[LLDB][NativePDB] Resolve declaration for tag types #152579

Nerixyz · 2025-08-07T19:12:07Z

Tag types like stucts or enums didn't have a declaration attached to them. The source locations are present in the IPI stream in LF_UDT_MOD_SRC_LINE records:

   0x101F | LF_UDT_MOD_SRC_LINE [size = 18, hash = 0x1C63]
            udt = 0x1058, mod = 3, file = 1, line = 0
   0x2789 | LF_UDT_MOD_SRC_LINE [size = 18, hash = 0x1E5A]
            udt = 0x1253, mod = 35, file = 93, line = 17069

The file is an ID in the string table /names:

     ID | String
      1 | '\<unknown>'
     12 | 'D:\a\_work\1\s\src\ExternalAPIs\WindowsSDKInc\c\Include\10.0.22621.0\um\wingdi.h'
     93 | 'D:\a\_work\1\s\src\ExternalAPIs\WindowsSDKInc\c\Include\10.0.22621.0\um\winnt.h'

Here, we're not interested in mod. This would indicate which module contributed the UDT.

I was looking at Rustc's PDB and found that it uses <unknown> for some types, so I added a check for that.

This makes two DIA PDB shell tests to work with the native PDB plugin.

llvmbot · 2025-08-07T19:12:41Z

@llvm/pr-subscribers-lldb

Author: nerix (Nerixyz)

Changes

Tag types like stucts or enums didn't have a declaration attached to them. The source locations are present in the IPI stream in LF_UDT_MOD_SRC_LINE records:

   0x101F | LF_UDT_MOD_SRC_LINE [size = 18, hash = 0x1C63]
            udt = 0x1058, mod = 3, file = 1, line = 0
   0x2789 | LF_UDT_MOD_SRC_LINE [size = 18, hash = 0x1E5A]
            udt = 0x1253, mod = 35, file = 93, line = 17069

The file is an ID in the string table /names:

     ID | String
      1 | '\&lt;unknown&gt;'
     12 | 'D:\a\_work\1\s\src\ExternalAPIs\WindowsSDKInc\c\Include\10.0.22621.0\um\wingdi.h'
     93 | 'D:\a\_work\1\s\src\ExternalAPIs\WindowsSDKInc\c\Include\10.0.22621.0\um\winnt.h'

Here, we're not interested in mod. This would indicate which module contributed the UDT.

I was looking at Rustc's PDB and found that it uses <unknown> for some types, so I added a check for that.

This makes two DIA PDB shell tests to work with the native PDB plugin.

Full diff: https://github.com/llvm/llvm-project/pull/152579.diff

4 Files Affected:

(modified) lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp (+54-3)
(modified) lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.h (+10)
(modified) lldb/test/Shell/SymbolFile/PDB/class-layout.test (+11-1)
(modified) lldb/test/Shell/SymbolFile/PDB/enums-layout.test (+6)

diff --git a/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp b/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp
index dcea33dd9f854..684d46d1da4e6 100644
--- a/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp
+++ b/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp
@@ -643,8 +643,7 @@ SymbolFileNativePDB::CreateClassStructUnion(PdbTypeSymId type_id,
 
   std::string uname = GetUnqualifiedTypeName(record);
 
-  // FIXME: Search IPI stream for LF_UDT_MOD_SRC_LINE.
-  Declaration decl;
+  Declaration decl = ResolveUdtDeclaration(type_id);
   return MakeType(toOpaqueUid(type_id), ConstString(uname), size, nullptr,
                   LLDB_INVALID_UID, Type::eEncodingIsUID, decl, ct,
                   Type::ResolveState::Forward);
@@ -667,7 +666,7 @@ lldb::TypeSP SymbolFileNativePDB::CreateTagType(PdbTypeSymId type_id,
                                                 CompilerType ct) {
   std::string uname = GetUnqualifiedTypeName(er);
 
