Misleading identifier detection

[serge-sans-paille]

Summary

Detect identifiers with right-to-left ordering through clang-tidy.
It detects a class of attack similar to the ones described in https://www.trojansource.codes/trojan-source.pdf

[rsmith]

Looks good as far as it goes (though I've not checked your classification functions are correct).

We should have some detection for RTL characters in string literals and comments too, at least when there is no subsequent character with strong LTR directionality. Neither " nor */ has strong directionality, so both א" and א*/ can potentially leave us in an RTL state. For example:

// This is "א" then + then "ג".
"א" + "ג"

// This is `a` then `/*א*/` then `*` then `-` then `/*ג*/` then `b`, aka "a * - b" not "a - * b".
a /*א*/ * - /*ג*/ b

clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.cpp

3

Please fix

20

(throughout).

135–136

As in the other patch, we could recover here by skipping until we find a valid UTF-8 lead byte. It's not important here since invalid UTF-8 won't be accepted in an identifier anyway, but might be important if we start checking strings and comments for RTL characters too.

[serge-sans-paille]

• fix formatting
• added documentation
• *not* doing the extra work wrt. unicode error recovery

[carlosgalvezp]

• Add check to list of checks: https://github.com/llvm/llvm-project/blob/main/clang-tools-extra/docs/clang-tidy/checks/list.rst
• Mention check in the Release Notes: https://github.com/llvm/llvm-project/blob/main/clang-tools-extra/docs/ReleaseNotes.rst

[serge-sans-paille]

Also update clang-tidy doc index

[serge-sans-paille]

Update release note too.

[carlosgalvezp]

Looks good, I guess the license issue still needs to be sorted out?

clang-tools-extra/docs/clang-tidy/checks/misc-misleading-identifier.rst

7

characters

11

example

[serge-sans-paille]

AKAIU, the licensing issue doesn't impact that particular review, only the one on confusable identifiers.

[carlosgalvezp]

Ok! I don't really know what applies when you take part of a file, so I'll leave that up to people who know. I don't know how to remove the "Requested changes" from here so I'll just remove myself from reviewer.

PS: I don't know what AKAIU means, nor can I find the answer in Google :)

[serge-sans-paille]

In D112914#3102728, @carlosgalvezp wrote:

Ok! I don't really know what applies when you take part of a file, so I'll leave that up to people who know. I don't know how to remove the "Requested changes" from here so I'll just remove myself from reviewer.

That's a valid question, but I guess that using spec content is ok... not 100% sure though.

PS: I don't know what AKAIU means, nor can I find the answer in Google :)

I meant AFAIU, I'm so skilled I can make typo in acronyms :-)

[serge-sans-paille]

Minor typos

[rsmith]

clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.h

3

This needs fixing too.

[serge-sans-paille]

Fix comments

[rsmith]

In D112914#3102728, @carlosgalvezp wrote:

I don't know how to remove the "Requested changes" from here so I'll just remove myself from reviewer.

Marking the change as accepted should overwrite the "requested changes" state.

[RKSimon]

@serge-sans-paille Any luck with a fix for all the buildbot failures or should we revert ? https://lab.llvm.org/buildbot/#/builders/109/builds/25932

[aaronpuchert]

clang-tools-extra/docs/clang-tidy/checks/misc-misleading-identifier.rst

12

Sphinx can't parse that (perhaps unsurprisingly), could you declare that as having no language?

Warning, treated as error:
/home/buildbot/llvm-build-dir/clang-tools-sphinx-docs/llvm/src/clang-tools-extra/docs/clang-tidy/checks/misc-misleading-identifier.rst:12:Could not lex literal_block as "c". Highlighting skipped.

Should be reproducible by building docs-clang-tools-html (might need -j1).

[serge-sans-paille]

Yep, I'm currently validating locally, I somehow messed up a rebase :-/

[RKSimon]

In D112914#3119103, @serge-sans-paille wrote:

Yep, I'm currently validating locally, I somehow messed up a rebase :-/

I'm sorry @serge-sans-paille I missed this reply before pushing the revert :(

[thakis]

The test seems to trigger an assert: http://45.33.8.238/linux/60293/step_9.txt

Please take a look!

