Linker produces colliding MVID for two different inputs #2203
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The new Cecil fixes the deterministic MVID and PDB checksum. Details in dotnet/cecil#31.
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#2384 brings the fix into |
The new Cecil fixes the deterministic MVID and PDB checksum. Details in dotnet/cecil#31.
Just a heads-up. We discussed an unrelated issue on Discord and found out that assemblies in different Mono runtime packs now get different MVID despite identical IL code. For reference, see these packages: Check it for System.Collections.dll, it is likely identical. Now try the same on 7.0 nightly builds and it's no longer identical. |
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The new linker behavior should be:
If anybody sees a different behavior then we need to look into that. So the question here is if the input to the linker was identical or not (note that identical IL is not enough, the above issue is that the dlls only differ in the architecture bit in the PE header, but otherwise have identical IL, those should still get different MVIDs). The new linker also fixes the PDV checksum parts - so if for some reason the difference is only in the symbols, the dlls should not be identical (and should not get the same MVIDs). |
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I agree it should be checked carefully. Some of the assemblies are originally built as AnyCPU so I would expect them to be identical if everything is deterministic (including PDB paths). Note that Xamarin.Android apparently does some deduplication by MVID so the determinism across architectures should be tested somehow. |
… in the fix for dotnet#2203 into 6.0. The same fix has been in the linker/main for 2 months now and it shipped in 7.0 preview without any issues.
Context: dotnet/runtime#45649 Context: dotnet/linker#2203 We are getting unique MVIDs per architecture output from the linker. To workaround this problem, I used the "size" of the files instead. This works for now, but is not 100% correct. I think it would be fine for .NET 7 Android apps to use this for now in main. (hopefully temporary)
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I had to make a workaround for the Android workload in our .NET 7 PR: Previously, many of the .NET assemblies output from the linker per architecture would have identical MVIDs. So for example We use this info to put architecture specific assemblies in a subfolder in the final Android app, and so you end up with only a couple duplicated assemblies. What's happening now is every assembly is different, so I changed our logic (for now) to use file size instead of MVID. That seems to workaround this for now, but should we do something else instead? |
That sounds like a very bad idea. The same file size can hide so many differences especially with alignment. |
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Yes, I definitely want to revert this. I hope before merging this PR? |
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@filipnavara Can we get those two binaries to check? We need to validate that the linker didn't regress this before we can backport to 6.0 |
Context: dotnet/runtime#56989 Context: dotnet/runtime#68734 Context: dotnet/runtime#68914 Context: dotnet/runtime#68701 Changes: dotnet/installer@04e40fa...c7afae6 % git diff --shortstat 04e40fa9...c7afae69 98 files changed, 1788 insertions(+), 1191 deletions(-) Changes: dotnet/runtime@a21b9a2...c5d40c9 % git diff --shortstat a21b9a2d...c5d40c9e 28347 files changed, 1609359 insertions(+), 1066473 deletions(-) Changes: dotnet/linker@01c4f59...04c49c9 % git diff --shortstat 01c4f590...04c49c9d 577 files changed, 28039 insertions(+), 10835 deletions(-) Updates to build with the .NET 7 SDK and use the runtime specified by the SDK. We no longer use different SDK & runtime versions. This produces a 7.0.100 Android workload. After this is merged we should be able to enable Maestro to consume future .NET 7 builds from dotnet/installer/main. ~~ Known Issues ~~ AOT+LLVM crashes on startup: * dotnet/runtime#68914 Xamarin.Build.Download hits a breaking change with `ZipEntry`: * dotnet/runtime#68734 * xamarin/XamarinComponents#1368 illink outputs different MVIDs per architecture: * dotnet/linker#2203 * dotnet/runtime#67660 Size of `libmonosgen-2.0.so` regressed: * dotnet/runtime#68330 * dotnet/runtime#68354 Newer .NET 7 builds crash on startup: * dotnet/runtime#68701 * This is worked around by *disabling* lazy loading of AOT'd assemblies 6dc426f. * TODO: re-enable once we get a fixed .NET 7 runtime. TODO: We can't yet push to the `dotnet7` feed. Working on this. Co-authored-by: Jonathan Peppers <[email protected]> Co-authored-by: Peter Collins <[email protected]>
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@jonathanpeppers What's the status here? Are we clear to backport this to 6.0? |
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dotnet/runtime#67660 is still open. I think the plan was to make a reference assembly for I don't think we can backport until this is done. We should probably do it for .NET 7/main, and if successful maybe that could be backported to .NET 6? |
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The change is already in for .NET 7, so it sounds like completing dotnet/runtime#67660 would be a ship blocker for .NET 7. I agree that we should do the work in main first, then backport. |
Fixes: dotnet#7302 Context: dotnet/linker#2203 Context: dotnet/runtime#67660 Context: dotnet#6598 This partially backports 745214d. In addition to this backport to dotnet/runtime/release/6.0: dotnet/runtime#75311 We also have another change in .NET 7 that opts into `$(TrimmerRemoveSymbols)` by default for `Release` builds. This allows the .NET 7 linker to have stable MVIDs for assemblies for each architecture. There may potentially be a dotnet/linker issue here to look into further. However, this seems to be the best fix for getting .NET 6 projects building under .NET 7 at the moment.
Fixes: #7302 Context: dotnet/linker#2203 Context: dotnet/runtime#67660 Context: #6598 This partially backports 745214d. Building a `net6.0-android` app in `Release` mode with .NET 7 can fail with many errors like: error XA4215: The Java type `androidx.activity.contextaware.OnContextAvailableListener` is generated by more than one managed type. Please change the [Register] attribute so that the same Java type is not emitted. This happens because we end up with multiple assemblies, such as: obj/Release/net6.0-android/android-arm/linked/Xamarin.AndroidX.Activity.dll obj/Release/net6.0-android/android-arm64/linked/Xamarin.AndroidX.Activity.dll obj/Release/net6.0-android/android-x64/linked/Xamarin.AndroidX.Activity.dll obj/Release/net6.0-android/android-x86/linked/Xamarin.AndroidX.Activity.dll To fix this, in addition to this backport to dotnet/runtime/release/6.0: dotnet/runtime#75311 In .NET 7 we opt into `$(TrimmerRemoveSymbols)` by default for `Release` builds. This allows the .NET 7 linker to have stable MVIDs for assemblies for each architecture. Somehow when the linker outputs `.pdb` files, it creates different MVIDs per architecture. There may potentially be a dotnet/linker issue here to look into further. However, this seems to be the best fix for getting .NET 6 projects building under .NET 7 at the moment.
…otnet/linker#2384) The new Cecil fixes the deterministic MVID and PDB checksum. Details in dotnet/cecil#31. Commit migrated from dotnet/linker@4f4a670
See dotnet/runtime#45649 for more details.
This is inherently a Cecil issue, but tracking it here since we don't normally watch Cecil repo.
Adding to 6.0.0 for now - to consider this at least.
/cc @agocke
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