[PATCH] D30952: Native PDB reader was swapping module and object file names

[Zachary Turner via Phabricator via llvm-commits]

zturner added a comment.

So here <https://github.com/Microsoft/microsoft-pdb/blob/master/PDB/dbi/dbi.h#L1223-L1224> is why I think it was originally correct:

The method that computes the address of the first character of the "object file name" first gets the address of the "module name", then adds the length of the module name plus 1 byte for the null terminator.  So at least in the reference code here, module name comes before object file name.

It could just be that they chose poor names themselves, or are using the terms incorrectly.  However, when I run `llvm-pdbdump pretty` on the file `empty.pdb` that is in the test file Inputs directory, it gives me this:

  D:\src\llvmbuild\ninja>bin\llvm-pdbdump.exe pretty -compilands d:\src\llvm-mono\llvm\test\DebugInfo\pdb\Inputs\empty.pdb
  Summary for d:\src\llvm-mono\llvm\test\DebugInfo\pdb\Inputs\empty.pdb
    Size: 102400 bytes
    Guid: {0B355641-86A0-A249-896F-9988FAE52FF0}
    Age: 1
    Attributes: HasPrivateSymbols
  ---COMPILANDS---
    d:\src\llvm\test\DebugInfo\PDB\Inputs\empty.obj
    * Linker *

The strings that are printed there are obtained by calling IDiaSymbol::get_Name().  For Compiland Symbols <https://msdn.microsoft.com/en-us/library/944b51dy.aspx>, `get_Name()` is documented as returning "the name of the compiland's object file" and `get_LibraryName()` is documented as returning "Name of the library or object file where object was loaded from."  I never call `get_libraryName()` anywhere, but I think it's safe to assume that `get_name()` returns either the "module name" or the "object name", and `get_libraryName` returns the other.

Comparing to `llvm-pdbdump raw`, I get this:

  D:\src\llvmbuild\ninja>bin\llvm-pdbdump.exe raw -modules d:\src\llvm-mono\llvm\test\DebugInfo\pdb\Inputs\empty.pdb
  DBI Stream {
    Dbi Version: 19990903
    Age: 1
    Incremental Linking: Yes
    Has CTypes: No
    Is Stripped: No
    Machine Type: x86
    Symbol Record Stream Index: 8
    Public Symbol Stream Index: 7
    Global Symbol Stream Index: 6
    Toolchain Version: 12.0
    mspdb120.dll version: 12.0.31101
    Modules [
      {
        Name: d:\src\llvm\test\DebugInfo\PDB\Inputs\empty.obj
        Debug Stream Index: 12
        Object File Name: d:\src\llvm\test\DebugInfo\PDB\Inputs\empty.obj
        Num Files: 1
        Source File Name Idx: 0
        Pdb File Name Idx: 0
        Line Info Byte Size: 0
        C13 Line Info Byte Size: 88
        Symbol Byte Size: 208
        Type Server Index: 0
        Has EC Info: No
      }
      {
        Name: * Linker *
        Debug Stream Index: 14
        Object File Name:
        Num Files: 0
        Source File Name Idx: 0
        Pdb File Name Idx: 1
        Line Info Byte Size: 0
        C13 Line Info Byte Size: 0
        Symbol Byte Size: 516
        Type Server Index: 0
        Has EC Info: No
      }
    ]
  }

So what I'm referring to as "name" and "object file name" appear to match up with the reference implementation.  I'm not sure what the best thing to do here is, but having the variables be called the reverse of what they're called in the reference implementation could leave to even more confusion when someone else comes along and tries to understand the code.

Thoughts?


https://reviews.llvm.org/D30952