[PDB] Add PDBSourcePath flag to support absolutize source file path

[takuto.ikuta]

Summary

This patch changes relative path for source files in obj files to absolute path in PDB when linking with added flag.

I will make obj file generated by clang-cl independent from build directory for chromium build. But I don't want to confuse visual studio debugger or require additional configuration. To attain this goal, I added flag to convert relative source file path in obj to absolute path when emitting PDB.

By removing absolute path from obj files, we can share build cache between chromium developers even when they are doing debug build.
That will make build time faster.

More context:
https://bugs.chromium.org/p/chromium/issues/detail?id=712796
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/5HXSVX-7fPc

[zturner]

lld/COFF/PDB.cpp

935–944

I don't think it's correct to force Windows path style here. I think we should just use the default native style.

If you are doing a cross-compilation, then the code here will emit a path into the object file that doesn't make any sense or correspond to the actual machine that the file was generated on, which seems wrong.

This doesn't matter too much for MSVC since you will never run it on Linux anyway, but one could imagine that someday some other debugger (LLDB, GDB, etc) will be taught how to natively parse PDB files, and maybe on Linux it would be able to debug code running under WINE while the debug info and sources are on a native Linux partition. So it doesn't seem correct to lock PDBs to a Windows host at the file format level.

[takuto.ikuta]

Use native path style

[takuto.ikuta]

lld/COFF/PDB.cpp

935–944

I see. But I just tried to follow the code in L814.

[thakis]

Thanks for the patch! I wonder if this should be behind some flag (/makePDBPathsAbsolute or something) and not be done by default. If we have a flag, the flag could also optionally provide a different prefix than pwd (/makePDBPathsAbsolute:c:\src), which might be useful for cross builds. I'd like to hear ruiu's thoughts on this.

This shouldn't have a measurable impact on link time, right?

[takuto.ikuta]

Use given path to normalize path

[takuto.ikuta]

Thank you for taking a look.

In D48882#1154227, @thakis wrote:

Thanks for the patch! I wonder if this should be behind some flag (/makePDBPathsAbsolute or something) and not be done by default. If we have a flag, the flag could also optionally provide a different prefix than pwd (/makePDBPathsAbsolute:c:\src), which might be useful for cross builds. I'd like to hear ruiu's thoughts on this.

It makes sense to me. Added a flag.

This shouldn't have a measurable impact on link time, right?

I confirmed this does not show visible performance difference.

[takuto.ikuta]

Ping? Can I go this way?

[takuto.ikuta]

If some of you have concern about this, please leave a comment.

I'll ask commit right and merge this if I could be a committer.

[thakis]

Looks good to me, thanks!

[ruiu]

lld/COFF/Config.h

105–108

Sort.

lld/COFF/PDB.cpp

935–944

If we should use the native pathname rather than Windows one, then you probably should do either is_absolute(Filename, Sytle::windows) or is_absolute(Filename, Style::posix) but not both, since X:/foo is a relative path on Unix.

lld/test/COFF/pdb-relative-source-lines.test

49

Don't you need only the lines that contain pathname? I'd remove all the other lines from the file, so that we don't have to update them when some unrelated change is committed.

[takuto.ikuta]

Shrink test data

[takuto.ikuta]

lld/test/COFF/pdb-relative-source-lines.test

49

Shrinked, but let me keep hardly be changed lines as anchor.

[ruiu]

lld/COFF/Options.td

144

Help text shouldn't end with a period. Please always look around and follow the local convention. That's I think important.

Is this considered an internal option, or this is intended to be used directly by users? If it is intended to be used widely, the option name "/makepdbpathabsolute" seems a bit weird to me. There's no existing option name like that. Perhaps something like "/pdbpath:absolute" is better.

[takuto.ikuta]

pdbsourcepath

[takuto.ikuta]

lld/COFF/Options.td

144

Basically, I don't expect this option will be used by user widely, because this option has no meaning for obj files without clang-cl's internal -fdebug-compilation-dir option.

But path normalization feature will be useful for debuggable executable from reproducible obj files. And some other users may use this. So I changed the flag name.

[ruiu]

Is Ukai-san OK with this change?

lld/COFF/Options.td

143–144

Other options seems to be sorted, so please sort alphabetically. It is nitpicky but consistency matters, so please spend a bit more time to read code around the location you are changing so that your new code doesn't look too different. I think that's important and actually saves both your and my time.

