[clang] Extension: allow recursive macros (PR #65851)

via cfe-commits cfe-commits at lists.llvm.org
Sun Sep 24 04:17:10 PDT 2023


https://github.com/kelbon updated https://github.com/llvm/llvm-project/pull/65851

>From d10ce5dd9e49fe85eac2e1f93a65cb27b511a71f Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Sat, 9 Sep 2023 17:51:15 +0400
Subject: [PATCH 01/13] add define2 pp directive

---
 clang/include/clang/Basic/TokenKinds.def |  1 +
 clang/include/clang/Lex/MacroInfo.h      | 19 +++++++++----------
 clang/include/clang/Lex/Preprocessor.h   |  2 +-
 clang/lib/Basic/IdentifierTable.cpp      |  2 ++
 clang/lib/Format/WhitespaceManager.cpp   |  2 +-
 clang/lib/Lex/MacroInfo.cpp              |  3 ++-
 clang/lib/Lex/PPDirectives.cpp           | 16 +++++++++++-----
 7 files changed, 27 insertions(+), 18 deletions(-)

diff --git a/clang/include/clang/Basic/TokenKinds.def b/clang/include/clang/Basic/TokenKinds.def
index 72e8df8c793a7b6..b227a6a5632f496 100644
--- a/clang/include/clang/Basic/TokenKinds.def
+++ b/clang/include/clang/Basic/TokenKinds.def
@@ -115,6 +115,7 @@ PPKEYWORD(__include_macros)
 
 // C99 6.10.3 - Macro Replacement.
 PPKEYWORD(define)
+PPKEYWORD(define2)
 PPKEYWORD(undef)
 
 // C99 6.10.4 - Line Control.
diff --git a/clang/include/clang/Lex/MacroInfo.h b/clang/include/clang/Lex/MacroInfo.h
index 00c1c3866bbd9ca..4f0c8e987610e50 100644
--- a/clang/include/clang/Lex/MacroInfo.h
+++ b/clang/include/clang/Lex/MacroInfo.h
@@ -102,6 +102,10 @@ class MacroInfo {
   /// like \#define A A.
   bool IsDisabled : 1;
 
+  // True if 'define2' used,
+  // ignores 'IsDisabled' and enables expansion anyway
+  bool AllowRecurse : 1;
+
   /// True if this macro is either defined in the main file and has
   /// been used, or if it is not defined in the main file.
   ///
@@ -278,18 +282,13 @@ class MacroInfo {
   /// Return true if this macro is enabled.
   ///
   /// In other words, that we are not currently in an expansion of this macro.
-  bool isEnabled() const { return !IsDisabled; }
-
-  void EnableMacro() {
-    assert(IsDisabled && "Cannot enable an already-enabled macro!");
-    IsDisabled = false;
-  }
+  bool isEnabled() const { return AllowRecurse || !IsDisabled; }
+  void setAllowRecursive(bool Allow) { AllowRecurse = Allow; }
+  bool isAllowRecurse() const { return AllowRecurse; }
 
-  void DisableMacro() {
-    assert(!IsDisabled && "Cannot disable an already-disabled macro!");
-    IsDisabled = true;
-  }
+  void EnableMacro() { IsDisabled = false; }
 
+  void DisableMacro() { IsDisabled = true; }
   /// Determine whether this macro was used for a header guard.
   bool isUsedForHeaderGuard() const { return UsedForHeaderGuard; }
 
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index 575d08b83fd3a02..01eac0939fe9e21 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -2754,7 +2754,7 @@ class Preprocessor {
   void replayPreambleConditionalStack();
 
   // Macro handling.
-  void HandleDefineDirective(Token &Tok, bool ImmediatelyAfterHeaderGuard);
+  void HandleDefineDirective(Token &Tok, bool ImmediatelyAfterHeaderGuard, bool AllowRecurse);
   void HandleUndefDirective();
 
