Fix logic error when deserializing input file

* Also add a check for absolute paths in `isPathInStableDir`

Author: cyndyishida

clang/lib/Serialization/ASTReader.cpp

@@ -2616,6 +2616,18 @@ bool ASTReader::shouldDisableValidationForFile(
   return false;
 }
 
+namespace {
+
+std::pair<StringRef, StringRef>
+getUnresolvedInputFilenames(const ASTReader::RecordData &Record,
+                            const StringRef InputBlob) {
+  uint16_t AsRequestedLength = Record[7];
+  return {InputBlob.substr(0, AsRequestedLength),
+          InputBlob.substr(AsRequestedLength)};
+}
+
+} // namespace
+
 InputFileInfo ASTReader::getInputFileInfo(ModuleFile &F, unsigned ID) {
   // If this ID is bogus, just return an empty input file.
   if (ID == 0 || ID > F.InputFileInfosLoaded.size())
@@ -2659,11 +2671,12 @@ InputFileInfo ASTReader::getInputFileInfo(ModuleFile &F, unsigned ID) {
   R.Transient = static_cast<bool>(Record[4]);
   R.TopLevel = static_cast<bool>(Record[5]);
   R.ModuleMap = static_cast<bool>(Record[6]);
-  uint16_t AsRequestedLength = Record[7];
-  R.UnresolvedImportedFilenameAsRequested = Blob.substr(0, AsRequestedLength);
-  R.UnresolvedImportedFilename = Blob.substr(AsRequestedLength);
-  if (R.UnresolvedImportedFilename.empty())
-    R.UnresolvedImportedFilename = R.UnresolvedImportedFilenameAsRequested;
+  auto [UnresolvedFilenameAsRequested, UnresolvedFilename] =
+      getUnresolvedInputFilenames(Record, Blob);
+  R.UnresolvedImportedFilenameAsRequested = UnresolvedFilenameAsRequested;
+  R.UnresolvedImportedFilename = UnresolvedFilename.empty()
+                                     ? UnresolvedFilenameAsRequested
+                                     : UnresolvedFilename;
 
   Expected<llvm::BitstreamEntry> MaybeEntry = Cursor.advance();
   if (!MaybeEntry) // FIXME this drops errors on the floor.
@@ -5834,13 +5847,27 @@ bool ASTReader::readASTFileControlBlock(
           break;
         case INPUT_FILE:
           bool Overridden = static_cast<bool>(Record[3]);
-          const size_t FilenameAsRequestedLength = Record[7] + 1;
-          auto ResolvedFilenameAsRequested = ResolveImportedPath(
-              PathBuf, Blob.substr(0, FilenameAsRequestedLength), ModuleDir);
-          StringRef ExternalFilename = Blob.substr(FilenameAsRequestedLength);
+
+          auto [UnresolvedFilenameAsRequested, UnresolvedFilename] =
+              getUnresolvedInputFilenames(Record, Blob);
+          TemporarilyOwnedStringRef ResolvedFilenameAsRequested =
+              ResolveImportedPath(PathBuf, UnresolvedFilenameAsRequested,
+                                  ModuleDir);
+          const std::string ResolvedFilenameAsRequestedStr =
+              ResolvedFilenameAsRequested->str();
+
+          std::string ResolvedFilenameStr;
+          if (!UnresolvedFilename.empty()) {
+            SmallString<0> FilenameBuf;
+            FilenameBuf.reserve(256);
+            auto ResolvedFilename =
+                ResolveImportedPath(FilenameBuf, UnresolvedFilename, ModuleDir);
+            ResolvedFilenameStr = ResolvedFilename->str();
+          }
+
           shouldContinue = Listener.visitInputFile(
-              ResolvedFilenameAsRequested->str(), ExternalFilename,
-              isSystemFile, Overridden,
+              ResolvedFilenameAsRequestedStr, ResolvedFilenameStr, isSystemFile,
+              Overridden,
               /*IsExplicitModule=*/false);
           break;
         }

clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

@@ -226,11 +226,14 @@ void dependencies::resetBenignCodeGenOptions(frontend::ActionKind ProgramAction,
 
 bool dependencies::isPathInStableDir(const ArrayRef<StringRef> Directories,
                                      const StringRef Input) {
+  using namespace llvm::sys;
+
+  if (!path::is_absolute(Input))
+    return false;
+
   auto PathStartsWith = [](StringRef Prefix, StringRef Path) {
-    auto PrefixIt = llvm::sys::path::begin(Prefix),
-         PrefixEnd = llvm::sys::path::end(Prefix);
-    for (auto PathIt = llvm::sys::path::begin(Path),
-              PathEnd = llvm::sys::path::end(Path);
+    auto PrefixIt = path::begin(Prefix), PrefixEnd = path::end(Prefix);
+    for (auto PathIt = path::begin(Path), PathEnd = path::end(Path);
          PrefixIt != PrefixEnd && PathIt != PathEnd; ++PrefixIt, ++PathIt) {
       if (*PrefixIt != *PathIt)
         return false;