[takuto.ikuta]

sort

[takuto.ikuta]

In D48882#1161855, @ruiu wrote:

Is Ukai-san OK with this change?

Yes, I got agreement on this way from him.

[takuto.ikuta]

Landed as
https://reviews.llvm.org/rLLD337439

lld/COFF/Config.h

struct Configuration {
   bool Force = false;
   bool Debug = false;
   bool DebugDwarf = false;
   bool DebugGHashes = false;
   bool DebugSymtab = false;
   bool ShowTiming = false;
   unsigned DebugTypes = static_cast<unsigned>(DebugType::None);
   std::vector<std::string> NatvisFiles;
   llvm::SmallString<128> PDBAltPath;
   llvm::SmallString<128> PDBPath;
+  llvm::SmallString<128> PDBSourcePath;
   std::vector<llvm::StringRef> Argv;
 
   // Symbols in this set are considered as live by the garbage collector.
   std::vector<Symbol *> GCRoot;
 
   std::set<StringRef> NoDefaultLibs;
   bool NoDefaultLibAll = false;
 
   // True if we are creating a DLL.

lld/COFF/Driver.cpp

void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
   bool ShouldCreatePDB = Args.hasArg(OPT_debug, OPT_debug_ghash);
   if (ShouldCreatePDB) {
     if (auto *Arg = Args.getLastArg(OPT_pdb))
       Config->PDBPath = Arg->getValue();
     if (auto *Arg = Args.getLastArg(OPT_pdbaltpath))
       Config->PDBAltPath = Arg->getValue();
     if (Args.hasArg(OPT_natvis))
       Config->NatvisFiles = Args.getAllArgValues(OPT_natvis);
+
+    if (auto *Arg = Args.getLastArg(OPT_pdb_source_path))
+      Config->PDBSourcePath = Arg->getValue();
   }
 
   // Handle /noentry
   if (Args.hasArg(OPT_noentry)) {
     if (Args.hasArg(OPT_dll))
       Config->NoEntry = true;
     else
       error("/noentry must be specified with /dll");

lld/COFF/Options.td

 
 def help : F<"help">;
 def help_q : Flag<["/?", "-?"], "">, Alias<help>;
 
 // LLD extensions
 def debug_ghash : F<"debug:ghash">;
 def debug_dwarf : F<"debug:dwarf">;
 def debug_symtab : F<"debug:symtab">;
 def export_all_symbols : F<"export-all-symbols">;
 def kill_at : F<"kill-at">;
 def lldmingw : F<"lldmingw">;
 def msvclto : F<"msvclto">;
 def output_def : Joined<["/", "-"], "output-def:">;
+def pdb_source_path : P<"pdbsourcepath",
+                        "Base path used to make relative source file path absolute in PDB">;
 def rsp_quoting : Joined<["--"], "rsp-quoting=">,
   HelpText<"Quoting style for response files, 'windows' (default) or 'posix'">;
 def dash_dash_version : Flag<["--"], "version">,
   HelpText<"Print version information">;
 
 // Flags for debugging
 def lldmap : F<"lldmap">;
 def lldmap_file : Joined<["/", "-"], "lldmap:">;

lld/COFF/PDB.cpp

void PDBLinker::addObjFile(ObjFile *File) {
   }
 
   // Make a new file checksum table that refers to offsets in the PDB-wide
   // string table. Generally the string table subsection appears after the
   // checksum table, so we have to do this after looping over all the
   // subsections.
   auto NewChecksums = make_unique<DebugChecksumsSubsection>(PDBStrTab);
   for (FileChecksumEntry &FC : Checksums) {
-    StringRef FileName = ExitOnErr(CVStrTab.getString(FC.FileNameOffset));
+    SmallString<128> FileName = ExitOnErr(CVStrTab.getString(FC.FileNameOffset));
+    if (!sys::path::is_absolute(FileName) &&
+        !Config->PDBSourcePath.empty()) {
+      SmallString<128> AbsoluteFileName = Config->PDBSourcePath;
+      sys::path::append(AbsoluteFileName, FileName);
+      sys::path::native(AbsoluteFileName);
+      sys::path::remove_dots(AbsoluteFileName, /*remove_dot_dots=*/true);
+      FileName = std::move(AbsoluteFileName);
+    }
     ExitOnErr(Builder.getDbiBuilder().addModuleSourceFile(*File->ModuleDBI,
                                                           FileName));
     NewChecksums->addChecksum(FileName, FC.Kind, FC.Checksum);
   }
   File->ModuleDBI->addDebugSubsection(std::move(NewChecksums));
 }
 