   // Conditional Inclusion.
diff --git a/clang/lib/Basic/IdentifierTable.cpp b/clang/lib/Basic/IdentifierTable.cpp
index e5599d545541085..7300825ff6b826a 100644
--- a/clang/lib/Basic/IdentifierTable.cpp
+++ b/clang/lib/Basic/IdentifierTable.cpp
@@ -431,6 +431,8 @@ tok::PPKeywordKind IdentifierInfo::getPPKeywordID() const {
   unsigned Len = getLength();
   if (Len < 2) return tok::pp_not_keyword;
   const char *Name = getNameStart();
+  if (std::string_view(Name, Len) == "define2")
+    return tok::pp_define2;
   switch (HASH(Len, Name[0], Name[2])) {
   default: return tok::pp_not_keyword;
   CASE( 2, 'i', '\0', if);
diff --git a/clang/lib/Format/WhitespaceManager.cpp b/clang/lib/Format/WhitespaceManager.cpp
index b7bd8d27dc976b1..d8ab76d6761553e 100644
--- a/clang/lib/Format/WhitespaceManager.cpp
+++ b/clang/lib/Format/WhitespaceManager.cpp
@@ -743,7 +743,7 @@ void WhitespaceManager::alignConsecutiveMacros() {
     if (!Current || Current->isNot(tok::identifier))
       return false;
 
-    if (!Current->Previous || Current->Previous->isNot(tok::pp_define))
+    if (!Current->Previous || !Current->Previous->isOneOf(tok::pp_define, tok::pp_define2))
       return false;
 
     // For a macro function, 0 spaces are required between the
diff --git a/clang/lib/Lex/MacroInfo.cpp b/clang/lib/Lex/MacroInfo.cpp
index 39bb0f44eff25ba..9c3619c7c909304 100644
--- a/clang/lib/Lex/MacroInfo.cpp
+++ b/clang/lib/Lex/MacroInfo.cpp
@@ -50,7 +50,7 @@ static_assert(MacroInfoSizeChecker<sizeof(void *)>::AsExpected,
 MacroInfo::MacroInfo(SourceLocation DefLoc)
     : Location(DefLoc), IsDefinitionLengthCached(false), IsFunctionLike(false),
       IsC99Varargs(false), IsGNUVarargs(false), IsBuiltinMacro(false),
-      HasCommaPasting(false), IsDisabled(false), IsUsed(false),
+      HasCommaPasting(false), IsDisabled(false), AllowRecurse(false), IsUsed(false),
       IsAllowRedefinitionsWithoutWarning(false), IsWarnIfUnused(false),
       UsedForHeaderGuard(false) {}
 
@@ -157,6 +157,7 @@ LLVM_DUMP_METHOD void MacroInfo::dump() const {
   if (IsBuiltinMacro) Out << " builtin";
   if (IsDisabled) Out << " disabled";
   if (IsUsed) Out << " used";
+  if (AllowRecurse) Out << " allow_recurse";
   if (IsAllowRedefinitionsWithoutWarning)
     Out << " allow_redefinitions_without_warning";
   if (IsWarnIfUnused) Out << " warn_if_unused";
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 7edcb0577c2b25a..01b77a39437a30d 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -1111,7 +1111,11 @@ void Preprocessor::HandleSkippedDirectiveWhileUsingPCH(Token &Result,
   if (const IdentifierInfo *II = Result.getIdentifierInfo()) {
     if (II->getPPKeywordID() == tok::pp_define) {
       return HandleDefineDirective(Result,
-                                   /*ImmediatelyAfterHeaderGuard=*/false);
+                                   /*ImmediatelyAfterHeaderGuard=*/false, /*AllowRecurse=*/false);
+    }
+    if (II->getPPKeywordID() == tok::pp_define2) {
+      return HandleDefineDirective(Result,
+                                   /*ImmediatelyAfterHeaderGuard=*/false, /*AllowRecurse=*/true);
     }
     if (SkippingUntilPCHThroughHeader &&
         II->getPPKeywordID() == tok::pp_include) {
@@ -1250,7 +1254,9 @@ void Preprocessor::HandleDirective(Token &Result) {
 
     // C99 6.10.3 - Macro Replacement.
     case tok::pp_define:
-      return HandleDefineDirective(Result, ImmediatelyAfterTopLevelIfndef);
+      return HandleDefineDirective(Result, ImmediatelyAfterTopLevelIfndef, false);
+    case tok::pp_define2:
+      return HandleDefineDirective(Result, ImmediatelyAfterTopLevelIfndef, true);
     case tok::pp_undef:
       return HandleUndefDirective();
 