[serge-sans-paille]

In D112914#3119704, @thakis wrote:

The test seems to trigger an assert: http://45.33.8.238/linux/60293/step_9.txt

Please take a look!

It's getting late here: Reverted, I'll have a look tomorrow.

[RKSimon]

@serge-sans-paille Still failing on https://lab.llvm.org/buildbot/#/builders/139/builds/12974

[RKSimon]

clang-tools-extra/test/clang-tidy/checkers/misc-misleading-identifier.cpp

3

@serge-sans-paille Any chance you can remove the include and just forward declare printf()?

[serge-sans-paille]

clang-tools-extra/test/clang-tidy/checkers/misc-misleading-identifier.cpp

3

Sure, I'll prepare a patch.

[aaron.ballman]

clang-tools-extra/docs/clang-tidy/checks/misc-misleading-identifier.rst

12

I fixed this in ac8c813b89f62efcaff4d0c92fdf1a5dd29d795d as the bot was red.

clang-tools-extra/clang-tidy/misc/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   FrontendOpenMP
   Support
   )
 
 add_clang_library(clangTidyMiscModule
   DefinitionsInHeadersCheck.cpp
   MiscTidyModule.cpp
+  MisleadingIdentifier.cpp
   MisplacedConstCheck.cpp
   NewDeleteOverloadsCheck.cpp
   NoRecursionCheck.cpp
   NonCopyableObjects.cpp
   NonPrivateMemberVariablesInClassesCheck.cpp
   RedundantExpressionCheck.cpp
   StaticAssertCheck.cpp
   ThrowByValueCatchByReferenceCheck.cpp

clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.h

+//===--- MisleadingIdentifierCheck.h - clang-tidy ---------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_MISLEADINGIDENTIFIERCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_MISLEADINGIDENTIFIERCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+class MisleadingIdentifierCheck : public ClangTidyCheck {
+public:
+  MisleadingIdentifierCheck(StringRef Name, ClangTidyContext *Context);
+  ~MisleadingIdentifierCheck();
+
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_MISLEADINGIDENTIFIERCHECK_H