 static PublicSym32 createPublic(Defined *Def) {
   PublicSym32 Pub(SymbolKind::S_PUB32);

lld/test/COFF/Inputs/pdb_lines_1_relative.yaml

+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+  Characteristics: [  ]
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       16
+    SectionData:     4883EC28C744242400000000E800000000B82A0000004883C428C3
+    Relocations:
+      - VirtualAddress:  13
+        SymbolName:      foo
+        Type:            IMAGE_REL_AMD64_REL32
+  - Name:            .data
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       4
+    SectionData:     ''
+  - Name:            .bss
+    Characteristics: [ IMAGE_SCN_CNT_UNINITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       4
+    SectionData:     ''
+  - Name:            .xdata
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     '0104010004420000'
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       16
+    SectionData:     4883EC28E800000000904883C428C3
+    Relocations:
+      - VirtualAddress:  5
+        SymbolName:      bar
+        Type:            IMAGE_REL_AMD64_REL32
+  - Name:            .drectve
+    Characteristics: [ IMAGE_SCN_LNK_INFO, IMAGE_SCN_LNK_REMOVE ]
+    Alignment:       1
+    SectionData:     202F44454641554C544C49423A6C6962636D742E6C6962202F44454641554C544C49423A6F6C646E616D65732E6C6962
+  - Name:            '.debug$S'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData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
+    Subsections:
+      - !Symbols
+        Records:
+          - Kind:            S_COMPILE3
+            Compile3Sym:
+              Flags:           [  ]
+              Machine:         X64
+              FrontendMajor:   7
+              FrontendMinor:   0
+              FrontendBuild:   0
+              FrontendQFE:     0
+              BackendMajor:    7000
+              BackendMinor:    0
+              BackendBuild:    0
+              BackendQFE:      0
+              Version:         'clang version 7.0.0 '
+      - !Symbols
+        Records:
+          - Kind:            S_GPROC32_ID
+            ProcSym:
+              CodeSize:        27
+              DbgStart:        0
+              DbgEnd:          0
+              FunctionType:    4098
+              Flags:           [  ]
+              DisplayName:     main
+          - Kind:            S_PROC_ID_END
+            ScopeEndSym:
+      - !Lines
+        CodeSize:        27
+        Flags:           [  ]
+        RelocOffset:     0
+        RelocSegment:    0
+        Blocks:
+          - FileName:        '.\pdb_lines_1.c'
+            Lines:
+              - Offset:          0
+                LineStart:       2
+                IsStatement:     false
+                EndDelta:        0
+              - Offset:          12
+                LineStart:       3
+                IsStatement:     false
+                EndDelta:        0
+              - Offset:          17
+                LineStart:       4
+                IsStatement:     false
+                EndDelta:        0
+            Columns:
+      - !FileChecksums
+        Checksums:
+          - FileName:        '.\pdb_lines_1.c'
+            Kind:            MD5
+            Checksum:        EA6429BCE282CCF3F0E3CD93B216EB41
+          - FileName:        '.\foo.h'
+            Kind:            MD5
+            Checksum:        061EB73ABB642532857A4F1D9CBAC323
+      - !StringTable
+        Strings:
+          - '.\pdb_lines_1.c'
+          - '.\foo.h'
+          - ''
+          - ''
+          - ''
+    Relocations:
+      - VirtualAddress:  100
+        SymbolName:      main
+        Type:            IMAGE_REL_AMD64_SECREL
+      - VirtualAddress:  104
+        SymbolName:      main
+        Type:            IMAGE_REL_AMD64_SECTION
+      - VirtualAddress:  124
+        SymbolName:      main
+        Type:            IMAGE_REL_AMD64_SECREL
+      - VirtualAddress:  128
+        SymbolName:      main
+        Type:            IMAGE_REL_AMD64_SECTION
+  - Name:            '.debug$T'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     0400000006000112000000000E0008107400000000000000001000001200011600000000011000006D61696E00F3F2F10E0008100300000000000000001000000E0001160000000003100000666F6F00
+    Types:
+      - Kind:            LF_ARGLIST
+        ArgList:
+          ArgIndices:      [  ]
+      - Kind:            LF_PROCEDURE
+        Procedure:
+          ReturnType:      116
+          CallConv:        NearC
+          Options:         [ None ]
+          ParameterCount:  0
+          ArgumentList:    4096
+      - Kind:            LF_FUNC_ID
+        FuncId:
+          ParentScope:     0
+          FunctionType:    4097
+          Name:            main
+      - Kind:            LF_PROCEDURE
+        Procedure:
+          ReturnType:      3
+          CallConv:        NearC
+          Options:         [ None ]
+          ParameterCount:  0
+          ArgumentList:    4096
+      - Kind:            LF_FUNC_ID
+        FuncId:
+          ParentScope:     0
+          FunctionType:    4099
+          Name:            foo
+  - Name:            .pdata
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     000000001B00000000000000
+    Relocations:
+      - VirtualAddress:  0
+        SymbolName:      main
+        Type:            IMAGE_REL_AMD64_ADDR32NB
+      - VirtualAddress:  4
+        SymbolName:      main
+        Type:            IMAGE_REL_AMD64_ADDR32NB
+      - VirtualAddress:  8
+        SymbolName:      .xdata
+        Type:            IMAGE_REL_AMD64_ADDR32NB
+  - Name:            .xdata
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     '0104010004420000'
