From cb6f2646fd44c5274312c8fa782c4f339dfadad7 Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas@devlieghere.com>
Date: Tue, 6 Aug 2019 15:46:45 +0000
Subject: [PATCH] [Path] Fix bug in make_absolute logic

This fixes a bug for making path with a //net style root absolute. I
discovered the bug while writing a test case for the VFS, which uses
these paths because they're both legal absolute paths on Windows and
Unix.

Differential revision: https://reviews.llvm.org/D65675

llvm-svn: 368053
---
 llvm/lib/Support/Path.cpp       |  6 +++---
 llvm/unittests/Support/Path.cpp | 17 +++++++++++++----
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index c49260125dba..14def83802da 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -855,11 +855,11 @@ void make_absolute(const Twine &current_directory,
   StringRef p(path.data(), path.size());
 
   bool rootDirectory = path::has_root_directory(p);
-  bool rootName =
-      (real_style(Style::native) != Style::windows) || path::has_root_name(p);
+  bool rootName = path::has_root_name(p);
 
   // Already absolute.
-  if (rootName && rootDirectory)
+  if ((rootName || real_style(Style::native) != Style::windows) &&
+      rootDirectory)
     return;
 
   // All of the following conditions will need the current directory.
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
index 5e0581c945b0..1802b0031ad7 100644
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -185,10 +185,19 @@ TEST(Support, Path) {
     path::native(*i, temp_store);
   }
 
-  SmallString<32> Relative("foo.cpp");
-  sys::fs::make_absolute("/root", Relative);
-  Relative[5] = '/'; // Fix up windows paths.
-  ASSERT_EQ("/root/foo.cpp", Relative);
+  {
+    SmallString<32> Relative("foo.cpp");
+    sys::fs::make_absolute("/root", Relative);
+    Relative[5] = '/'; // Fix up windows paths.
+    ASSERT_EQ("/root/foo.cpp", Relative);
+  }
+
+  {
+    SmallString<32> Relative("foo.cpp");
+    sys::fs::make_absolute("//root", Relative);
+    Relative[6] = '/'; // Fix up windows paths.
+    ASSERT_EQ("//root/foo.cpp", Relative);
+  }
 }
 
 TEST(Support, FilenameParent) {