clang-tools-extra/clang-tidy/misc/MisleadingIdentifier.cpp

+//===--- MisleadingIdentifier.cpp - clang-tidy-----------------------------===//
+//
+// 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 "MisleadingIdentifier.h"
+
+#include "clang/Frontend/CompilerInstance.h"
+#include "llvm/Support/ConvertUTF.h"
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+// See https://www.unicode.org/Public/14.0.0/ucd/extracted/DerivedBidiClass.txt
+static bool isUnassignedAL(llvm::UTF32 CP) {
+  return (0x0600 <= CP && CP <= 0x07BF) || (0x0860 <= CP && CP <= 0x08FF) ||
+         (0xFB50 <= CP && CP <= 0xFDCF) || (0xFDF0 <= CP && CP <= 0xFDFF) ||
+         (0xFE70 <= CP && CP <= 0xFEFF) ||
+         (0x00010D00 <= CP && CP <= 0x00010D3F) ||
+         (0x00010F30 <= CP && CP <= 0x00010F6F) ||
+         (0x0001EC70 <= CP && CP <= 0x0001ECBF) ||
+         (0x0001ED00 <= CP && CP <= 0x0001ED4F) ||
+         (0x0001EE00 <= CP && CP <= 0x0001EEFF);
+}
+
+// See https://www.unicode.org/Public/14.0.0/ucd/extracted/DerivedBidiClass.txt
+static bool isUnassignedR(llvm::UTF32 CP) {
+  return (0x0590 <= CP && CP <= 0x05FF) || (0x07C0 <= CP && CP <= 0x085F) ||
+         (0xFB1D <= CP && CP <= 0xFB4F) ||
+         (0x00010800 <= CP && CP <= 0x00010CFF) ||
+         (0x00010D40 <= CP && CP <= 0x00010F2F) ||
+         (0x00010F70 <= CP && CP <= 0x00010FFF) ||
+         (0x0001E800 <= CP && CP <= 0x0001EC6F) ||
+         (0x0001ECC0 <= CP && CP <= 0x0001ECFF) ||
+         (0x0001ED50 <= CP && CP <= 0x0001EDFF) ||
+         (0x0001EF00 <= CP && CP <= 0x0001EFFF);
+}
+
+// See https://www.unicode.org/Public/14.0.0/ucd/extracted/DerivedBidiClass.txt
+static bool isR(llvm::UTF32 CP) {
+  return (CP == 0x0590) || (CP == 0x05BE) || (CP == 0x05C0) || (CP == 0x05C3) ||
+         (CP == 0x05C6) || (0x05C8 <= CP && CP <= 0x05CF) ||
+         (0x05D0 <= CP && CP <= 0x05EA) || (0x05EB <= CP && CP <= 0x05EE) ||
+         (0x05EF <= CP && CP <= 0x05F2) || (0x05F3 <= CP && CP <= 0x05F4) ||
+         (0x05F5 <= CP && CP <= 0x05FF) || (0x07C0 <= CP && CP <= 0x07C9) ||
+         (0x07CA <= CP && CP <= 0x07EA) || (0x07F4 <= CP && CP <= 0x07F5) ||
+         (CP == 0x07FA) || (0x07FB <= CP && CP <= 0x07FC) ||
+         (0x07FE <= CP && CP <= 0x07FF) || (0x0800 <= CP && CP <= 0x0815) ||
+         (CP == 0x081A) || (CP == 0x0824) || (CP == 0x0828) ||
+         (0x082E <= CP && CP <= 0x082F) || (0x0830 <= CP && CP <= 0x083E) ||
+         (CP == 0x083F) || (0x0840 <= CP && CP <= 0x0858) ||
+         (0x085C <= CP && CP <= 0x085D) || (CP == 0x085E) || (CP == 0x085F) ||
+         (CP == 0x200F) || (CP == 0xFB1D) || (0xFB1F <= CP && CP <= 0xFB28) ||
+         (0xFB2A <= CP && CP <= 0xFB36) || (CP == 0xFB37) ||
+         (0xFB38 <= CP && CP <= 0xFB3C) || (CP == 0xFB3D) || (CP == 0xFB3E) ||
+         (CP == 0xFB3F) || (0xFB40 <= CP && CP <= 0xFB41) || (CP == 0xFB42) ||
+         (0xFB43 <= CP && CP <= 0xFB44) || (CP == 0xFB45) ||
+         (0xFB46 <= CP && CP <= 0xFB4F) || (0x10800 <= CP && CP <= 0x10805) ||
