1 files changed, 137 insertions, 0 deletions
diff --git a/clang-tools-extra/clang-tidy/misc/MisleadingBidirectionalCheck.cpp b/clang-tools-extra/clang-tidy/misc/MisleadingBidirectionalCheck.cpp
new file mode 100644
index 0000000..4807567
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/misc/MisleadingBidirectionalCheck.cpp
@@ -0,0 +1,137 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "MisleadingBidirectionalCheck.h"
+
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Lex/Preprocessor.h"
+#include "llvm/Support/ConvertUTF.h"
+
+using namespace clang;
+using namespace clang::tidy::misc;
+
+static bool containsMisleadingBidi(StringRef Buffer,
+                                   bool HonorLineBreaks = true) {
+  const char *CurPtr = Buffer.begin();
+
+  enum BidiChar {
+    PS = 0x2029,
+    RLO = 0x202E,
+    RLE = 0x202B,
+    LRO = 0x202D,
+    LRE = 0x202A,
+    PDF = 0x202C,
+    RLI = 0x2067,
+    LRI = 0x2066,
+    FSI = 0x2068,
+    PDI = 0x2069
+  };
+
+  SmallVector<BidiChar> BidiContexts;
+
+  // Scan each character while maintaining a stack of opened bidi context.
+  // RLO/RLE/LRO/LRE all are closed by PDF while RLI LRI and FSI are closed by
+  // PDI. New lines reset the context count. Extra PDF / PDI are ignored.
+  //
+  // Warn if we end up with an unclosed context.
+  while (CurPtr < Buffer.end()) {
+    const unsigned char C = *CurPtr;
+    if (isASCII(C)) {
+      ++CurPtr;
+      const bool IsParagrapSep =
+          (C == 0xA || C == 0xD || (0x1C <= C && C <= 0x1E) || C == 0x85);
+      const bool IsSegmentSep = (C == 0x9 || C == 0xB || C == 0x1F);
+      if (IsParagrapSep || IsSegmentSep)
+        BidiContexts.clear();
+      continue;
+    }
+    llvm::UTF32 CodePoint = 0;
+    const llvm::ConversionResult Result = llvm::convertUTF8Sequence(
+        (const llvm::UTF8 **)&CurPtr, (const llvm::UTF8 *)Buffer.end(),
+        &CodePoint, llvm::strictConversion);
+
+    // If conversion fails, utf-8 is designed so that we can just try next char.
+    if (Result != llvm::conversionOK) {
+      ++CurPtr;
+      continue;
+    }
+
+    // Open a PDF context.
+    if (CodePoint == RLO || CodePoint == RLE || CodePoint == LRO ||
+        CodePoint == LRE)
+      BidiContexts.push_back(PDF);
+    // Close PDF Context.
+    else if (CodePoint == PDF) {
+      if (!BidiContexts.empty() && BidiContexts.back() == PDF)
+        BidiContexts.pop_back();
+    }
+    // Open a PDI Context.
+    else if (CodePoint == RLI || CodePoint == LRI || CodePoint == FSI)
+      BidiContexts.push_back(PDI);
+    // Close a PDI Context.
+    else if (CodePoint == PDI) {
+      auto R = llvm::find(llvm::reverse(BidiContexts), PDI);
+      if (R != BidiContexts.rend())
+        BidiContexts.resize(BidiContexts.rend() - R - 1);
+    }
+    // Line break or equivalent
+    else if (CodePoint == PS)
+      BidiContexts.clear();
+  }
+  return !BidiContexts.empty();
+}
+
+class MisleadingBidirectionalCheck::MisleadingBidirectionalHandler
+    : public CommentHandler {
+public:
+  MisleadingBidirectionalHandler(MisleadingBidirectionalCheck &Check)
+      : Check(Check) {}
+
+  bool HandleComment(Preprocessor &PP, SourceRange Range) override {
+    // FIXME: check that we are in a /* */ comment
+    const StringRef Text =
+        Lexer::getSourceText(CharSourceRange::getCharRange(Range),
+                             PP.getSourceManager(), PP.getLangOpts());
+
+    if (containsMisleadingBidi(Text, true))
+      Check.diag(
+          Range.getBegin(),
+          "comment contains misleading bidirectional Unicode characters");
+    return false;
+  }
+
+private:
+  MisleadingBidirectionalCheck &Check;
+};
+
+MisleadingBidirectionalCheck::MisleadingBidirectionalCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      Handler(std::make_unique<MisleadingBidirectionalHandler>(*this)) {}
+
+MisleadingBidirectionalCheck::~MisleadingBidirectionalCheck() = default;
+
+void MisleadingBidirectionalCheck::registerPPCallbacks(
+    const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
+  PP->addCommentHandler(Handler.get());
+}
+
+void MisleadingBidirectionalCheck::check(
+    const ast_matchers::MatchFinder::MatchResult &Result) {
+  if (const auto *SL = Result.Nodes.getNodeAs<StringLiteral>("strlit")) {
+    const StringRef Literal = SL->getBytes();
+    if (containsMisleadingBidi(Literal, false))
+      diag(SL->getBeginLoc(), "string literal contains misleading "
+                              "bidirectional Unicode characters");
+  }
+}
+
+void MisleadingBidirectionalCheck::registerMatchers(
+    ast_matchers::MatchFinder *Finder) {
+  Finder->addMatcher(ast_matchers::stringLiteral().bind("strlit"), this);
+}