[LLDB][PDB] Run UDT layout test with native PDB too #159769

Nerixyz · 2025-09-19T12:31:10Z

This test was failing with the native plugin due to two reasons:

The static C::abc was printed as (int) ::C::abc = 123

The order of the base classes of C (List::Value) 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).

Class layout of C

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
        +---

I split the tests for the plugins for better readability.

llvmbot · 2025-09-19T12:31:39Z

@llvm/pr-subscribers-lldb

Author: nerix (Nerixyz)

Changes

This test was failing with the native plugin due to two reasons:

The static C::abc was printed as (int) ::C::abc = 123

The order of the base classes of C (List::Value) 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&lt;2&gt;)
0       | | {vbptr}
8       | | _a
9.      | | _b (bitstart=3,nbits=6)
11      | | _c
        | +---
15      | +--- (base class B&lt;3&gt;)
15      | | {vbptr}
23      | | _a
24.     | | _b (bitstart=3,nbits=6)
26      | | _c
        | +---
        | &lt;alignment member&gt; (size=2)
32      | _x
36      | _y
38      | _z
        | &lt;alignment member&gt; (size=1)
        | &lt;alignment member&gt; (size=2)
        +---
        +--- (virtual base A)
40      | {vfptr}
48      | U _u
        | &lt;alignment member&gt; (size=4)
        +---
        +--- (virtual base B&lt;0&gt;)
56      | {vbptr}
64      | _a
65.     | _b (bitstart=3,nbits=6)
67      | _c
        +---
        +--- (virtual base B&lt;1&gt;)
71      | {vbptr}
79      | _a
80.     | _b (bitstart=3,nbits=6)
82      | _c
        +---

</details>

I updated the checks to permit outputs from both plugins.

Full diff: https://github.com/llvm/llvm-project/pull/159769.diff

1 Files Affected:

(modified) lldb/test/Shell/SymbolFile/PDB/udt-layout.test (+59-47)

diff --git a/lldb/test/Shell/SymbolFile/PDB/udt-layout.test b/lldb/test/Shell/SymbolFile/PDB/udt-layout.test
index bc68539e25ec1..ed943bc9fb513 100644
--- a/lldb/test/Shell/SymbolFile/PDB/udt-layout.test
+++ b/lldb/test/Shell/SymbolFile/PDB/udt-layout.test
@@ -1,51 +1,63 @@
 REQUIRES: target-windows, lld
 RUN: %build --compiler=clang-cl --output=%t.exe %S/Inputs/UdtLayoutTest.cpp
-RUN: %lldb -b -s %S/Inputs/UdtLayoutTest.script -- %t.exe | FileCheck %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=0 %lldb -b -s %S/Inputs/UdtLayoutTest.script -- %t.exe | FileCheck %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 %lldb -b -s %S/Inputs/UdtLayoutTest.script -- %t.exe | FileCheck %s
 
-CHECK:(int) C::abc = 123
+CHECK:(int) {{(::)?}}C::abc = 123
 CHECK:(List[16]) ls = {
-CHECK:  [15] = {
-CHECK:    Prev = nullptr
-CHECK:    Next = nullptr
-CHECK:    Value = {
-CHECK:      B<0> = {
-CHECK:        A = {
-CHECK:          _u = (_u1 = '\x02', _u2 = 2, _u3 = 2)
-CHECK:        }
-CHECK:        _a = '\x01'
-CHECK:        _b = 2
-CHECK:        _c = 3
-CHECK:      }
-CHECK:      B<1> = {
-CHECK:        A = {
-CHECK:          _u = (_u1 = '\x02', _u2 = 2, _u3 = 2)
-CHECK:        }
-CHECK:        _a = '\x02'
-CHECK:        _b = 4
-CHECK:        _c = 6
-CHECK:      }
-CHECK:      B<2> = {
-CHECK:        A = {
-CHECK:          _u = (_u1 = '\x02', _u2 = 2, _u3 = 2)
-CHECK:        }
-CHECK:        _a = '\x03'
-CHECK:        _b = 6
-CHECK:        _c = 9
-CHECK:      }
-CHECK:      B<3> = {
-CHECK:        A = {
-CHECK:          _u = (_u1 = '\x02', _u2 = 2, _u3 = 2)
-CHECK:        }
-CHECK:        _a = '\x04'
-CHECK:        _b = 8
-CHECK:        _c = 12
-CHECK:      }
-CHECK:      A = {
-CHECK:        _u = (_u1 = '\x02', _u2 = 2, _u3 = 2)
-CHECK:      }
-CHECK:      _x = 5
-CHECK:      _y = 10
-CHECK:      _z = '\x0f'
-CHECK:    }
-CHECK:  }
-CHECK:}
+
+CHECK:       [14] = {
+CHECK-NEXT:    Prev = nullptr
+CHECK-NEXT:    Next = nullptr
+CHECK-NEXT:    Value = {
+CHECK:           B<0> = {
+CHECK-NEXT:        A = {
+CHECK-NEXT:          _u = (_u1 = '\x02', _u2 = 2, _u3 = 2)
+CHECK-NEXT:        }
+CHECK-NEXT:        _a = '\x01'
+CHECK-NEXT:        _b = 2
+CHECK-NEXT:        _c = 3
+CHECK-NEXT:      }
+CHECK-NEXT:      B<1> = {
+CHECK-NEXT:        A = {
+CHECK-NEXT:          _u = (_u1 = '\x02', _u2 = 2, _u3 = 2)
+CHECK-NEXT:        }
+CHECK-NEXT:        _a = '\x02'
+CHECK-NEXT:        _b = 4
+CHECK-NEXT:        _c = 6
+CHECK-NEXT:      }
+CHECK:           _x = 5
+CHECK-NEXT:      _y = 10
+CHECK-NEXT:      _z = '\x0f'
+CHECK-NEXT:    }
+CHECK-NEXT:  }
+
+CHECK-NEXT:  [15] = {
+CHECK-NEXT:    Prev = nullptr
+CHECK-NEXT:    Next = nullptr
+CHECK-NEXT:    Value = {
+CHECK:           B<2> = {
+CHECK-NEXT:        A = {
+CHECK-NEXT:          _u = (_u1 = '\x02', _u2 = 2, _u3 = 2)
+CHECK-NEXT:        }
+CHECK-NEXT:        _a = '\x03'
+CHECK-NEXT:        _b = 6
+CHECK-NEXT:        _c = 9
+CHECK-NEXT:      }
+CHECK-NEXT:      B<3> = {
+CHECK-NEXT:        A = {
+CHECK-NEXT:          _u = (_u1 = '\x02', _u2 = 2, _u3 = 2)
+CHECK-NEXT:        }
+CHECK-NEXT:        _a = '\x04'
+CHECK-NEXT:        _b = 8
+CHECK-NEXT:        _c = 12
+CHECK-NEXT:      }
+CHECK-NEXT:      A = {
+CHECK-NEXT:        _u = (_u1 = '\x02', _u2 = 2, _u3 = 2)
+CHECK-NEXT:      }
+CHECK:           _x = 5
+CHECK-NEXT:      _y = 10
+CHECK-NEXT:      _z = '\x0f'
+CHECK-NEXT:    }
+CHECK-NEXT:  }
+CHECK-NEXT:}

