[DebugLine] Improve path handling.

[JDevlieghere]

Summary

After switching over LLDB's line table parser to libDebugInfo, we noticed two regressions on the Windows bot. The problem is that when obtaining a file from the line table prologue, we append paths without specifying a path style. This leads to incorrect results on Windows for debug info containing Posix paths:

0x0000000000201000: /tmp\b.c, is_start_of_statement = TRUE

This patch is an attempt to fix that by guessing the path style whenever possible.

[JDevlieghere]

This should fix the following two test failures on the Windows LLDB bot (http://lab.llvm.org:8011/builders/lldb-x64-windows-ninja)

LLDB :: SymbolFile/DWARF/debug-line-basic.s
LLDB :: SymbolFile/DWARF/dir-separator-posix.s

Unfortunately I don't have access to a Windows machine, so I'm not able to verify this.

[aprantl]

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

183 ↗

(On Diff #215142)

you can just use llvm::Optional::getValueOr(FileSpec::Style::native) instead of this function.

[aprantl]

LGTM with some minor details addressed, thanks!

llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

1044 ↗

(On Diff #215142)

/// If this is an absolute path, detect ...

lldb/trunk/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

ParseLLVMLineTable(lldb_private::DWARFContext &context,
   if (!line_table) {
     LLDB_LOG_ERROR(log, line_table.takeError(),
                    "SymbolFileDWARF::ParseLineTable failed to parse");
     return nullptr;
   }
   return *line_table;
 }
 
+static FileSpec::Style GuessPathStyleOrNative(llvm::StringRef p) {
+  llvm::Optional<FileSpec::Style> style = FileSpec::GuessPathStyle(p);
+  return style ? *style : FileSpec::Style::native;
+}
+
 static FileSpecList
 ParseSupportFilesFromPrologue(const lldb::ModuleSP &module,
                               const llvm::DWARFDebugLine::Prologue &prologue,
                               llvm::StringRef compile_dir = {},
                               FileSpec first_file = {}) {
   FileSpecList support_files;
   support_files.Append(first_file);
 
-  llvm::Optional<FileSpec::Style> compile_dir_style =
-      FileSpec::GuessPathStyle(compile_dir);
   const size_t number_of_files = prologue.FileNames.size();
   for (size_t idx = 1; idx <= number_of_files; ++idx) {
     std::string original_file;
     if (!prologue.getFileNameByIndex(
             idx, compile_dir,
             llvm::DILineInfoSpecifier::FileLineInfoKind::Default,
             original_file)) {
       // Always add an entry so the indexes remain correct.
       support_files.EmplaceBack();
       continue;
     }
 
-    FileSpec::Style style = FileSpec::Style::native;
-    if (compile_dir_style) {
-      style = *compile_dir_style;
-    } else if (llvm::Optional<FileSpec::Style> file_style =
-                   FileSpec::GuessPathStyle(original_file)) {
-      style = *file_style;
-    }
-
     std::string remapped_file;
     if (!prologue.getFileNameByIndex(
             idx, compile_dir,
             llvm::DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath,
             remapped_file)) {
       // Always add an entry so the indexes remain correct.
-      support_files.EmplaceBack(original_file, style);
+      support_files.EmplaceBack(original_file,
+                                FileSpec::GuessPathStyle(original_file)
+                                    .getValueOr(FileSpec::Style::native));
       continue;
     }
 
     module->RemapSourceFile(llvm::StringRef(original_file), remapped_file);
-    support_files.EmplaceBack(remapped_file, style);
+    support_files.EmplaceBack(remapped_file,
+                              FileSpec::GuessPathStyle(remapped_file)
+                                  .getValueOr(FileSpec::Style::native));
   }
 
   return support_files;
 }
 
 FileSpecList SymbolFileDWARF::GetSymlinkPaths() {
   return GetGlobalPluginProperties()->GetSymLinkPaths();
 }

llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

 static bool isPathAbsoluteOnWindowsOrPosix(const Twine &Path) {
   // Debug info can contain paths from any OS, not necessarily
   // an OS we're currently running on. Moreover different compilation units can
   // be compiled on different operating systems and linked together later.
   return sys::path::is_absolute(Path, sys::path::Style::posix) ||
          sys::path::is_absolute(Path, sys::path::Style::windows);
 }
 
+/// If given an absolute path, guess the path style.
+static sys::path::Style GuessPathStyle(StringRef Path) {
+  bool Posix = sys::path::is_absolute(Path, sys::path::Style::posix);
+  bool Windows = sys::path::is_absolute(Path, sys::path::Style::windows);
+  // This is a relative path.
+  if (!Posix && !Windows)
+    return sys::path::Style::native;
+  // This is a valid absolute path for both Windows and Posix.
+  if (Posix && Windows)
+    return sys::path::Style::native;
+  if (Posix)
+    return sys::path::Style::posix;
+  if (Windows)
+    return sys::path::Style::windows;
+
+  llvm_unreachable("All combinations should have been handled.");
+}
+
 bool DWARFDebugLine::Prologue::getFileNameByIndex(uint64_t FileIndex,
                                                   StringRef CompDir,
                                                   FileLineInfoKind Kind,
                                                   std::string &Result) const {
   if (Kind == FileLineInfoKind::None || !hasFileAtIndex(FileIndex))
     return false;
   const FileNameEntry &Entry = getFileNameEntry(FileIndex);
   StringRef FileName = Entry.Name.getAsCString().getValue();
if (getVersion() >= 5) {
     if (0 < Entry.DirIdx && Entry.DirIdx <= IncludeDirectories.size())
       IncludeDir =
           IncludeDirectories[Entry.DirIdx - 1].getAsCString().getValue();
 
     // We may still need to append compilation directory of compile unit.
     // We know that FileName is not absolute, the only way to have an
     // absolute path at this point would be if IncludeDir is absolute.
     if (!CompDir.empty() && !isPathAbsoluteOnWindowsOrPosix(IncludeDir))
-      sys::path::append(FilePath, CompDir);
+      sys::path::append(FilePath, GuessPathStyle(CompDir), CompDir);
   }
 
   // sys::path::append skips empty strings.
-  sys::path::append(FilePath, IncludeDir, FileName);
+  sys::path::append(FilePath, GuessPathStyle(IncludeDir), IncludeDir, FileName);
   Result = FilePath.str();
   return true;
 }
 
 bool DWARFDebugLine::LineTable::getFileLineInfoForAddress(
     object::SectionedAddress Address, const char *CompDir,
     FileLineInfoKind Kind, DILineInfo &Result) const {
   // Get the index of row we're looking for in the line table.