[Support] remove_dots: Remove .. from absolute paths.

/../foo is still a proper path after removing the dotdot. This should
now finally match https://9p.io/sys/doc/lexnames.html [Cleaning names].

llvm-svn: 284384

2 files changed, 12 insertions, 5 deletions

diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index 4374cba4988..b2d645779b0 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -707,11 +707,14 @@ static SmallString<256> remove_dots(StringRef path, bool remove_dot_dot) {
   for (StringRef C : llvm::make_range(path::begin(rel), path::end(rel))) {
     if (C == ".")
       continue;
-    // Leading ".." will remain in the path.
-    if (remove_dot_dot && C == ".." && !components.empty() &&
-        components.back() != "..") {
-      components.pop_back();
-      continue;
+    // Leading ".." will remain in the path unless it's at the root.
+    if (remove_dot_dot && C == "..") {
+      if (!components.empty() && components.back() != "..") {
+        components.pop_back();
+        continue;
+      }
+      if (path::is_absolute(path))
+        continue;
     }
     components.push_back(C);
   }
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
index 65bd1de8b70..7ddc5dbb396 100644
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -969,6 +969,8 @@ TEST(Support, RemoveDots) {
   EXPECT_EQ("c", remove_dots(".\\.\\c", true));
   EXPECT_EQ("..\\a\\c", remove_dots("..\\a\\b\\..\\c", true));
   EXPECT_EQ("..\\..\\a\\c", remove_dots("..\\..\\a\\b\\..\\c", true));
+  EXPECT_EQ("\\a\\c", remove_dots("\\..\\..\\a\\c", true));
+  EXPECT_EQ("\\a\\c", remove_dots("\\..\\a\\b\\\\..\\.\\.\\\\c", true));
 
   SmallString<64> Path1(".\\.\\c");
   EXPECT_TRUE(path::remove_dots(Path1, true));
@@ -982,6 +984,8 @@ TEST(Support, RemoveDots) {
   EXPECT_EQ("c", remove_dots("././c", true));
   EXPECT_EQ("../a/c", remove_dots("../a/b/../c", true));
   EXPECT_EQ("../../a/c", remove_dots("../../a/b/../c", true));
+  EXPECT_EQ("/a/c", remove_dots("/../../a/c", true));
+  EXPECT_EQ("/a/c", remove_dots("/../a/b//../././/c", true));
 
   SmallString<64> Path1("././c");
   EXPECT_TRUE(path::remove_dots(Path1, true));