[PATCH] D49410: [PDB] Parse UDT symbols and pointers to members

[Aleksandr Urakov via Phabricator via llvm-commits]

aleksandr.urakov added inline comments.


================
Comment at: lit/SymbolFile/PDB/Inputs/ClassLayoutTest.cpp:37
+  };
+  union {  // Test unnamed union. MSVC treats it as `int a; float b;`
+    int a;
----------------
Hui wrote:
> aleksandr.urakov wrote:
> > Here is a problem. `MicrosoftRecordLayoutBuilder` asserts every field or base offset, but in our case fields `a` and `b` are treated as `struct Complex`'s fields, not `union`'s, so lldb crashes in debug on this. I can't find enough info in PDB to restore the unnamed union here. Do you have any ideas about it?
> 
> Based on MSVC cl yielded PDB, you could have full information to restore the unnamed UDT.
> 
> From my experience, PDB yielded by clang-cl  (/Z7 or /Zi) is slightly different from the one by cl.
> 
> Both contain information about forwarded unnamed UDT.
> However PDB yielded by clang-cl  more or less lacks the member information.  See below.
> 
> The CodeView info is good. Maybe you need to look at LLC?
> 
> CodeView 
>  
> ```
> FieldList (0x1044) {
>     TypeLeafKind: LF_FIELDLIST (0x1203)
>     DataMember {
>       TypeLeafKind: LF_MEMBER (0x150D)
>       AccessSpecifier: Public (0x3)
>       Type: int (0x74)
>       FieldOffset: 0x0
>       Name: a
>     }
>     DataMember {
>       TypeLeafKind: LF_MEMBER (0x150D)
>       AccessSpecifier: Public (0x3)
>       Type: float (0x40)
>       FieldOffset: 0x0
>       Name: b
>     }
>   }
> 
> Union (0x1045) {
>     TypeLeafKind: LF_UNION (0x1506)
>     MemberCount: 2
>     Properties [ (0x608)
>       HasUniqueName (0x200)
>       Nested (0x8)
>       Sealed (0x400)
>     ]
>     FieldList: <field list> (0x1044)
>     SizeOf: 4
>     Name: Complex::<unnamed-tag>
>     LinkageName: .?AT<unnamed-type-$S2>@Complex@@
>   }
> 
> ```
> 
> llvm-pdbutil  pdb  (clang-cl /z7)
> 
> (found unnamed symbol, however size = 0, they will be just ignored. See PDBASTParser.cpp #259
> The size should not be zero) 
> 
> 
> ```
>     struct Complex::<unnamed-tag> [sizeof = 0] {}
> 
>     union Complex::<unnamed-tag> [sizeof = 0] {}
> 
>  struct Complex [sizeof = 728] {
>       data +0x00 [sizeof=720] _List* array[90]
>       data +0x2d0 [sizeof=4] int x
>       data +0x2d4 [sizeof=4] int a
>       data +0x2d4 [sizeof=4] float b
>     }
> 
> ```
> 
> llvm-pdbutil pdb ( cl /z7)
> 
> ( you have full information to restore unnamed) 
> ```
> 
> struct Complex [sizeof = 728] {
>       data +0x00 [sizeof=720] _List* array[90]
>       data +0x2d0 [sizeof=4] int x
>       data +0x2d4 [sizeof=4] int a
>       data +0x2d4 [sizeof=4] float b
>     }
> 
>     Total padding 3 bytes (25% of class size)
>     Immediate padding 3 bytes (25% of class size)
> 
>     struct Complex::<unnamed-tag> [sizeof = 4] {
>       data +0x00 [sizeof=4] int x
>     }
> 
>     union Complex::<unnamed-tag> [sizeof = 4] {
>       data +0x00 [sizeof=4] int a
>       data +0x00 [sizeof=4] float b
>     }
> ```
> 
> 
Thank you! But what means `LLC`?


https://reviews.llvm.org/D49410