-  Declaration decl;
+  Declaration decl = ResolveUdtDeclaration(type_id);
   TypeSP underlying_type = GetOrCreateType(er.UnderlyingType);
 
   return MakeType(
@@ -2441,3 +2440,55 @@ SymbolFileNativePDB::GetContextForType(TypeIndex ti) {
   }
   return ctx;
 }
+
+void SymbolFileNativePDB::CacheUdtDeclarations() {
+  if (m_has_cached_udt_declatations)
+    return;
+  m_has_cached_udt_declatations = true;
+
+  for (CVType cvt : m_index->ipi().typeArray()) {
+    if (cvt.kind() != LF_UDT_MOD_SRC_LINE)
+      continue;
+
+    UdtModSourceLineRecord udt_mod_src;
+    llvm::cantFail(TypeDeserializer::deserializeAs(cvt, udt_mod_src));
+    // Some types might be contributed by multiple modules. We assume that they
+    // all point to the same file and line because we can only provide one
+    // location.
+    m_udt_declarations.try_emplace(udt_mod_src.UDT,
+                                   udt_mod_src.SourceFile.getIndex(),
+                                   udt_mod_src.LineNumber);
+  }
+}
+
+Declaration SymbolFileNativePDB::ResolveUdtDeclaration(PdbTypeSymId type_id) {
+  CacheUdtDeclarations();
+  auto it = m_udt_declarations.find(type_id.index);
+  if (it == m_udt_declarations.end())
+    return Declaration();
+
+  auto [file_index, line] = it->second;
+  auto string_table = m_index->pdb().getStringTable();
+  if (!string_table) {
+    LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), string_table.takeError(),
+                   "Failed to get string table: {0}");
+    return Declaration();
+  }
+
+  llvm::Expected<llvm::StringRef> file_name =
+      string_table->getStringTable().getString(file_index);
+  if (!file_name) {
+    LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), file_name.takeError(),
+                   "Failed to get string with id {1}: {0}", file_index);
+    return Declaration();
+  }
+
+  // rustc sets the filename to "<unknown>" for some files
+  if (*file_name == "\\<unknown>")
+    return Declaration();
+
+  FileSpec::Style style = file_name->starts_with("/")
+                              ? FileSpec::Style::posix
+                              : FileSpec::Style::windows;
+  return Declaration(FileSpec(*file_name, style), line);
+}
diff --git a/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.h b/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.h
index eda375d4cebe7..2e8270794af1a 100644
--- a/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.h
+++ b/lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.h
@@ -260,6 +260,9 @@ class SymbolFileNativePDB : public SymbolFileCommon {
 
   std::vector<CompilerContext> GetContextForType(llvm::codeview::TypeIndex ti);
 
+  void CacheUdtDeclarations();
+  Declaration ResolveUdtDeclaration(PdbTypeSymId type_id);
+
   llvm::BumpPtrAllocator m_allocator;
 
   lldb::addr_t m_obj_load_address = 0;
@@ -281,6 +284,13 @@ class SymbolFileNativePDB : public SymbolFileCommon {
   llvm::DenseMap<llvm::codeview::TypeIndex, llvm::codeview::TypeIndex>
       m_parent_types;
 
+  /// type index -> (filename index, line)
+  ///
+  /// The filename index is an index into the `/names` section (string table)
+  llvm::DenseMap<llvm::codeview::TypeIndex, std::pair<uint32_t, uint32_t>>
+      m_udt_declarations;
+  bool m_has_cached_udt_declatations = false;
+
   lldb_private::UniqueCStringMap<uint32_t> m_type_base_names;
 };
 
diff --git a/lldb/test/Shell/SymbolFile/PDB/class-layout.test b/lldb/test/Shell/SymbolFile/PDB/class-layout.test
index e9a7d1c0daa9e..eca910e997e40 100644
--- a/lldb/test/Shell/SymbolFile/PDB/class-layout.test
+++ b/lldb/test/Shell/SymbolFile/PDB/class-layout.test
@@ -12,9 +12,19 @@ RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix
 RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=BASE %s
 RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=FRIEND %s
 RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=CLASS %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=UNION %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=STRUCT %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=COMPLEX %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=LIST %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=UNNAMED-STRUCT %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=BASE %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=FRIEND %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=CLASS %s
 
 CHECK: Module [[MOD:.*]]
-CHECK: SymbolFile pdb ([[MOD]])
+CHECK: SymbolFile {{(native-)?}}pdb ([[MOD]])
 CHECK: {{^[0-9A-F]+}}:   CompileUnit{{[{]0x[0-9a-f]+[}]}}, language = "c++", file = '{{.*}}\ClassLayoutTest.cpp'
 
 ENUM:  name = "Enum", size = 4,  decl = ClassLayoutTest.cpp:5
diff --git a/lldb/test/Shell/SymbolFile/PDB/enums-layout.test b/lldb/test/Shell/SymbolFile/PDB/enums-layout.test
index 6f861c6d65adf..9766d6f8b0324 100644
--- a/lldb/test/Shell/SymbolFile/PDB/enums-layout.test
+++ b/lldb/test/Shell/SymbolFile/PDB/enums-layout.test
@@ -7,6 +7,12 @@ RUN: lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-
 RUN: lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=UCHAR-ENUM %s
 RUN: lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=CLASS-ENUM %s
 RUN: lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=STRUCT-ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=CONST-ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=EMPTY-ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=UCHAR-ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=CLASS-ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=STRUCT-ENUM %s
 
 ; FIXME: PDB does not have information about scoped enumeration (Enum class) so the  
 ; compiler type used is the same as the one for unscoped enumeration.