@@ -3036,10 +3042,10 @@ static bool isObjCProtectedMacro(const IdentifierInfo *II) {
          II->isStr("__unsafe_unretained") || II->isStr("__autoreleasing");
 }
 
-/// HandleDefineDirective - Implements \#define.  This consumes the entire macro
+/// HandleDefineDirective - Implements \#define and define2. This consumes the entire macro
 /// line then lets the caller lex the next real token.
 void Preprocessor::HandleDefineDirective(
-    Token &DefineTok, const bool ImmediatelyAfterHeaderGuard) {
+    Token &DefineTok, const bool ImmediatelyAfterHeaderGuard, bool AllowRecurse) {
   ++NumDefined;
 
   Token MacroNameTok;
@@ -3064,7 +3070,7 @@ void Preprocessor::HandleDefineDirective(
       MacroNameTok, ImmediatelyAfterHeaderGuard);
 
   if (!MI) return;
-
+  MI->setAllowRecursive(AllowRecurse);
   if (MacroShadowsKeyword &&
       !isConfigurationPattern(MacroNameTok, MI, getLangOpts())) {
     Diag(MacroNameTok, diag::warn_pp_macro_hides_keyword);

>From 4e175402aa82403ee5281c5cd60250cb3c1536fc Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Sun, 10 Sep 2023 16:00:45 +0400
Subject: [PATCH 02/13] add recursion depth limit and tests

---
 .../include/clang/Basic/DiagnosticLexKinds.td |  2 ++
 clang/include/clang/Lex/MacroInfo.h           | 33 ++++++++++++-------
 clang/lib/Lex/MacroInfo.cpp                   |  4 +--
 clang/lib/Lex/TokenLexer.cpp                  |  3 +-
 .../test/Preprocessor/macro_vaopt_expand.cpp  | 20 +++++++++++
 clang/test/Preprocessor/recursive_macro.cpp   | 13 ++++++++
 6 files changed, 60 insertions(+), 15 deletions(-)
 create mode 100644 clang/test/Preprocessor/recursive_macro.cpp

diff --git a/clang/include/clang/Basic/DiagnosticLexKinds.td b/clang/include/clang/Basic/DiagnosticLexKinds.td
index 940cca67368492f..f940fa01a3d2f38 100644
--- a/clang/include/clang/Basic/DiagnosticLexKinds.td
+++ b/clang/include/clang/Basic/DiagnosticLexKinds.td
@@ -440,6 +440,8 @@ def err_pp_missing_lparen_in_vaopt_use : Error<
 def err_pp_vaopt_nested_use : Error<
   "__VA_OPT__ cannot be nested within its own replacement tokens">;
 
+def err_pp_macro_recursion_depth_limit_exceeded : Error<
+  "macro recursion depth limit exceeded">;
 def err_vaopt_paste_at_start : Error<
   "'##' cannot appear at start of __VA_OPT__ argument">;
 
diff --git a/clang/include/clang/Lex/MacroInfo.h b/clang/include/clang/Lex/MacroInfo.h
index 4f0c8e987610e50..267292083058645 100644
--- a/clang/include/clang/Lex/MacroInfo.h
+++ b/clang/include/clang/Lex/MacroInfo.h
@@ -65,6 +65,12 @@ class MacroInfo {
 
   /// Length in characters of the macro definition.
   mutable unsigned DefinitionLength;
+
+  enum : uint16_t { recursion_depth_limit = 16'000 };
+  /// recursion depth,
+  /// > 0 if we have started an expansion of this macro already.
+  /// for 'define' max is 1, for 'define2' max is depth limit
+  uint16_t Depth = 0;
   mutable bool IsDefinitionLengthCached : 1;
 
   /// True if this macro is function-like, false if it is object-like.
@@ -96,14 +102,7 @@ class MacroInfo {
   //===--------------------------------------------------------------------===//
   // State that changes as the macro is used.
 
