When a class indirectly inherits from a class with virtual bases, it
will get an `LF_IVBCLASS` record in its fieldlist, even though it
doesn't directly inherit that class.
In the following example, `UserUser` inherits from `User`, which
virtually inherits from `VBase`:
```cpp
struct User : public virtual VBase {};
struct UserUser : public User {};
```
For this we get
```
0x1015 | LF_FIELDLIST [size = 72]
- LF_BCLASS
type = 0x1002 (-> 0x102A), offset = 0, attrs = public
- LF_IVBCLASS
base = 0x1003, vbptr = 0x1005, vbptr offset = 0, vtable index = 1
attrs = public (...)
0x1016 | LF_STRUCTURE [size = 48] `UserUser`
unique name: `.?AUUserUser@@`
vtable: <no type>, base list: <no type>, field list: 0x1015
options: has ctor / dtor | has unique name | overloaded operator | overloaded operator=, sizeof 16
0x1029 | LF_FIELDLIST [size = 56]
- LF_VBCLASS
base = 0x1003, vbptr = 0x1005, vbptr offset = 0, vtable index = 1
attrs = public (...)
0x102A | LF_STRUCTURE [size = 40] `User`
unique name: `.?AUUser@@`
vtable: <no type>, base list: <no type>, field list: 0x1029
options: has ctor / dtor | has unique name | overloaded operator | overloaded operator=, sizeof 16
```
If I understand correctly, then `LF_IVBCLASS` indicates that if this
class (e.g. `UserUser`) is created as the most derived object, it will
host the class (e.g. `VBase`).
The VS debugger actually shows this as a separate field. LLDB on the
other hand doesn't, so I removed it.
---------
Co-authored-by: Zequan Wu <zequanwu@google.com>
This test was failing with the native plugin due to two reasons:
1. The static `C::abc` was printed as `(int) ::C::abc = 123`
2. The order of the base classes of [`C`
(`List::Value`)](b7e4edca3d/lldb/test/Shell/SymbolFile/PDB/Inputs/UdtLayoutTest.cpp (L30))
is different between DIA and the native plugin. I don't know how the
order in the DIA plugin is determined - it prints `B<0>`, `B<1>`,
`B<2>`, `B<3>`, `A`. The native plugin follows the order of the bases in
memory and prints `B<2>`, `B<3>`, `A`, `B<0>`, `B<1>` (last three are
the virtual bases).
<details><summary>Class layout of C</summary>
```
class C size(88):
+---
0 | +--- (base class B<2>)
0 | | {vbptr}
8 | | _a
9. | | _b (bitstart=3,nbits=6)
11 | | _c
| +---
15 | +--- (base class B<3>)
15 | | {vbptr}
23 | | _a
24. | | _b (bitstart=3,nbits=6)
26 | | _c
| +---
| <alignment member> (size=2)
32 | _x
36 | _y
38 | _z
| <alignment member> (size=1)
| <alignment member> (size=2)
+---
+--- (virtual base A)
40 | {vfptr}
48 | U _u
| <alignment member> (size=4)
+---
+--- (virtual base B<0>)
56 | {vbptr}
64 | _a
65. | _b (bitstart=3,nbits=6)
67 | _c
+---
+--- (virtual base B<1>)
71 | {vbptr}
79 | _a
80. | _b (bitstart=3,nbits=6)
82 | _c
+---
```
</details>
I split the tests for the plugins for better readability.