+         (0x10806 <= CP && CP <= 0x10807) || (CP == 0x10808) ||
+         (CP == 0x10809) || (0x1080A <= CP && CP <= 0x10835) ||
+         (CP == 0x10836) || (0x10837 <= CP && CP <= 0x10838) ||
+         (0x10839 <= CP && CP <= 0x1083B) || (CP == 0x1083C) ||
+         (0x1083D <= CP && CP <= 0x1083E) || (0x1083F <= CP && CP <= 0x10855) ||
+         (CP == 0x10856) || (CP == 0x10857) ||
+         (0x10858 <= CP && CP <= 0x1085F) || (0x10860 <= CP && CP <= 0x10876) ||
+         (0x10877 <= CP && CP <= 0x10878) || (0x10879 <= CP && CP <= 0x1087F) ||
+         (0x10880 <= CP && CP <= 0x1089E) || (0x1089F <= CP && CP <= 0x108A6) ||
+         (0x108A7 <= CP && CP <= 0x108AF) || (0x108B0 <= CP && CP <= 0x108DF) ||
+         (0x108E0 <= CP && CP <= 0x108F2) || (CP == 0x108F3) ||
+         (0x108F4 <= CP && CP <= 0x108F5) || (0x108F6 <= CP && CP <= 0x108FA) ||
+         (0x108FB <= CP && CP <= 0x108FF) || (0x10900 <= CP && CP <= 0x10915) ||
+         (0x10916 <= CP && CP <= 0x1091B) || (0x1091C <= CP && CP <= 0x1091E) ||
+         (0x10920 <= CP && CP <= 0x10939) || (0x1093A <= CP && CP <= 0x1093E) ||
+         (CP == 0x1093F) || (0x10940 <= CP && CP <= 0x1097F) ||
+         (0x10980 <= CP && CP <= 0x109B7) || (0x109B8 <= CP && CP <= 0x109BB) ||
+         (0x109BC <= CP && CP <= 0x109BD) || (0x109BE <= CP && CP <= 0x109BF) ||
+         (0x109C0 <= CP && CP <= 0x109CF) || (0x109D0 <= CP && CP <= 0x109D1) ||
+         (0x109D2 <= CP && CP <= 0x109FF) || (CP == 0x10A00) ||
+         (CP == 0x10A04) || (0x10A07 <= CP && CP <= 0x10A0B) ||
+         (0x10A10 <= CP && CP <= 0x10A13) || (CP == 0x10A14) ||
+         (0x10A15 <= CP && CP <= 0x10A17) || (CP == 0x10A18) ||
+         (0x10A19 <= CP && CP <= 0x10A35) || (0x10A36 <= CP && CP <= 0x10A37) ||
+         (0x10A3B <= CP && CP <= 0x10A3E) || (0x10A40 <= CP && CP <= 0x10A48) ||
+         (0x10A49 <= CP && CP <= 0x10A4F) || (0x10A50 <= CP && CP <= 0x10A58) ||
+         (0x10A59 <= CP && CP <= 0x10A5F) || (0x10A60 <= CP && CP <= 0x10A7C) ||
+         (0x10A7D <= CP && CP <= 0x10A7E) || (CP == 0x10A7F) ||
+         (0x10A80 <= CP && CP <= 0x10A9C) || (0x10A9D <= CP && CP <= 0x10A9F) ||
+         (0x10AA0 <= CP && CP <= 0x10ABF) || (0x10AC0 <= CP && CP <= 0x10AC7) ||
+         (CP == 0x10AC8) || (0x10AC9 <= CP && CP <= 0x10AE4) ||
+         (0x10AE7 <= CP && CP <= 0x10AEA) || (0x10AEB <= CP && CP <= 0x10AEF) ||
+         (0x10AF0 <= CP && CP <= 0x10AF6) || (0x10AF7 <= CP && CP <= 0x10AFF) ||
+         (0x10B00 <= CP && CP <= 0x10B35) || (0x10B36 <= CP && CP <= 0x10B38) ||
+         (0x10B40 <= CP && CP <= 0x10B55) || (0x10B56 <= CP && CP <= 0x10B57) ||
+         (0x10B58 <= CP && CP <= 0x10B5F) || (0x10B60 <= CP && CP <= 0x10B72) ||
+         (0x10B73 <= CP && CP <= 0x10B77) || (0x10B78 <= CP && CP <= 0x10B7F) ||
+         (0x10B80 <= CP && CP <= 0x10B91) || (0x10B92 <= CP && CP <= 0x10B98) ||
+         (0x10B99 <= CP && CP <= 0x10B9C) || (0x10B9D <= CP && CP <= 0x10BA8) ||
