[llvm-cov] Prevent llvm-cov from hanging when a symblink doesn't exist.

Summary:
Previous code hangs indefinitely when trying to iterate through a
symbol link file that points to an non-exist directory. This change
fixes the bug to make the addCollectedPath function exit ealier and
print out correct warning messages.

Patch by Yuke Liao (@liaoyuke).

Reviewers: Dor1s, vsk

Reviewed By: vsk

Subscribers: bruno, mgrang, llvm-commits

Differential Revision: https://reviews.llvm.org/D44960

llvm-svn: 329338

llvm/include/llvm/Support/FileSystem.h

@@ -956,14 +956,16 @@ class directory_iterator {
     SmallString<128> path_storage;
     ec = detail::directory_iterator_construct(
         *State, path.toStringRef(path_storage), FollowSymlinks);
+    update_error_code_for_current_entry(ec);
   }
 
   explicit directory_iterator(const directory_entry &de, std::error_code &ec,
                               bool follow_symlinks = true)
       : FollowSymlinks(follow_symlinks) {
     State = std::make_shared<detail::DirIterState>();
-    ec =
-        detail::directory_iterator_construct(*State, de.path(), FollowSymlinks);
+    ec = detail::directory_iterator_construct(
+        *State, de.path(), FollowSymlinks);
+    update_error_code_for_current_entry(ec);
   }
 
   /// Construct end iterator.
@@ -972,6 +974,7 @@ class directory_iterator {
   // No operator++ because we need error_code.
   directory_iterator &increment(std::error_code &ec) {
     ec = directory_iterator_increment(*State);
+    update_error_code_for_current_entry(ec);
     return *this;
   }
 
@@ -993,6 +996,24 @@ class directory_iterator {
   }
   // Other members as required by
   // C++ Std, 24.1.1 Input iterators [input.iterators]
+
+private:
+  // Checks if current entry is valid and populates error code. For example,
+  // current entry may not exist due to broken symbol links.
+  void update_error_code_for_current_entry(std::error_code &ec) {
+    // Bail out if error has already occured earlier to avoid overwriting it.
+    if (ec)
+      return;
+
+    // Empty directory entry is used to mark the end of an interation, it's not
+    // an error.
+    if (State->CurrentEntry == directory_entry())
+      return;
+
+    ErrorOr<basic_file_status> status = State->CurrentEntry.status();
+    if (!status)
+      ec = status.getError();
+  }
 };
 
 namespace detail {
@@ -1030,11 +1051,9 @@ class recursive_directory_iterator {
     if (State->HasNoPushRequest)
       State->HasNoPushRequest = false;
     else {
-      ErrorOr<basic_file_status> st = State->Stack.top()->status();
-      if (!st) return *this;
-      if (is_directory(*st)) {
+      ErrorOr<basic_file_status> status = State->Stack.top()->status();
+      if (status && is_directory(*status)) {
         State->Stack.push(directory_iterator(*State->Stack.top(), ec, Follow));
-        if (ec) return *this;
         if (State->Stack.top() != end_itr) {
           ++State->Level;
           return *this;

llvm/tools/llvm-cov/CodeCoverage.cpp

@@ -199,7 +199,7 @@ void CodeCoverageTool::collectPaths(const std::string &Path) {
     if (PathRemapping)
       addCollectedPath(Path);
     else
-      error("Missing source file", Path);
+      warning("Source file doesn't exist, proceeded by ignoring it.", Path);
     return;
   }
 
