The PDB checksum checking doesn't work for Windows PDBs

[Mike McLaughlin]

There is very subtle bug in the Windows PDB key generator that caused the pdb checksum list never to be passed to the SymbolStoreKey constructor (one of the closing parentheses is in the wrong place causing pdbChecksums to be passed to the string.Format instead of BuildKey).

PDBFileKeyGenerator.cs line 52:

-       return BuildKey(path, string.Format("{0}{1:x}", signature.ToString("N"), age, pdbChecksums));
+       return BuildKey(path, string.Format("{0}{1:x}", signature.ToString("N"), age), clrSpecialFile: false, pdbChecksums);

Once this was fixed, symbol downloads for Windows PDBs (i.e. Microsoft.Extensions.Hosting.Abstractions.ni.pdb) started failing because ChecksumValidator.cs seems to only handle portable PDBs:

        private static uint GetPdbStreamOffset(Stream pdbStream)
        {
            pdbStream.Position = 0;
            using (var reader = new BinaryReader(pdbStream, Encoding.UTF8, leaveOpen: true))
            {
                pdbStream.Seek(4 + // Signature
                               2 + // Version Major
                               2 + // Version Minor
                               4,  // Reserved)
                               SeekOrigin.Begin);

                // skip the version string
                uint versionStringSize = reader.ReadUInt32();     <<------- exception

                pdbStream.Seek(versionStringSize, SeekOrigin.Current);

[Gregg Miskelly]

FYI I don't think anything supports PDB checksums for Windows PDBs.

[Tomáš Matoušek]

I heard that C++ now emits PDB checksums, but Roslyn does not currently: dotnet/roslyn#24429

[Gregg Miskelly]

I double checked the VS debugger sources, and VS will ignore checksums when searching for non-portable PDBs. I don't know if symsrv.dll wound up added support, but, at least originally, it also only supported portable PDBs.