+         (0x10BA9 <= CP && CP <= 0x10BAF) || (0x10BB0 <= CP && CP <= 0x10BFF) ||
+         (0x10C00 <= CP && CP <= 0x10C48) || (0x10C49 <= CP && CP <= 0x10C7F) ||
+         (0x10C80 <= CP && CP <= 0x10CB2) || (0x10CB3 <= CP && CP <= 0x10CBF) ||
+         (0x10CC0 <= CP && CP <= 0x10CF2) || (0x10CF3 <= CP && CP <= 0x10CF9) ||
+         (0x10CFA <= CP && CP <= 0x10CFF) || (0x10D40 <= CP && CP <= 0x10E5F) ||
+         (CP == 0x10E7F) || (0x10E80 <= CP && CP <= 0x10EA9) ||
+         (CP == 0x10EAA) || (CP == 0x10EAD) ||
+         (0x10EAE <= CP && CP <= 0x10EAF) || (0x10EB0 <= CP && CP <= 0x10EB1) ||
+         (0x10EB2 <= CP && CP <= 0x10EFF) || (0x10F00 <= CP && CP <= 0x10F1C) ||
+         (0x10F1D <= CP && CP <= 0x10F26) || (CP == 0x10F27) ||
+         (0x10F28 <= CP && CP <= 0x10F2F) || (0x10F70 <= CP && CP <= 0x10F81) ||
+         (0x10F86 <= CP && CP <= 0x10F89) || (0x10F8A <= CP && CP <= 0x10FAF) ||
+         (0x10FB0 <= CP && CP <= 0x10FC4) || (0x10FC5 <= CP && CP <= 0x10FCB) ||
+         (0x10FCC <= CP && CP <= 0x10FDF) || (0x10FE0 <= CP && CP <= 0x10FF6) ||
+         (0x10FF7 <= CP && CP <= 0x10FFF) || (0x1E800 <= CP && CP <= 0x1E8C4) ||
+         (0x1E8C5 <= CP && CP <= 0x1E8C6) || (0x1E8C7 <= CP && CP <= 0x1E8CF) ||
+         (0x1E8D7 <= CP && CP <= 0x1E8FF) || (0x1E900 <= CP && CP <= 0x1E943) ||
+         (CP == 0x1E94B) || (0x1E94C <= CP && CP <= 0x1E94F) ||
+         (0x1E950 <= CP && CP <= 0x1E959) || (0x1E95A <= CP && CP <= 0x1E95D) ||
+         (0x1E95E <= CP && CP <= 0x1E95F) || (0x1E960 <= CP && CP <= 0x1EC6F) ||
+         (0x1ECC0 <= CP && CP <= 0x1ECFF) || (0x1ED50 <= CP && CP <= 0x1EDFF);
+}
+
+static bool hasRTLCharacters(StringRef Buffer) {
+  const char *CurPtr = Buffer.begin();
+  const char *EndPtr = Buffer.end();
+  while (CurPtr < EndPtr) {
+    llvm::UTF32 CodePoint;
+    llvm::ConversionResult Result = llvm::convertUTF8Sequence(
+        (const llvm::UTF8 **)&CurPtr, (const llvm::UTF8 *)EndPtr, &CodePoint,
+        llvm::strictConversion);
+    if (Result != llvm::conversionOK)
+      break;
+    if (isUnassignedAL(CodePoint) || isUnassignedR(CodePoint) || isR(CodePoint))
+      return true;
+  }
+  return false;
+}
+
+MisleadingIdentifierCheck::MisleadingIdentifierCheck(StringRef Name,
+                                                     ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context) {}
+
+MisleadingIdentifierCheck::~MisleadingIdentifierCheck() = default;
+
+void MisleadingIdentifierCheck::check(
+    const ast_matchers::MatchFinder::MatchResult &Result) {
+  if (const auto *ND = Result.Nodes.getNodeAs<NamedDecl>("nameddecl")) {
+    StringRef NDName = ND->getName();
+    if (hasRTLCharacters(NDName))
+      diag(ND->getBeginLoc(), "identifier has right-to-left codepoints");
+  }
+}
+
+void MisleadingIdentifierCheck::registerMatchers(
+    ast_matchers::MatchFinder *Finder) {
+  Finder->addMatcher(ast_matchers::namedDecl().bind("nameddecl"), this);
+}
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang

clang-tools-extra/docs/ReleaseNotes.rst

- New :doc:`cppcoreguidelines-virtual-class-destructor
   protected and non-virtual.
 
 - New :doc:`readability-identifier-length
   <clang-tidy/checks/readability-identifier-length>` check.
 
   Reports identifiers whose names are too short. Currently checks local
   variables and function parameters only.
 
-
 - New :doc:`readability-data-pointer <clang-tidy/checks/readability-data-pointer>` check.
 
   Finds cases where code could use ``data()`` rather than the address of the
   element at index 0 in a container.
 
+- New :doc:`misc-misleading-identifier <clang-tidy/checks/misc-misleading-identifier>` check.
+
+  Reports identifier with unicode right-to-left characters.
+
 New check aliases
 ^^^^^^^^^^^^^^^^^
 
 - New alias :doc:`cert-err33-c
   <clang-tidy/checks/cert-err33-c>` to
   :doc:`bugprone-unused-return-value
   <clang-tidy/checks/bugprone-unused-return-value>` was added.
 

clang-tools-extra/docs/clang-tidy/checks/list.rst

.. csv-table::
    `llvm-namespace-comment <llvm-namespace-comment.html>`_,
    `llvm-prefer-isa-or-dyn-cast-in-conditionals <llvm-prefer-isa-or-dyn-cast-in-conditionals.html>`_, "Yes"
    `llvm-prefer-register-over-unsigned <llvm-prefer-register-over-unsigned.html>`_, "Yes"
    `llvm-twine-local <llvm-twine-local.html>`_, "Yes"
    `llvmlibc-callee-namespace <llvmlibc-callee-namespace.html>`_,
    `llvmlibc-implementation-in-namespace <llvmlibc-implementation-in-namespace.html>`_,
    `llvmlibc-restrict-system-libc-headers <llvmlibc-restrict-system-libc-headers.html>`_, "Yes"
    `misc-definitions-in-headers <misc-definitions-in-headers.html>`_, "Yes"
+   `misc-misleading-identifier <misc-mileading-identifier.html>`_,
    `misc-misplaced-const <misc-misplaced-const.html>`_,
    `misc-new-delete-overloads <misc-new-delete-overloads.html>`_,
    `misc-no-recursion <misc-no-recursion.html>`_,
    `misc-non-copyable-objects <misc-non-copyable-objects.html>`_,
    `misc-non-private-member-variables-in-classes <misc-non-private-member-variables-in-classes.html>`_,
    `misc-redundant-expression <misc-redundant-expression.html>`_, "Yes"
    `misc-static-assert <misc-static-assert.html>`_, "Yes"
    `misc-throw-by-value-catch-by-reference <misc-throw-by-value-catch-by-reference.html>`_,
.. csv-table:: Aliases..
    `hicpp-use-equals-default <hicpp-use-equals-default.html>`_, `modernize-use-equals-default <modernize-use-equals-default.html>`_, "Yes"
    `hicpp-use-equals-delete <hicpp-use-equals-delete.html>`_, `modernize-use-equals-delete <modernize-use-equals-delete.html>`_, "Yes"
    `hicpp-use-noexcept <hicpp-use-noexcept.html>`_, `modernize-use-noexcept <modernize-use-noexcept.html>`_, "Yes"
    `hicpp-use-nullptr <hicpp-use-nullptr.html>`_, `modernize-use-nullptr <modernize-use-nullptr.html>`_, "Yes"
    `hicpp-use-override <hicpp-use-override.html>`_, `modernize-use-override <modernize-use-override.html>`_, "Yes"
    `hicpp-vararg <hicpp-vararg.html>`_, `cppcoreguidelines-pro-type-vararg <cppcoreguidelines-pro-type-vararg.html>`_,
    `llvm-else-after-return <llvm-else-after-return.html>`_, `readability-else-after-return <readability-else-after-return.html>`_, "Yes"
    `llvm-qualified-auto <llvm-qualified-auto.html>`_, `readability-qualified-auto <readability-qualified-auto.html>`_, "Yes"
+   
 
 

clang-tools-extra/docs/clang-tidy/checks/misc-misleading-identifier.rst

+.. title:: clang-tidy - misc-misleading-identifier
+
+misc-misleading-identifier
+==========================
+
+Finds identifiers that contain Unicode characters with right-to-left direction,
+which can be confusing as they may change the understanding of a whole statement
+line, as described in `Trojan Source <https://trojansource.codes>`_.
+
+An example of such misleading code follows:
+
+.. code-block:: c
+
+    #include <stdio.h>
+
+    short int א = (short int)0;
+    short int ג = (short int)12345;
+
+    int main() {
+      int א = ג; // a local variable, set to zero?
+      printf("ג is %d\n", ג);
+      printf("א is %d\n", א);
+    }

clang-tools-extra/test/clang-tidy/checkers/misc-misleading-identifier.cpp

+// RUN: %check_clang_tidy %s misc-misleading-identifier %t
+
+#include <stdio.h>
+
+// CHECK-MESSAGES: :[[@LINE+1]]:1: warning: identifier has right-to-left codepoints
+short int א = (short int)0;
+// CHECK-MESSAGES: :[[@LINE+1]]:1: warning: identifier has right-to-left codepoints
+short int ג = (short int)12345;
+
+int main() {
+  // CHECK-MESSAGES: :[[@LINE+1]]:5: warning: identifier has right-to-left codepoints
+  int א = ג; // a local variable, set to zero?
+  printf("ג is %d\n", ג);
+  printf("א is %d\n", א);
+}