Index: include/lldb/Utility/FileSpec.h
===================================================================
--- include/lldb/Utility/FileSpec.h
+++ include/lldb/Utility/FileSpec.h
@@ -242,6 +242,13 @@
 
   static bool Equal(const FileSpec &a, const FileSpec &b, bool full);
 
+  /// Attempt to guess path style for a given path string. It returns a style,
+  /// if it was able to make a reasonable guess, or None if it wasn't. The guess
+  /// will be correct if the input path was a valid absolute path on the system
+  /// which produced it. On other paths the result of this function is
+  /// unreliable (e.g. "c:\foo.txt" is a valid relative posix path).
+  static llvm::Optional<Style> GuessPathStyle(llvm::StringRef absolute_path);
+
   //------------------------------------------------------------------
   /// Case sensitivity of path.
   ///
Index: lit/SymbolFile/Breakpad/Inputs/line-table-mixed-path-styles.syms
===================================================================
--- /dev/null
+++ lit/SymbolFile/Breakpad/Inputs/line-table-mixed-path-styles.syms
@@ -0,0 +1,7 @@
+MODULE Linux x86_64 761550E08086333960A9074A9CE2895C0 a.out
+INFO CODE_ID E05015768680393360A9074A9CE2895C
+FILE 0 /tmp/a.c
+FILE 1 c:\tmp\b.c
+FUNC b0 10 0 func
+b0 1 1 0
+b1 1 1 1
Index: lit/SymbolFile/Breakpad/line-table-discontinuous-file-ids.test
===================================================================
--- lit/SymbolFile/Breakpad/line-table-discontinuous-file-ids.test
+++ lit/SymbolFile/Breakpad/line-table-discontinuous-file-ids.test
@@ -1,7 +1,5 @@
 # Test that we handle files which has gaps in the FILE record IDs.
 
-# XFAIL: system-windows
-
 # RUN: yaml2obj %S/Inputs/basic-elf.yaml > %T/line-table-discontinuous-file-ids.out
 # RUN: %lldb %T/line-table-discontinuous-file-ids.out \
 # RUN:   -o "target symbols add -s line-table-discontinuous-file-ids.out %S/Inputs/line-table-discontinuous-file-ids.syms" \
Index: lit/SymbolFile/Breakpad/line-table-edgecases.test
===================================================================
--- lit/SymbolFile/Breakpad/line-table-edgecases.test
+++ lit/SymbolFile/Breakpad/line-table-edgecases.test
@@ -2,8 +2,6 @@
 # input contains a LINE record which does not belong to any function as well as
 # a FUNC record without any LINE records.
 
-# XFAIL: system-windows
-
 # RUN: yaml2obj %S/Inputs/basic-elf.yaml > %T/line-table-edgecases.out
 # RUN: %lldb %T/line-table-edgecases.out \
 # RUN:   -o "target symbols add -s line-table-edgecases.out %S/Inputs/line-table-edgecases.syms" \
Index: lit/SymbolFile/Breakpad/line-table-missing-file.test
===================================================================
--- lit/SymbolFile/Breakpad/line-table-missing-file.test
+++ lit/SymbolFile/Breakpad/line-table-missing-file.test
@@ -3,8 +3,6 @@
 # Right now, "something reasonable" means creating a line entry with an empty
 # file.
 
-# XFAIL: system-windows
-
 # RUN: yaml2obj %S/Inputs/basic-elf.yaml > %T/line-table-missing-file.out
 # RUN: %lldb %T/line-table-missing-file.out \
 # RUN:   -o "target symbols add -s line-table-missing-file.out %S/Inputs/line-table-missing-file.syms" \
Index: lit/SymbolFile/Breakpad/line-table-mixed-path-styles.test
===================================================================
--- /dev/null
+++ lit/SymbolFile/Breakpad/line-table-mixed-path-styles.test
@@ -0,0 +1,11 @@
+# RUN: yaml2obj %S/Inputs/basic-elf.yaml > %T/line-table-mixed-path-styles.out
+# RUN: %lldb %T/line-table-mixed-path-styles.out \
+# RUN:   -o "target symbols add -s line-table-mixed-path-styles.out %S/Inputs/line-table-mixed-path-styles.syms" \
+# RUN:   -s %s -o exit | FileCheck %s
+
+image dump line-table a.c
+# CHECK-LABEL: Line table for /tmp/a.c
+# CHECK-NEXT: 0x00000000004000b0: /tmp/a.c:1
+# CHECK-NEXT: 0x00000000004000b1: c:\tmp\b.c:1
+# CHECK-NEXT: 0x00000000004000b2:
+# CHECK-EMPTY:
Index: lit/SymbolFile/Breakpad/line-table.test
===================================================================
--- lit/SymbolFile/Breakpad/line-table.test
+++ lit/SymbolFile/Breakpad/line-table.test
@@ -1,5 +1,3 @@
-# XFAIL: system-windows
-
 # RUN: yaml2obj %S/Inputs/basic-elf.yaml > %T/line-table.out
 # RUN: %lldb %T/line-table.out -o "target symbols add -s line-table.out %S/Inputs/line-table.syms" \
 # RUN:   -s %s -o exit | FileCheck %s
Index: source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.cpp
===================================================================
--- source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.cpp
+++ source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.cpp
@@ -398,7 +398,9 @@
 
