PDBs: What is the C:\Windows\Symbols\dll directory?

Question

I know about debugging symbols (PDBs), the MS Symbol Server and the caching of symbols.

What I do not get is which symbols (by whom) go into the C:\Windows\Symbols\dll directory. It doesn't seem C:\Windows\Symbols\dll has anything to do with MSSS caching.

Example, my version of this directory contains:

C:\Windows\Symbols\dll>dir

21.02.2013  16:47    <DIR>          .
21.02.2013  16:47    <DIR>          ..
18.02.2011  16:18         3.854.336 atl100.i386.pdb
18.02.2011  18:23        25.300.992 mfc100.i386.pdb
18.02.2011  18:22        28.938.240 mfc100d.i386.pdb
18.02.2011  18:23        25.473.024 mfc100u.i386.pdb
18.02.2011  18:23        29.241.344 mfc100ud.i386.pdb
18.02.2011  18:26         4.386.816 mfcm100.i386.pdb
18.02.2011  18:26         4.452.352 mfcm100d.i386.pdb
18.02.2011  18:26         4.403.200 mfcm100u.i386.pdb
18.02.2011  18:26         4.468.736 mfcm100ud.i386.pdb
18.02.2011  18:05            13.824 Microsoft.Workflow.ExpressionEvaluation.pdb
18.02.2011  16:18         3.755.008 msvcp100.i386.pdb
18.02.2011  16:18         4.377.600 msvcp100d.i386.pdb
18.02.2011  16:17         8.875.008 msvcr100.i386.pdb
18.02.2011  16:18         7.900.160 msvcr100d.i386.pdb
18.02.2011  18:26         1.699.840 vcomp100.i386.pdb
18.02.2011  18:26         1.798.144 vcomp100d.i386.pdb

But no other files, although this machine has both VS2005 and VS2010 installed. I always thought the files get put there by VS, but since the ...80... versions are missing (which I have on other machines), it seems VS2005 didn't put them there.

Answer 1

These are pdbs that help you step through the MFC code. This is being put in here by VS and more specifically the VC++ installation which would be a part of your VS install.