+  - Name:            '.debug$S'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     04000000F10000002F000000290047110000000000000000000000000F00000000000000000000000410000000000000000000666F6F0002004F1100F20000003000000000000000000000000F000000180000000300000024000000000000000200000004000000030000000900000004000000
+    Subsections:
+      - !Symbols
+        Records:
+          - Kind:            S_GPROC32_ID
+            ProcSym:
+              CodeSize:        15
+              DbgStart:        0
+              DbgEnd:          0
+              FunctionType:    4100
+              Flags:           [  ]
+              DisplayName:     foo
+          - Kind:            S_PROC_ID_END
+            ScopeEndSym:
+      - !Lines
+        CodeSize:        15
+        Flags:           [  ]
+        RelocOffset:     0
+        RelocSegment:    0
+        Blocks:
+          - FileName:        '.\foo.h'
+            Lines:
+              - Offset:          0
+                LineStart:       2
+                IsStatement:     false
+                EndDelta:        0
+              - Offset:          4
+                LineStart:       3
+                IsStatement:     false
+                EndDelta:        0
+              - Offset:          9
+                LineStart:       4
+                IsStatement:     false
+                EndDelta:        0
+            Columns:
+    Relocations:
+      - VirtualAddress:  44
+        SymbolName:      foo
+        Type:            IMAGE_REL_AMD64_SECREL
+      - VirtualAddress:  48
+        SymbolName:      foo
+        Type:            IMAGE_REL_AMD64_SECTION
+      - VirtualAddress:  68
+        SymbolName:      foo
+        Type:            IMAGE_REL_AMD64_SECREL
+      - VirtualAddress:  72
+        SymbolName:      foo
+        Type:            IMAGE_REL_AMD64_SECTION
+  - Name:            .pdata
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     000000000F00000000000000
+    Relocations:
+      - VirtualAddress:  0
+        SymbolName:      foo
+        Type:            IMAGE_REL_AMD64_ADDR32NB
+      - VirtualAddress:  4
+        SymbolName:      foo
+        Type:            IMAGE_REL_AMD64_ADDR32NB
+      - VirtualAddress:  8
+        SymbolName:      .xdata
+        Type:            IMAGE_REL_AMD64_ADDR32NB
+symbols:
+  - Name:            .text
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          27
+      NumberOfRelocations: 1
+      NumberOfLinenumbers: 0
+      CheckSum:        3051916600
+      Number:          1
+  - Name:            .data
+    Value:           0
+    SectionNumber:   2
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          0
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          2
+  - Name:            .bss
+    Value:           0
+    SectionNumber:   3
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          0
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          3
+  - Name:            .xdata
+    Value:           0
+    SectionNumber:   4
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          8
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        264583633
+      Number:          4
+  - Name:            .text
+    Value:           0
+    SectionNumber:   5
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          15
+      NumberOfRelocations: 1
+      NumberOfLinenumbers: 0
+      CheckSum:        236440503
+      Number:          5
+      Selection:       IMAGE_COMDAT_SELECT_ANY
+  - Name:            foo
+    Value:           0
+    SectionNumber:   5
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            .xdata
+    Value:           0
+    SectionNumber:   10
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          8
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        264583633
+      Number:          5
+      Selection:       IMAGE_COMDAT_SELECT_ASSOCIATIVE
+  - Name:            .drectve
+    Value:           0
+    SectionNumber:   6
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          48
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        149686238
+      Number:          6
+  - Name:            '.debug$S'
+    Value:           0
+    SectionNumber:   7
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          264
+      NumberOfRelocations: 4
+      NumberOfLinenumbers: 0
+      CheckSum:        2204933783
+      Number:          7
+  - Name:            '.debug$S'
+    Value:           0
+    SectionNumber:   11
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          116
+      NumberOfRelocations: 4
+      NumberOfLinenumbers: 0
+      CheckSum:        2691661839
+      Number:          5
+      Selection:       IMAGE_COMDAT_SELECT_ASSOCIATIVE
+  - Name:            '.debug$T'
+    Value:           0
+    SectionNumber:   8
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          80
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        3541780432
+      Number:          8
+  - Name:            .pdata
+    Value:           0
+    SectionNumber:   9
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          12
+      NumberOfRelocations: 3
+      NumberOfLinenumbers: 0
+      CheckSum:        567356797
+      Number:          9
+  - Name:            .pdata
+    Value:           0
+    SectionNumber:   12
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          12
+      NumberOfRelocations: 3
+      NumberOfLinenumbers: 0
+      CheckSum:        3642757804
+      Number:          5
+      Selection:       IMAGE_COMDAT_SELECT_ASSOCIATIVE
+  - Name:            main
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            bar
+    Value:           0
+    SectionNumber:   0
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...