Michael137 · 2025-09-22T09:23:29Z

lldb/test/Shell/SymbolFile/PDB/udt-layout.test

-CHECK:  }
-CHECK:}
+
+CHECK:       [14] = {


Can we just have two CHECK prefixes. One for the native and one for the DIA plugin. And check the respective layouts.

I find that less confusing to someone reading this file for the first time

This would fail if LLDB is compiled without DIA support. In that case, the native plugin would always be used, and it would fail the check intended for DIA.

I could also mark the whole test as DIA-only and add a second udt-layout-native.test for the native plugin.

Does LLDB complain if a user requests the DIA plugin but LLDB was compiled without DIA support? If not, I think it's worth investigating

I could also mark the whole test as DIA-only and add a second udt-layout-native.test for the native plugin.

Yea I would prefer that. It would be nice if as many of the NativePDB tests stayed in the NativePDB subdirectory as possible. That way we don't need to worry about losing coverage when we delete the PDB plugin

I added a separate test to the native plugin now.

Does LLDB complain if a user requests the DIA plugin but LLDB was compiled without DIA support? If not, I think it's worth investigating

This isn't the case right now. I'll take a look at printing a warning.

Michael137

great thanks!

If LLDB was built without the DIA SDK and the DIA reader is explicitly requested (through `LLDB_USE_NATIVE_PDB_READER=0` or `settings set plugin.symbol-file.pdb.reader dia`), LLDB should print a warning, because it will use the native reader in any case (#159769 (comment)). This PR adds the warning and a test when LLDB is not built with the SDK on Windows. I don't think any builder runs this configuration, as there are still five failing tests. I tested this locally with and without the SDK.

…ble (#160067) If LLDB was built without the DIA SDK and the DIA reader is explicitly requested (through `LLDB_USE_NATIVE_PDB_READER=0` or `settings set plugin.symbol-file.pdb.reader dia`), LLDB should print a warning, because it will use the native reader in any case (llvm/llvm-project#159769 (comment)). This PR adds the warning and a test when LLDB is not built with the SDK on Windows. I don't think any builder runs this configuration, as there are still five failing tests. I tested this locally with and without the SDK.

Nerixyz requested a review from JDevlieghere as a code owner September 19, 2025 12:31

llvmbot added the lldb label Sep 19, 2025

Michael137 reviewed Sep 22, 2025

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[LLDB][PDB] Run UDT layout test with native PDB too

d2c6336

Nerixyz force-pushed the fix/npdb-udt-layout branch from ccf7987 to d2c6336 Compare September 22, 2025 09:58

Nerixyz mentioned this pull request Sep 22, 2025

[LLDB][PDB] Warn if DIA plugin is requested but not available #160067

Merged

Michael137 approved these changes Sep 22, 2025

View reviewed changes

Nerixyz merged commit e08d8e3 into llvm:main Sep 23, 2025
9 checks passed

Nerixyz deleted the fix/npdb-udt-layout branch November 7, 2025 14:16

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[LLDB][PDB] Run UDT layout test with native PDB too #159769

[LLDB][PDB] Run UDT layout test with native PDB too #159769

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[LLDB][PDB] Run UDT layout test with native PDB too #159769

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Nerixyz commented Sep 19, 2025 •

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