-  /// True if we have started an expansion of this macro already.
-  ///
-  /// This disables recursive expansion, which would be quite bad for things
-  /// like \#define A A.
-  bool IsDisabled : 1;
-
-  // True if 'define2' used,
-  // ignores 'IsDisabled' and enables expansion anyway
+  // True if 'define2' used, enables expansion anyway
   bool AllowRecurse : 1;
 
   /// True if this macro is either defined in the main file and has
@@ -282,13 +281,23 @@ class MacroInfo {
   /// Return true if this macro is enabled.
   ///
   /// In other words, that we are not currently in an expansion of this macro.
-  bool isEnabled() const { return AllowRecurse || !IsDisabled; }
+  bool isEnabled() const {
+    // macro disabled if depth exceeds and stops infinite recursion
+    if (AllowRecurse)
+      return Depth < recursion_depth_limit;
+    return Depth == 0;
+  }
   void setAllowRecursive(bool Allow) { AllowRecurse = Allow; }
   bool isAllowRecurse() const { return AllowRecurse; }
 
-  void EnableMacro() { IsDisabled = false; }
-
-  void DisableMacro() { IsDisabled = true; }
+  void EnableMacro() {
+    assert(Depth != 0 && "Cannot enable not disabled macro");
+    --Depth;
+  }
+  // returns false if max recursion depth exceeded
+  [[nodiscard]] bool TryDisableMacro() {
+    return ++Depth < recursion_depth_limit;
+  }
   /// Determine whether this macro was used for a header guard.
   bool isUsedForHeaderGuard() const { return UsedForHeaderGuard; }
 
diff --git a/clang/lib/Lex/MacroInfo.cpp b/clang/lib/Lex/MacroInfo.cpp
index 9c3619c7c909304..110e3232b66dc14 100644
--- a/clang/lib/Lex/MacroInfo.cpp
+++ b/clang/lib/Lex/MacroInfo.cpp
@@ -50,7 +50,7 @@ static_assert(MacroInfoSizeChecker<sizeof(void *)>::AsExpected,
 MacroInfo::MacroInfo(SourceLocation DefLoc)
     : Location(DefLoc), IsDefinitionLengthCached(false), IsFunctionLike(false),
       IsC99Varargs(false), IsGNUVarargs(false), IsBuiltinMacro(false),
-      HasCommaPasting(false), IsDisabled(false), AllowRecurse(false), IsUsed(false),
+      HasCommaPasting(false), AllowRecurse(false), IsUsed(false),
       IsAllowRedefinitionsWithoutWarning(false), IsWarnIfUnused(false),
       UsedForHeaderGuard(false) {}
 
@@ -155,7 +155,7 @@ LLVM_DUMP_METHOD void MacroInfo::dump() const {
   // FIXME: Dump locations.
   Out << "MacroInfo " << this;
   if (IsBuiltinMacro) Out << " builtin";
-  if (IsDisabled) Out << " disabled";
+  if (!isEnabled()) Out << " disabled";
   if (IsUsed) Out << " used";
   if (AllowRecurse) Out << " allow_recurse";
   if (IsAllowRedefinitionsWithoutWarning)
diff --git a/clang/lib/Lex/TokenLexer.cpp b/clang/lib/Lex/TokenLexer.cpp
index 856d5682727fe3d..c51aec4fc17110d 100644
--- a/clang/lib/Lex/TokenLexer.cpp
+++ b/clang/lib/Lex/TokenLexer.cpp
@@ -88,7 +88,8 @@ void TokenLexer::Init(Token &Tok, SourceLocation ELEnd, MacroInfo *MI,
   // Mark the macro as currently disabled, so that it is not recursively
   // expanded.  The macro must be disabled only after argument pre-expansion of
   // function-like macro arguments occurs.
-  Macro->DisableMacro();
+  if (!Macro->TryDisableMacro())
+    PP.Diag(Tok, diag::err_pp_macro_recursion_depth_limit_exceeded);
 }
 
 /// Create a TokenLexer for the specified token stream.  This does not
diff --git a/clang/test/Preprocessor/macro_vaopt_expand.cpp b/clang/test/Preprocessor/macro_vaopt_expand.cpp
index 5eb0facb83f7364..9766b081516fd09 100644
--- a/clang/test/Preprocessor/macro_vaopt_expand.cpp
+++ b/clang/test/Preprocessor/macro_vaopt_expand.cpp
@@ -148,3 +148,23 @@
 
