.net - What are F#'s FSharp.Core.optdata and FSharp.Core.sigdata files?

Question

Both files seem to reside in F#'s directory, along with FSharp.Core.dll. Both files seem to be a constant source of trouble if one forgets to put them together with FSharp.Core.dll. They seem to be binary files so I wasn't able to uncover their purpose.

I googled a bit both files but there doesn't seem to be a clear answer to my question. So..what is their function in F#?

Answer 1

Optdata is definitely optimisation data, it is written as part of the EncodeOptimizationData function in the compiler. FSharp.Core has this information stored in an external file rather than embedded in the resource manifest.

sigdata is encoded with EncodeInterfaceData and contains information about the signatures/interfaces for the F# types. FSharp.Core, FSharp.Compiler.Silverlight and FSharp.LanguageService.Compiler all have this information stored in an external file rather than embedded in the resource manifest.

As FSharp.Core does not contain either of these in its resource manifest they have to be present externally, Im not sure of this reason though.

User produced F# files, when compiled, have this information encoded into the resource manifest, you can see this if you look at the metadata.