@@ -211,12 +211,16 @@ void CodeCoverageTool::collectPaths(const std::string &Path) {
   if (llvm::sys::fs::is_directory(Status)) {
     std::error_code EC;
     for (llvm::sys::fs::recursive_directory_iterator F(Path, EC), E;
-         F != E && !EC; F.increment(EC)) {
+         F != E; F.increment(EC)) {
+
+      if (EC) {
+        warning(EC.message(), F->path());
+        continue;
+      }
+
       if (llvm::sys::fs::is_regular_file(F->path()))
         addCollectedPath(F->path());
     }
-    if (EC)
-      warning(EC.message(), Path);
   }
 }
 

llvm/unittests/Support/Path.cpp

@@ -885,58 +885,91 @@ TEST_F(FileSystemTest, BrokenSymlinkDirectoryIteration) {
       fs::create_link("no_such_file", Twine(TestDirectory) + "/symlink/e"));
 
   typedef std::vector<std::string> v_t;
-  v_t visited;
-
-  // The directory iterator doesn't stat the file, so we should be able to
-  // iterate over the whole directory.
+  v_t VisitedNonBrokenSymlinks;
+  v_t VisitedBrokenSymlinks;
   std::error_code ec;
+
+  // Broken symbol links are expected to throw an error.
   for (fs::directory_iterator i(Twine(TestDirectory) + "/symlink", ec), e;
        i != e; i.increment(ec)) {
+    if (ec == std::make_error_code(std::errc::no_such_file_or_directory)) {
+      VisitedBrokenSymlinks.push_back(path::filename(i->path()));
+      continue;
+    }
+
     ASSERT_NO_ERROR(ec);
-    visited.push_back(path::filename(i->path()));
+    VisitedNonBrokenSymlinks.push_back(path::filename(i->path()));
   }
-  std::sort(visited.begin(), visited.end());
-  v_t expected = {"a", "b", "c", "d", "e"};
-  ASSERT_TRUE(visited.size() == expected.size());
-  ASSERT_TRUE(std::equal(visited.begin(), visited.end(), expected.begin()));
-  visited.clear();
-
-  // The recursive directory iterator has to stat the file, so we need to skip
-  // the broken symlinks.
-  for (fs::recursive_directory_iterator
-           i(Twine(TestDirectory) + "/symlink", ec),
-       e;
-       i != e; i.increment(ec)) {
-    ASSERT_NO_ERROR(ec);
-
-    ErrorOr<fs::basic_file_status> status = i->status();
-    if (status.getError() ==
-        std::make_error_code(std::errc::no_such_file_or_directory)) {
-      i.no_push();
+  std::sort(VisitedNonBrokenSymlinks.begin(), VisitedNonBrokenSymlinks.end());
+  std::sort(VisitedBrokenSymlinks.begin(), VisitedBrokenSymlinks.end());
+  v_t ExpectedNonBrokenSymlinks = {"b", "d"};
+  ASSERT_EQ(ExpectedNonBrokenSymlinks.size(), VisitedNonBrokenSymlinks.size());
+  ASSERT_TRUE(std::equal(VisitedNonBrokenSymlinks.begin(),
+                         VisitedNonBrokenSymlinks.end(),
+                         ExpectedNonBrokenSymlinks.begin()));
+  VisitedNonBrokenSymlinks.clear();
+
+  v_t ExpectedBrokenSymlinks = {"a", "c", "e"};
+  ASSERT_EQ(ExpectedBrokenSymlinks.size(), VisitedBrokenSymlinks.size());
+  ASSERT_TRUE(std::equal(VisitedBrokenSymlinks.begin(),
+                         VisitedBrokenSymlinks.end(),
+                         ExpectedBrokenSymlinks.begin()));
+  VisitedBrokenSymlinks.clear();
+
+  // Broken symbol links are expected to throw an error.
+  for (fs::recursive_directory_iterator i(
+      Twine(TestDirectory) + "/symlink", ec), e; i != e; i.increment(ec)) {
+    if (ec == std::make_error_code(std::errc::no_such_file_or_directory)) {
+      VisitedBrokenSymlinks.push_back(path::filename(i->path()));
       continue;
     }
 
