I was debugging some issues with the help of Application Verifier and WinDbg. Since I was onsite I did not have any access to Microsoft’s private symbol servers, so I was using the public symbol server (http://msdl.microsoft.com/download/symbols). On executing the !avrf extension command in WinDbg I was presented with the following error message in WinDbg:

***    Your debugger is not using the correct symbols                 ***
***                                                                   ***
***    In order for this command to work properly, your symbol path   ***
***    must point to .pdb files that have full type information.      ***
***                                                                   ***
***    Certain .pdb files (such as the public OS symbols) do not      ***
***    contain the required information.  Contact the group that      ***
***    provided you with these symbols if you need this command to    ***
***    work.                                                          ***
***                                                                   ***
***    Type referenced: vfbasics!_AVRF_EXCEPTION_LOG_ENTRY                ***

It turns out that my WinDbg symbol path was as follows, and due to it pointing just to the public symbol server it was loading public symbols for vfbasics.dll:

0:001> .sympath
Symbol search path is: SRV*c:localsymbols*http://msdl.microsoft.com/download/symbols
Expanded Symbol search path is: srv*c:localsymbols*http://msdl.microsoft.com/download/symbols
0:001> lml
start             end                 module name
00000000`76dc0000 00000000`76f68000   ntdll      (pdb symbols)          c:localsymbolsntdll.pdbFDAD9EE7D6E44F4F9672ECB401A802192ntdll.pdb
000007fe`f0e50000 000007fe`f0ebe000   verifier   (pdb symbols)          c:localsymbolsverifier.pdb43FCE2D63C4544F9B1C67110EB3406951verifier.pdb
000007fe`f1660000 000007fe`f1693000   vrfcore    (pdb symbols)          c:localsymbolsvrfcore.pdb751D23CCD6504794AF2F18C1E547FE371vrfcore.pdb
000007fe`f28e0000 000007fe`f292a000   vfbasics   (pdb symbols)          c:localsymbolsvfbasics.pdb1ABCDFEFF9F4602A7F055801457A7D61vfbasics.pdb

To resolve the issue, I explicitly pre-pended the path to private symbols for vfbasics (which is c:windowssystem32 or in general %WINDIR%System32:

.sympath c:windowssystem32*SRV*c:localsymbols*http://msdl.microsoft.com/download/symbols

.reload

ld vfbasics

0:001> lml
start             end                 module name
00000000`76dc0000 00000000`76f68000   ntdll      (export symbols)       C:WindowsSYSTEM32ntdll.dll
000007fe`f28e0000 000007fe`f292a000   vfbasics   (private pdb symbols)  C:WindowsSYSTEM32vfbasics.pdb

Then !avrf works just fine!

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