .m Objective-C file to prevent the new Xcode 14 behavior.