lld/test/COFF/Inputs/pdb_lines_2_relative.yaml

+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+  Characteristics: [  ]
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       16
+    SectionData:     C3
+  - Name:            .data
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       4
+    SectionData:     ''
+  - Name:            .bss
+    Characteristics: [ IMAGE_SCN_CNT_UNINITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       4
+    SectionData:     ''
+  - Name:            .drectve
+    Characteristics: [ IMAGE_SCN_LNK_INFO, IMAGE_SCN_LNK_REMOVE ]
+    Alignment:       1
+    SectionData:     202F44454641554C544C49423A6C6962636D742E6C6962202F44454641554C544C49423A6F6C646E616D65732E6C6962
+  - Name:            '.debug$S'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     04000000F10000002F0000002D003C1100000000D0000700000000000000581B000000000000636C616E672076657273696F6E20372E302E30200000F10000002F0000002900471100000000000000000000000001000000000000000000000002100000000000000000006261720002004F1100F2000000200000000000000000000000010000000000000001000000140000000000000002000000F400000018000000010000001001DF91CB3A2B8D917486574BB50CAC4CC70000F300000014000000002E5C7064625F6C696E65735F322E6300000000
+    Subsections:
+      - !Symbols
+        Records:
+          - Kind:            S_COMPILE3
+            Compile3Sym:
+              Flags:           [  ]
+              Machine:         X64
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+              FrontendMinor:   0
+              FrontendBuild:   0
+              FrontendQFE:     0
+              BackendMajor:    7000
+              BackendMinor:    0
+              BackendBuild:    0
+              BackendQFE:      0
+              Version:         'clang version 7.0.0 '
+      - !Symbols
+        Records:
+          - Kind:            S_GPROC32_ID
+            ProcSym:
+              CodeSize:        1
+              DbgStart:        0
+              DbgEnd:          0
+              FunctionType:    4098
+              Flags:           [  ]
+              DisplayName:     bar
+          - Kind:            S_PROC_ID_END
+            ScopeEndSym:
+      - !Lines
+        CodeSize:        1
+        Flags:           [  ]
+        RelocOffset:     0
+        RelocSegment:    0
+        Blocks:
+          - FileName:        '.\pdb_lines_2.c'
+            Lines:
+              - Offset:          0
+                LineStart:       2
+                IsStatement:     false
+                EndDelta:        0
+            Columns:
+      - !FileChecksums
+        Checksums:
+          - FileName:        '.\pdb_lines_2.c'
+            Kind:            MD5
+            Checksum:        DF91CB3A2B8D917486574BB50CAC4CC7
+      - !StringTable
+        Strings:
+          - '.\pdb_lines_2.c'
+          - ''
+          - ''
+          - ''
+    Relocations:
+      - VirtualAddress:  100
+        SymbolName:      bar
+        Type:            IMAGE_REL_AMD64_SECREL
+      - VirtualAddress:  104
+        SymbolName:      bar
+        Type:            IMAGE_REL_AMD64_SECTION
+      - VirtualAddress:  124
+        SymbolName:      bar
+        Type:            IMAGE_REL_AMD64_SECREL
+      - VirtualAddress:  128
+        SymbolName:      bar
+        Type:            IMAGE_REL_AMD64_SECTION
+  - Name:            '.debug$T'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     0400000006000112000000000E0008100300000000000000001000000E000116000000000110000062617200
+    Types:
+      - Kind:            LF_ARGLIST
+        ArgList:
+          ArgIndices:      [  ]
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+        Procedure:
+          ReturnType:      3
+          CallConv:        NearC
+          Options:         [ None ]
+          ParameterCount:  0
+          ArgumentList:    4096
+      - Kind:            LF_FUNC_ID
+        FuncId:
+          ParentScope:     0
+          FunctionType:    4097
+          Name:            bar
+symbols:
+  - Name:            .text
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          1
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        40735498
+      Number:          1
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+    Value:           0
+    SectionNumber:   2
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
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+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
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+    SectionNumber:   3
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          0
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          3
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+    Value:           0
+    SectionNumber:   4
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          48
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
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+      Number:          4
+  - Name:            '.debug$S'
+    Value:           0
+    SectionNumber:   5
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          216
+      NumberOfRelocations: 4
+      NumberOfLinenumbers: 0
+      CheckSum:        2383431754
+      Number:          5
+  - Name:            '.debug$T'
+    Value:           0
+    SectionNumber:   6
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          44
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        179171995
+      Number:          6
+  - Name:            bar
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...