 #undef F
 #undef G
+
+#define merge_all_expand2(a, b) a ## b
+#define merge_all_expand(a, b) merge_all_expand2(a, b)
+#define2 concat_all(head, ...) merge_all_expand(head, __VA_OPT__(concat_all(__VA_ARGS__)))
+29: concat_all(aa, bb, cc)
+30: [concat_all()]
+// CHECK: 29: aabbcc
+// CHECK: 30: []
+
+#undef merge_all_expand
+#undef merge_all_expand2
+#undef concat_all
+
+#define2 reverse(head, ...) __VA_OPT__(reverse(__VA_ARGS__) , ) head
+
+31: reverse(1, 2, 3)
+
+// CHECK: 31: 3, 2, 1
+
+#undef reverse
diff --git a/clang/test/Preprocessor/recursive_macro.cpp b/clang/test/Preprocessor/recursive_macro.cpp
new file mode 100644
index 000000000000000..0fee436bf4d9ce0
--- /dev/null
+++ b/clang/test/Preprocessor/recursive_macro.cpp
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 %s -Eonly -std=c++11 -pedantic -verify
+
+#define2 A A
+
+A //expected-error {{macro recursion depth limit exceeded}}
+
+#undef A
+
+#define2 boom(x) boom(x)
+
+boom(5)  //expected-error {{macro recursion depth limit exceeded}}
+
+#undef boom

>From 6ab7f4eba17c8174e09a50fedfcd3e1a22d44d80 Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Mon, 11 Sep 2023 12:03:36 +0400
Subject: [PATCH 03/13] rewrite Lexer recursion to loop

---
 clang/lib/Lex/Lexer.cpp                       | 32 +++++++++----------
 clang/lib/Lex/PPMacroExpansion.cpp            |  2 ++
 .../test/Preprocessor/macro_vaopt_expand.cpp  |  4 +--
 3 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 37c3e4175d4736e..178bcc08a72e208 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -847,26 +847,26 @@ bool Lexer::isAtEndOfMacroExpansion(SourceLocation loc,
                                     const SourceManager &SM,
                                     const LangOptions &LangOpts,
                                     SourceLocation *MacroEnd) {
-  assert(loc.isValid() && loc.isMacroID() && "Expected a valid macro loc");
+  for(SourceLocation expansionLoc; true;loc = expansionLoc) {
+    assert(loc.isValid() && loc.isMacroID() && "Expected a valid macro loc");
 
-  SourceLocation spellLoc = SM.getSpellingLoc(loc);
-  unsigned tokLen = MeasureTokenLength(spellLoc, SM, LangOpts);
-  if (tokLen == 0)
-    return false;
+    SourceLocation spellLoc = SM.getSpellingLoc(loc);
+    unsigned tokLen = MeasureTokenLength(spellLoc, SM, LangOpts);
+    if (tokLen == 0)
+      return false;
 
-  SourceLocation afterLoc = loc.getLocWithOffset(tokLen);
-  SourceLocation expansionLoc;
-  if (!SM.isAtEndOfImmediateMacroExpansion(afterLoc, &expansionLoc))
-    return false;
+    SourceLocation afterLoc = loc.getLocWithOffset(tokLen);
+    if (!SM.isAtEndOfImmediateMacroExpansion(afterLoc, &expansionLoc))
+      return false;
 
-  if (expansionLoc.isFileID()) {
-    // No other macro expansions.
-    if (MacroEnd)
-      *MacroEnd = expansionLoc;
-    return true;
+    if (expansionLoc.isFileID()) {
+      // No other macro expansions.
+      if (MacroEnd)
+        *MacroEnd = expansionLoc;
+      return true;
+    }
   }
-
-  return isAtEndOfMacroExpansion(expansionLoc, SM, LangOpts, MacroEnd);
+  llvm_unreachable("");
 }
 
 static CharSourceRange makeRangeFromFileLocs(CharSourceRange Range,
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index ec6a084f228f32d..313475cfd0e113c 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -614,6 +614,8 @@ bool Preprocessor::HandleMacroExpandedIdentifier(Token &Identifier,
     if (IdentifierInfo *NewII = Identifier.getIdentifierInfo()) {
       if (MacroInfo *NewMI = getMacroInfo(NewII))
         if (!NewMI->isEnabled() || NewMI == MI) {
+          if (NewMI->isAllowRecurse() && NewMI == MI)
+            Diag(Identifier, diag::err_pp_macro_recursion_depth_limit_exceeded);
           Identifier.setFlag(Token::DisableExpand);
           // Don't warn for "#define X X" like "#define bool bool" from
           // stdbool.h.
diff --git a/clang/test/Preprocessor/macro_vaopt_expand.cpp b/clang/test/Preprocessor/macro_vaopt_expand.cpp
index 9766b081516fd09..17be324fdd71392 100644
--- a/clang/test/Preprocessor/macro_vaopt_expand.cpp
+++ b/clang/test/Preprocessor/macro_vaopt_expand.cpp
@@ -163,8 +163,8 @@
 
