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

[Aleksandr Urakov via Phabricator via lldb-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;
----------------
aleksandr.urakov wrote:
> 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`?
I have figured that out, sorry. I usually use disassembly tools for this purpose.


https://reviews.llvm.org/D49410