-    visited.push_back(path::filename(i->path()));
+    ASSERT_NO_ERROR(ec);
+    VisitedNonBrokenSymlinks.push_back(path::filename(i->path()));
   }
-  std::sort(visited.begin(), visited.end());
-  expected = {"b", "bb", "d", "da", "dd", "ddd", "ddd"};
-  ASSERT_TRUE(visited.size() == expected.size());
-  ASSERT_TRUE(std::equal(visited.begin(), visited.end(), expected.begin()));
-  visited.clear();
-
-  // This recursive directory iterator doesn't follow symlinks, so we don't need
-  // to skip them.
-  for (fs::recursive_directory_iterator
-           i(Twine(TestDirectory) + "/symlink", ec, /*follow_symlinks=*/false),
-       e;
+  std::sort(VisitedNonBrokenSymlinks.begin(), VisitedNonBrokenSymlinks.end());
+  std::sort(VisitedBrokenSymlinks.begin(), VisitedBrokenSymlinks.end());
+  ExpectedNonBrokenSymlinks = {"b", "bb", "d", "da", "dd", "ddd", "ddd"};
+  ASSERT_EQ(ExpectedNonBrokenSymlinks.size(), VisitedNonBrokenSymlinks.size());
+  ASSERT_TRUE(std::equal(VisitedNonBrokenSymlinks.begin(),
+                         VisitedNonBrokenSymlinks.end(),
+                         ExpectedNonBrokenSymlinks.begin()));
+  VisitedNonBrokenSymlinks.clear();
+
+  ExpectedBrokenSymlinks = {"a", "ba", "bc", "c", "e"};
+  ASSERT_EQ(ExpectedBrokenSymlinks.size(), VisitedBrokenSymlinks.size());
+  ASSERT_TRUE(std::equal(VisitedBrokenSymlinks.begin(),
+                         VisitedBrokenSymlinks.end(),
+                         ExpectedBrokenSymlinks.begin()));
+  VisitedBrokenSymlinks.clear();
+
+  for (fs::recursive_directory_iterator i(
+      Twine(TestDirectory) + "/symlink", ec, /*follow_symlinks=*/false), e;
        i != e; i.increment(ec)) {
+    if (ec == std::make_error_code(std::errc::no_such_file_or_directory)) {
+      VisitedBrokenSymlinks.push_back(path::filename(i->path()));
+      continue;
+    }
+
     ASSERT_NO_ERROR(ec);
-    visited.push_back(path::filename(i->path()));
+    VisitedNonBrokenSymlinks.push_back(path::filename(i->path()));
   }
-  std::sort(visited.begin(), visited.end());
-  expected = {"a", "b", "ba", "bb", "bc", "c", "d", "da", "dd", "ddd", "e"};
-  ASSERT_TRUE(visited.size() == expected.size());
-  ASSERT_TRUE(std::equal(visited.begin(), visited.end(), expected.begin()));
+  std::sort(VisitedNonBrokenSymlinks.begin(), VisitedNonBrokenSymlinks.end());
+  std::sort(VisitedBrokenSymlinks.begin(), VisitedBrokenSymlinks.end());
+  ExpectedNonBrokenSymlinks = {"a", "b", "ba", "bb", "bc", "c", "d", "da", "dd",
+                               "ddd", "e"};
+  ASSERT_EQ(ExpectedNonBrokenSymlinks.size(), VisitedNonBrokenSymlinks.size());
+  ASSERT_TRUE(std::equal(VisitedNonBrokenSymlinks.begin(),
+                         VisitedNonBrokenSymlinks.end(),
+                         ExpectedNonBrokenSymlinks.begin()));
+  VisitedNonBrokenSymlinks.clear();
+
+  ExpectedBrokenSymlinks = {};
+  ASSERT_EQ(ExpectedBrokenSymlinks.size(), VisitedBrokenSymlinks.size());
+  ASSERT_TRUE(std::equal(VisitedBrokenSymlinks.begin(),
+                         VisitedBrokenSymlinks.end(),
+                         ExpectedBrokenSymlinks.begin()));
+  VisitedBrokenSymlinks.clear();
 
   ASSERT_NO_ERROR(fs::remove_directories(Twine(TestDirectory) + "/symlink"));
 }