     if (record->Number >= m_files->size())
       m_files->resize(record->Number + 1);
-    (*m_files)[record->Number] = FileSpec(record->Name);
+    FileSpec::Style style = FileSpec::GuessPathStyle(record->Name)
+                                .getValueOr(FileSpec::Style::native);
+    (*m_files)[record->Number] = FileSpec(record->Name, style);
   }
 }
 
Index: source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp
+++ source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp
@@ -820,22 +820,19 @@
   if (!die)
     return;
 
-  auto guess = [](llvm::StringRef str) {
-    if (str.startswith("/"))
-      return FileSpec::Style::posix;
-    if (str.size() > 3 && llvm::isAlpha(str[0]) && str.substr(1, 2) == ":\\")
-      return FileSpec::Style::windows;
-    return FileSpec::Style::native;
-  };
   llvm::StringRef comp_dir = removeHostnameFromPathname(
       die->GetAttributeValueAsString(m_dwarf, this, DW_AT_comp_dir, NULL));
   if (!comp_dir.empty()) {
-    m_comp_dir = resolveCompDir(FileSpec(comp_dir, guess(comp_dir)));
+    FileSpec::Style comp_dir_style =
+        FileSpec::GuessPathStyle(comp_dir).getValueOr(FileSpec::Style::native);
+    m_comp_dir = resolveCompDir(FileSpec(comp_dir, comp_dir_style));
   } else {
     // Try to detect the style based on the DW_AT_name attribute, but just store
     // the detected style in the m_comp_dir field.
-    m_comp_dir = FileSpec("", guess(die->GetAttributeValueAsString(
-                                  m_dwarf, this, DW_AT_name, NULL)));
+    const char *name =
+        die->GetAttributeValueAsString(m_dwarf, this, DW_AT_name, NULL);
+    m_comp_dir = FileSpec(
+        "", FileSpec::GuessPathStyle(name).getValueOr(FileSpec::Style::native));
   }
 }
 
Index: source/Utility/FileSpec.cpp
===================================================================
--- source/Utility/FileSpec.cpp
+++ source/Utility/FileSpec.cpp
@@ -365,6 +365,17 @@
   return a == b;
 }
 
+llvm::Optional<FileSpec::Style> FileSpec::GuessPathStyle(llvm::StringRef absolute_path) {
+  if (absolute_path.startswith("/"))
+    return Style::posix;
+  if (absolute_path.startswith(R"(\\)"))
+    return Style::windows;
+  if (absolute_path.size() > 3 && llvm::isAlpha(absolute_path[0]) &&
+      absolute_path.substr(1, 2) == R"(:\)")
+    return Style::windows;
+  return llvm::None;
+}
+
 //------------------------------------------------------------------
 // Dump the object to the supplied stream. If the object contains a valid
 // directory name, it will be displayed followed by a directory delimiter, and
Index: unittests/Utility/FileSpecTest.cpp
===================================================================
--- unittests/Utility/FileSpecTest.cpp
+++ unittests/Utility/FileSpecTest.cpp
@@ -189,6 +189,17 @@
   }
 }
 
+TEST(FileSpecTest, GuessPathStyle) {
+  EXPECT_EQ(FileSpec::Style::posix, FileSpec::GuessPathStyle("/foo/bar.txt"));
+  EXPECT_EQ(FileSpec::Style::posix, FileSpec::GuessPathStyle("//net/bar.txt"));
+  EXPECT_EQ(FileSpec::Style::windows,
+            FileSpec::GuessPathStyle(R"(C:\foo.txt)"));
+  EXPECT_EQ(FileSpec::Style::windows,
+            FileSpec::GuessPathStyle(R"(\\net\foo.txt)"));
+  EXPECT_EQ(llvm::None, FileSpec::GuessPathStyle("foo.txt"));
+  EXPECT_EQ(llvm::None, FileSpec::GuessPathStyle("foo/bar.txt"));
+}
+
 TEST(FileSpecTest, GetNormalizedPath) {
   std::pair<const char *, const char *> posix_tests[] = {
       {"/foo/.././bar", "/bar"},