lld/test/COFF/pdb-relative-source-lines.test

+Test the linker line tables on roughly the following example:
+
+==> foo.h <==
+void bar(void);
+inline void foo(void) {
+  bar();
+}
+==> pdb_lines_1.c <==
+#include "foo.h"
+int main(void) {
+  foo();
+  return 42;
+}
+==> pdb_lines_2.c <==
+void bar(void) {
+}
+
+$ clang-cl -Xclang -fdebug-compilation-dir -Xclang . -c -Z7 pdb_lines*.c
+
+RUN: yaml2obj %S/Inputs/pdb_lines_1_relative.yaml -o %t.pdb_lines_1_relative.obj
+RUN: yaml2obj %S/Inputs/pdb_lines_2_relative.yaml -o %t.pdb_lines_2_relative.obj
+RUN: rm -f %t.exe %t.pdb
+RUN: lld-link -debug -pdbsourcepath:c:\\src -entry:main -nodefaultlib -out:%t.exe -pdb:%t.pdb %t.pdb_lines_1_relative.obj %t.pdb_lines_2_relative.obj
+RUN: llvm-pdbutil pdb2yaml -modules -module-files -subsections=lines,fc %t.pdb | FileCheck %s
+
+CHECK-LABEL:  - Module:          {{.*}}pdb_lines_1_relative.obj
+CHECK-NEXT:     ObjFile:         {{.*}}pdb_lines_1_relative.obj
+CHECK:          SourceFiles:
+CHECK-NEXT:       - 'c:{{[\\/]}}src{{[\\/]}}pdb_lines_1.c'
+CHECK-NEXT:       - 'c:{{[\\/]}}src{{[\\/]}}foo.h'
+CHECK:          Subsections:
+CHECK:                - FileName:        'c:{{[\\/]}}src{{[\\/]}}pdb_lines_1.c'
+CHECK:                - FileName:        'c:{{[\\/]}}src{{[\\/]}}foo.h'
+CHECK:            - !FileChecksums
+CHECK:                - FileName:        'c:{{[\\/]}}src{{[\\/]}}pdb_lines_1.c'
+CHECK:                - FileName:        'c:{{[\\/]}}src{{[\\/]}}foo.h'
+
+CHECK-LABEL:  - Module:          {{.*}}pdb_lines_2_relative.obj
+CHECK-NEXT:     ObjFile:         {{.*}}pdb_lines_2_relative.obj
+CHECK:          SourceFiles:
+CHECK-NEXT:       - 'c:{{[\\/]}}src{{[\\/]}}pdb_lines_2.c'
+CHECK:          Subsections:
+CHECK:                - FileName:        'c:{{[\\/]}}src{{[\\/]}}pdb_lines_2.c'
+CHECK:            - !FileChecksums
+CHECK:                - FileName:        'c:{{[\\/]}}src{{[\\/]}}pdb_lines_2.c'