Interesting bugs – MSB3246: Resolved file has a bad image, no metadata, or is otherwise inaccessible. Image is too small.

I got a very strange warning recently when building a .NET Core app with "dotnet build."

MSB3246: Resolved file has a bad image, no metadata, or is otherwise inaccessible. 

Image is too small.

Eek! It's clear, in that something is "too small" but what? A file I guess? Maybe it's the wrong size?

The error code is MSB3246 which is nice and googleable/searchable but it was confusing because I couldn't figure our what file specifically. It just felt vague.

BUT!

I had recently been overclocking my machine (overly aggressively, gulp, about 40%) and had a very nasty hard reboot. As a result I had a few dozen files get orphaned - specifically the files were zero'ed out! Zero is small, right?

Turns out you can pass parameters over to MSBuild from "dotnet build" and see what MSBuild is doing internally. For example, you could

/fileLoggerParameters:verbosity=diagnostic

but that's long. So how about:

dotnet build /flp:v=diag

Cool. What deep logging do I see now?

Primary reference "deliberately.zero.bytes.dll". (TaskId:41)

13:36:52.397 1:7>C:Program Filesdotnetsdk2.1.400Microsoft.Common.CurrentVersion.targets(2110,5): warning MSB3246: Resolved file has a bad image, no metadata, or is otherwise inaccessible. Image is too small. [S:workzero-byte-refzero-byte-ref.csproj]

 Resolved file path is "S:workzero-byte-refdeliberately.zero.bytes.dll". (TaskId:41)

 Reference found at search path location "{RawFileName}". (TaskId:41)

Now with "verbose" turned on I can see that one of the references is zero'ed out/corrupted/bad. I reinstalled .NET Core in my case and doubled checked all the DLLs/Assemblies that I was bringing in - I also ran chkdsk /f - and I was back in business!

I hope this helps someone who might stumble on error MSB3246 and wonder what's up.

Even better, thanks to Rainer Sigwald who filed a bug against MSBuild to update the error message to be more clear. In the future I'll be able to debug this without changing verbosity!

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