Michael137 · 2025-08-12T06:37:37Z

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

@@ -12,9 +12,19 @@ RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix
 RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=BASE %s
 RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=FRIEND %s
 RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=CLASS %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck %s


I find it a bit awkward that we have NativePDB tests running outside of the SymbolFile/NativePDB test directory. Can we just put this test into the NativePDB directory too?

Forgot to reply to this...

My concern was that this would now duplicate the test input and the expected output. We do the mixed tests in Shell/SymbolFile/PDB a few times.

Hmmm ok, lets just make sure we don't lose this coverage when we remove the DIA PDB plugin

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp

Michael137 · 2025-08-12T06:46:38Z

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp

+  // rustc sets the filename to "<unknown>" for some files
+  if (*file_name == "\\<unknown>")
+    return Declaration();


Is there a way to test this?

Good call, I added a test, noticed that LLVM emits the information as LF_UDT_SRC_LINE and handled that as well. We tested with clang-cl + MSVC link before.
I think MSVC's linker rewrites LF_UDT_SRC_LINE to LF_UDT_MOD_SRC_LINE to save space, but I haven't verified that. Either way, we need to handle both.

Michael137 · 2025-08-12T06:48:23Z

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp

+  FileSpec::Style style = file_name->starts_with("/")
+                              ? FileSpec::Style::posix
+                              : FileSpec::Style::windows;


What's the file_name in this context? When would it start with a / or \?

When I compiled Rust code, filenames from the standard library in the string table showed up as

5631 | '/rustc/430d6eddfc6a455ca4a0137c0822a982cccd3b2b/library\core\src\ptr\mod.rs' 5707 | '/rustc/430d6eddfc6a455ca4a0137c0822a982cccd3b2b/library\core\src\mem\mod.rs' ...

I just noticed the backslashes which can't occur on posix - so these are probably paths relative to C:\.

ZequanWu

LGTM

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.h

Co-authored-by: Michael Buch <[email protected]>

Michael137 · 2025-08-13T13:49:44Z

@Nerixyz I suggest you request commit access. Can be done here: https://llvm.org/docs/DeveloperPolicy.html#obtaining-commit-access

That way you can merge your own PRs in the future

kazutakahirata · 2025-08-13T16:26:40Z

@Nerixyz I've landed bfc331e to fix warnings from this PR. Thanks!

Nerixyz · 2025-08-13T16:53:07Z

@Nerixyz I've landed bfc331e to fix warnings from this PR. Thanks!

Thank you!

Nerixyz requested a review from JDevlieghere as a code owner August 7, 2025 19:12

llvmbot added the lldb label Aug 7, 2025

JDevlieghere requested review from ZequanWu, Michael137 and omjavaid August 12, 2025 01:50

Michael137 reviewed Aug 12, 2025

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ZequanWu approved these changes Aug 12, 2025

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Michael137 reviewed Aug 13, 2025

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Nerixyz and others added 7 commits August 13, 2025 11:09

[LLDB][NativePDB] Resolve declaration for tag types

2f4c134

fix: use std::once_flag

e7c51c5

fix: use llvm::Expected

4066478

feat: handle LF_UDT_SRC_LINE as well

2f0c1dc

test: add test for rustc's <unknown>

4391dd6

fix: use native path style

934f575

Apply suggestions from code review

bd4bb25

Co-authored-by: Michael Buch <[email protected]>

Nerixyz force-pushed the feat/lldb-npdb-udt-decl branch from 0c2607d to bd4bb25 Compare August 13, 2025 09:09

Michael137 merged commit 3f61e4e into llvm:main Aug 13, 2025
9 checks passed

Nerixyz deleted the feat/lldb-npdb-udt-decl branch August 13, 2025 13:59

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[LLDB][NativePDB] Resolve declaration for tag types #152579

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