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

[Zachary Turner via llvm-commits]

I think the problem is in lld, we don’t emit S_UDT symbols because it
caused weird problems in WinDbg.  There’s a comment explaining it in
PDB.cpp.  But after some recent fixes this may just work.  So we should
probably try again to emit the S_UDT in lld, I think that should fix it

On Fri, Jul 20, 2018 at 1:01 AM Hui Huang via Phabricator <
reviews at reviews.llvm.org> wrote:

> Hui 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:
> > 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
>     }
> ```
>
>
>
>
> https://reviews.llvm.org/D49410
>
>
>
>
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