Roll clang and buildroot

[zanderso]

Rolls the buildroot to pick up a compensating change for new warnings: flutter/buildroot@8a1cf15, flutter/buildroot@9f99fc0

And combines the three rolls:
#33278
#33279
#33280

[zanderso]

It looks like -fembed-bitcode-marker is leading to some issues with the new toolchain in the ios_debug build, from https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8814350562663012177/+/u/build_ios_debug/stdout?format=raw

ld64.lld: warning: Option `-bitcode_process_mode' is undocumented. Should lld implement it?
ld64.lld: error: cannot open marker: No such file or directory
clang-15: error: linker command failed with exit code 1 (use -v to see invocation)

The link is successful when I remove the -fembed-bitcode-marker flag. @dnfield @jmagman is that flag necessary, or is it an optimization?

[dnfield]

It's expected to be used for debug builds - it basically says to add a section that syas "here's where the bitcode would go".

This seems like a regression in clang to me...

[dnfield]

https://reviews.llvm.org/D29066 - forwarding this argument has been around for a while

[ilovepi]

I don't think lld supports the -bitcode_process_mode flag yet. There is even a fixme for it in Clang's Darwin driver. You may have to fall back to ld64 on OSX until that is implemented if you require this feature.

https://github.com/llvm/llvm-project/blob/c2fb9c29b4076da8f68a27df2bee4a2f3c81c830/clang/lib/Driver/ToolChains/Darwin.cpp#L369

[jmagman]

The link is successful when I remove the -fembed-bitcode-marker flag. @dnfield @jmagman is that flag necessary, or is it an optimization?

It's necessary, without it projects with bitcode on (like most add-to-app projects) will get an error when they link on frameworks without the marker, even in debug mode.

Tested linking a bitcode app on a framework with and without -fembed-bitcode-marker. Without:

Ld /Users/m/Library/Developer/Xcode/DerivedData/TestMarker-dyotdkaassckftfqxmijpypbotqh/Build/Products/Debug-iphoneos/TestMarker.app/TestMarker normal (in target 'TestMarker' from project 'TestMarker')
    cd /Users/m/Projects/TestMarker
    /Users/m/Applications/Xcode-13-3-1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -target arm64-apple-ios15.4 -isysroot /Users/m/Applications/Xcode-13-3-1.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS15.4.sdk -L/Users/m/Library/Developer/Xcode/DerivedData/TestMarker-dyotdkaassckftfqxmijpypbotqh/Build/Products/Debug-iphoneos -F/Users/m/Library/Developer/Xcode/DerivedData/TestMarker-dyotdkaassckftfqxmijpypbotqh/Build/Products/Debug-iphoneos -filelist /Users/m/Library/Developer/Xcode/DerivedData/TestMarker-dyotdkaassckftfqxmijpypbotqh/Build/Intermediates.noindex/TestMarker.build/Debug-iphoneos/TestMarker.build/Objects-normal/arm64/TestMarker.LinkFileList -Xlinker -rpath -Xlinker @executable_path/Frameworks -dead_strip -Xlinker -object_path_lto -Xlinker /Users/m/Library/Developer/Xcode/DerivedData/TestMarker-dyotdkaassckftfqxmijpypbotqh/Build/Intermediates.noindex/TestMarker.build/Debug-iphoneos/TestMarker.build/Objects-normal/arm64/TestMarker_lto.o -Xlinker -export_dynamic -Xlinker -no_deduplicate -fembed-bitcode-marker -fobjc-arc -fobjc-link-runtime -framework TestFW -Xlinker -no_adhoc_codesign -Xlinker -dependency_info -Xlinker /Users/m/Library/Developer/Xcode/DerivedData/TestMarker-dyotdkaassckftfqxmijpypbotqh/Build/Intermediates.noindex/TestMarker.build/Debug-iphoneos/TestMarker.build/Objects-normal/arm64/TestMarker_dependency_info.dat -o /Users/m/Library/Developer/Xcode/DerivedData/TestMarker-dyotdkaassckftfqxmijpypbotqh/Build/Products/Debug-iphoneos/TestMarker.app/TestMarker

ld: '/Users/m/Library/Developer/Xcode/DerivedData/TestMarker-dyotdkaassckftfqxmijpypbotqh/Build/Products/Debug-iphoneos/TestFW.framework/TestFW' does not contain bitcode. You must rebuild it with bitcode enabled (Xcode setting ENABLE_BITCODE), obtain an updated library from the vendor, or disable bitcode for this target. file '/Users/m/Library/Developer/Xcode/DerivedData/TestMarker-dyotdkaassckftfqxmijpypbotqh/Build/Products/Debug-iphoneos/TestFW.framework/TestFW' for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Shouldn't build ios_debug be using clang from Xcode's toolchain? What version is being rolled in? Always keeping an eye out for http://requiem/doc/postmortem126775.

[dnfield]

ios_debug isn't using Xcode because it's not actually embedding any bitcode, and that way we can use GOMA.

[dnfield]

The idea is if you're only using bitcode-marker there aren't compatibility concerns between toolchains

[dnfield]

Falling back to ld64 should be fine - that would still let us use GOMA.

[jmagman]

The idea is if you're only using bitcode-marker there aren't compatibility concerns between toolchains

That makes sense, was just checking it wasn't being used in release.

[dnfield]

Woohoo we're green