MetadataReader does not work on ARM

[wfurt]

I was trying to build corefx on Linux arm:

  Unhandled Exception: System.DataMisalignedException: A datatype misalignment was detected in a load or store instruction.
     at Microsoft.Cci.MetadataReader.PEFileToObjectModel.GetDefaultValue(MetadataObject metadataObject)
     at Microsoft.Cci.MetadataReader.ObjectModelImplementation.FieldDefinition.get_CompileTimeValue()
     at Microsoft.Cci.MutableCodeModel.FieldDefinition.Copy(IFieldDefinition fieldDefinition, IInternFactory internFactory)
     at Microsoft.Cci.MutableCodeModel.MetadataShallowCopier.CopyUnspecialized(IFieldDefinition fieldDefinition)
     at Microsoft.Cci.MutableCodeModel.MetadataShallowCopier.MetadataDispatcher.Visit(IFieldDefinition fieldDefinition)
     at Microsoft.Cci.MetadataReader.ObjectModelImplementation.FieldDefinition.Dispatch(IMetadataVisitor visitor)
     at Microsoft.Cci.MutableCodeModel.MetadataShallowCopier.Copy(IFieldDefinition fieldDefinition)
     at Microsoft.Cci.MutableCodeModel.MetadataDeepCopier.Populator.Visit(IFieldDefinition fieldDefinition)
     at Microsoft.Cci.MetadataReader.ObjectModelImplementation.FieldDefinition.Dispatch(IMetadataVisitor visitor)
     at Microsoft.Cci.MetadataTraverser.Traverse(IFieldDefinition fieldDefinition)
     at Microsoft.Cci.MetadataTraverser.Traverse(IEnumerable`1 fields)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(ITypeDefinition typeDefinition)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(INamedTypeDefinition namedTypeDefinition)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(INamespaceTypeDefinition namespaceTypeDefinition)
     at Microsoft.Cci.MetadataTraverser.Traverse(INamespaceTypeDefinition namespaceTypeDefinition)
     at Microsoft.Cci.MetadataTraverser.Dispatcher.Visit(INamespaceTypeDefinition namespaceTypeDefinition)
     at Microsoft.Cci.MetadataReader.ObjectModelImplementation.NamespaceType.Dispatch(IMetadataVisitor visitor)
     at Microsoft.Cci.MetadataTraverser.Traverse(IEnumerable`1 namespaceMembers)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(INamespaceDefinition namespaceDefinition)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(IUnitNamespace namespaceDefinition)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(INestedUnitNamespace nestedUnitNamespace)
     at Microsoft.Cci.MetadataTraverser.Traverse(INestedUnitNamespace nestedUnitNamespace)
     at Microsoft.Cci.MetadataTraverser.Dispatcher.Visit(INestedUnitNamespace nestedUnitNamespace)
     at Microsoft.Cci.MetadataReader.ObjectModelImplementation.NestedNamespace.Dispatch(IMetadataVisitor visitor)
     at Microsoft.Cci.MetadataTraverser.Traverse(IEnumerable`1 namespaceMembers)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(INamespaceDefinition namespaceDefinition)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(IUnitNamespace namespaceDefinition)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(IRootUnitNamespace rootUnitNamespace)
     at Microsoft.Cci.MetadataTraverser.Traverse(IRootUnitNamespace rootUnitNamespace)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(IModule module)
     at Microsoft.Cci.MetadataTraverser.TraverseChildren(IAssembly assembly)
     at Microsoft.Cci.MetadataTraverser.Traverse(IAssembly assembly)
     at Microsoft.Cci.MutableCodeModel.MetadataDeepCopier.Copy(IAssembly assembly)
     at GenFacades.Generator.Execute(String seeds, String contracts, String facadePath, Version assemblyFileVersion, Boolean clearBuildAndRevision, Boolean ignoreMissingTypes, Boolean ignoreBuildAndRevisionMismatch, Boolean buildDesignTimeFacades, String inclusionContracts, ErrorTreatment seedLoadErrorTreatment, ErrorTreatment contractLoadErrorTreatment, String[] seedTypePreferencesUnsplit, Boolean forceZeroVersionSeeds, Boolean producePdb, String partialFacadeAssemblyPath, Boolean buildPartialReferenceFacade)
     at GenFacades.Program.Main(String[] args)
  Aborted (core dumped)
/home/pi/github/wfurt-corefx2/src/shims/shims.proj(56,5): error MSB3073: The command ""/home/pi/github/wfurt-corefx2/Tools/dotnetcli/dotnet" "/home/pi/github/wfurt-corefx2/Tools/GenFacades.exe" -contracts:"/home/pi/github/wfurt-corefx2/bin/ref/netfx/mscorlib.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Configuration.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Core.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Data.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Drawing.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.IO.Compression.FileSystem.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Net.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Numerics.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Runtime.Serialization.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Security.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.ServiceProcess.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Transactions.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Web.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Windows.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Xml.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Xml.Serialization.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Xml.Linq.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.ComponentModel.DataAnnotations.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.ServiceModel.Web.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/WindowsBase.dll" @"/home/pi/github/wfurt-corefx2/bin/obj/shims/netcoreapp/genfacades.rsp"" exited with code 134.

Build FAILED.

/home/pi/github/wfurt-corefx2/src/shims/shims.proj(56,5): error MSB3073: The command ""/home/pi/github/wfurt-corefx2/Tools/dotnetcli/dotnet" "/home/pi/github/wfurt-corefx2/Tools/GenFacades.exe" -contracts:"/home/pi/github/wfurt-corefx2/bin/ref/netfx/mscorlib.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Configuration.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Core.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Data.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Drawing.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.IO.Compression.FileSystem.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Net.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Numerics.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Runtime.Serialization.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Security.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.ServiceProcess.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Transactions.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Web.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Windows.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Xml.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Xml.Serialization.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.Xml.Linq.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.ComponentModel.DataAnnotations.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/System.ServiceModel.Web.dll;/home/pi/github/wfurt-corefx2/bin/ref/netfx/WindowsBase.dll" @"/home/pi/github/wfurt-corefx2/bin/obj/shims/netcoreapp/genfacades.rsp"" exited with code 134.
    0 Warning(s)
    1 Error(s)

It seems like the correct code may be already there under #if COMPACTFX
However, there is no provision to enable that for ARM. Also the package targets ANY_CPU.
So it is really not sure up right now to provide multi-architecture support.
One option would be changing the compile-time checks to runtime option.

PEReaderAndWriter/PEReader/UnmanagedReadWrite.c:

nternal UInt32 PeekUInt32(
      uint offset
    ) {
#if COMPACTFX
      if ((int)(this.CurrentPointer + offset) % 4 != 0) return UnalignedPeekUInt32(offset);
#endif
      if (checked(this.CurrentPointer - this.Buffer + offset + sizeof(UInt32)) > this.Length)
        throw new ArgumentOutOfRangeException();
#if LITTLEENDIAN
      return *(UInt32*)(this.CurrentPointer + offset);
#elif BIGENDIAN
      uint uin = *(uint*)(this.CurrentPointer + offset);
      uin = (uin >> 16) | (uin << 16);
      uin = ((uin & 0xFF00FF00) >> 8) | ((uin & 0x00FF00FF) << 8);
      return uin;
#endif
    }

cc: @nguerrera @ericstj

[wfurt]

one more note that the ((int)(this.CurrentPointer + offset) % 4 != 0) will not work properly on arm64 as it needs to align on 8 byte boundary.