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Possible bug with attribute IL emit
f#

There appears to be something wrong either with the way System.Configuration parses attributes, or the way F# emits them. Here's an odd way to cause an exception:

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#r "System.Configuration"

open System.Configuration    

type TestElement1() =

    inherit ConfigurationElement()

    

    static let properties = ConfigurationPropertyCollection()

    static let add p = properties.Add p; p

    

    static let value = add (ConfigurationProperty("value", typeof<int>, 42, ConfigurationPropertyOptions.IsRequired))

    

    member x.Value

        with get() = base.[value] :?> int

        and set (v:int) = base.[value] <- v

        

    override x.Properties = properties

   

type TestElement2() =

    inherit ConfigurationElement()

    

    [<ConfigurationProperty("value", DefaultValue = 42, IsRequired=true)>]

    member x.Value

        with get() = base.["value"] :?> int

        and set (v:int) = base.["value"] <- v

        

let t1 = TestElement1();;

printfn "TestElement1: %A" t1.Value // This doesn't crash

let t2 = TestElement2();;

printfn "TestElement2: %A" t2.Value // This crashes

And here's the exception:

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> System.Reflection.CustomAttributeFormatException: Binary format of the specified custom attribute was invalid.

   at System.Reflection.CustomAttribute._GetPropertyOrFieldData(IntPtr pModule, Byte** ppBlobStart, Byte* pBlobEnd, String& name, Boolean& bIsProperty, Type& type, Object& value)

   at System.Reflection.CustomAttribute.GetPropertyOrFieldData(Module module, IntPtr& blobStart, IntPtr blobEnd, String& name, Boolean& isProperty, Type& type, Object& value)

   at System.Reflection.CustomAttribute.GetCustomAttributes(Module decoratedModule, Int32 decoratedMetadataToken, Int32 pcaCount, RuntimeType attributeFilterType, Boolean mustBeInheritable, IList derivedAttributes)

   at System.Reflection.CustomAttribute.GetCustomAttributes(RuntimePropertyInfo property, RuntimeType caType)

   at System.Reflection.RuntimePropertyInfo.GetCustomAttributes(Type attributeType, Boolean inherit)

   at System.Attribute.InternalGetCustomAttributes(PropertyInfo element, Type type, Boolean inherit)

   at System.Attribute.GetCustomAttributes(MemberInfo element, Type type, Boolean inherit)

   at System.Attribute.GetCustomAttribute(MemberInfo element, Type attributeType, Boolean inherit)

   at System.Configuration.ConfigurationElement.CreateConfigurationPropertyFromAttributes(PropertyInfo propertyInformation)

   at System.Configuration.ConfigurationElement.CreatePropertyBagFromType(Type type)

   at System.Configuration.ConfigurationElement.PropertiesFromType(Type type, ConfigurationPropertyCollection& result)

   at System.Configuration.ConfigurationElement.get_Properties()

   at System.Configuration.ConfigurationElement.get_Item(String propertyName)

   at FSI_0054.TestElement2.get_Value() in C:\Users\rei\Documents\Visual Studio 2008\Projects\SessionConfiguration.fs:line 81

   at <StartupCode$FSI_0056>.$FSI_0056.main@()

stopped due to error

The external behavior of the code is the same between TestElement1 and TestElement2, though of course the workings within System.Configuration are presumably quite different. But judging from the stack trace, it might be a safe bet to say that F# is emitting strange IL that System.Reflection sometimes doesn't like for whatever reason.

.Reply
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Hi reinux -

The code you included appears to have been partly corrupted, so I'm not sure what the attribute decoration on TestElement2.Value looked like in your original code.

When I try this with ConfigurationPropertyAttribute("value"), the code appears to run correctly for me with VS2010 Beta1.

If you are still seeing problems, could you send the attribute annotation you are using?

Thanks,

Luke

By on 9/21/2009 10:47 PM ()Reply
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Sorry about that.

The attribute should read: ConfigurationProperty("value", DefaultValue = 42, IsRequired=true)

I think that the result should be the same, so it's probably safe to assume that it's been remedied in VS2010.

By on 9/22/2009 1:05 AM ()Reply

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