 #define2 reverse(head, ...) __VA_OPT__(reverse(__VA_ARGS__) , ) head
 
-31: reverse(1, 2, 3)
+31: reverse(1,2,3)
 
-// CHECK: 31: 3, 2, 1
+// CHECK: 31: 3,2,1
 
 #undef reverse

>From 6c126e8d6cb1fc97059d57b86e908465a2128873 Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Mon, 11 Sep 2023 13:54:55 +0400
Subject: [PATCH 04/13] more tests

---
 .../test/Preprocessor/macro_vaopt_expand.cpp  | 20 -------------------
 clang/test/Preprocessor/recursive_macro.cpp   | 13 ------------
 2 files changed, 33 deletions(-)
 delete mode 100644 clang/test/Preprocessor/recursive_macro.cpp

diff --git a/clang/test/Preprocessor/macro_vaopt_expand.cpp b/clang/test/Preprocessor/macro_vaopt_expand.cpp
index 17be324fdd71392..5eb0facb83f7364 100644
--- a/clang/test/Preprocessor/macro_vaopt_expand.cpp
+++ b/clang/test/Preprocessor/macro_vaopt_expand.cpp
@@ -148,23 +148,3 @@
 
 #undef F
 #undef G
-
-#define merge_all_expand2(a, b) a ## b
-#define merge_all_expand(a, b) merge_all_expand2(a, b)
-#define2 concat_all(head, ...) merge_all_expand(head, __VA_OPT__(concat_all(__VA_ARGS__)))
-29: concat_all(aa, bb, cc)
-30: [concat_all()]
-// CHECK: 29: aabbcc
-// CHECK: 30: []
-
-#undef merge_all_expand
-#undef merge_all_expand2
-#undef concat_all
-
-#define2 reverse(head, ...) __VA_OPT__(reverse(__VA_ARGS__) , ) head
-
-31: reverse(1,2,3)
-
-// CHECK: 31: 3,2,1
-
-#undef reverse
diff --git a/clang/test/Preprocessor/recursive_macro.cpp b/clang/test/Preprocessor/recursive_macro.cpp
deleted file mode 100644
index 0fee436bf4d9ce0..000000000000000
--- a/clang/test/Preprocessor/recursive_macro.cpp
+++ /dev/null
@@ -1,13 +0,0 @@
-// RUN: %clang_cc1 %s -Eonly -std=c++11 -pedantic -verify
-
-#define2 A A
-
-A //expected-error {{macro recursion depth limit exceeded}}
-
-#undef A
-
-#define2 boom(x) boom(x)
-
-boom(5)  //expected-error {{macro recursion depth limit exceeded}}
-
-#undef boom

>From fe01de795a9db1ff3c6bfde827b893e4059e24d5 Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Mon, 11 Sep 2023 13:55:51 +0400
Subject: [PATCH 05/13] test files

---
 .../Preprocessor/macro_infinite_recursion.cpp | 13 +++++++++
 clang/test/Preprocessor/macro_recursion.cpp   | 28 +++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 clang/test/Preprocessor/macro_infinite_recursion.cpp
 create mode 100644 clang/test/Preprocessor/macro_recursion.cpp

diff --git a/clang/test/Preprocessor/macro_infinite_recursion.cpp b/clang/test/Preprocessor/macro_infinite_recursion.cpp
new file mode 100644
index 000000000000000..cac8e7abbec5af3
--- /dev/null
+++ b/clang/test/Preprocessor/macro_infinite_recursion.cpp
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 %s -Eonly -std=c++11 -pedantic -verify
+
+#define2 A A
+
+A //expected-error {{macro recursion depth limit exceeded}}
+
+#undef A
+
+#define2 A(x) A(x)
+
+A(5)  //expected-error {{macro recursion depth limit exceeded}}
+
+#undef A
diff --git a/clang/test/Preprocessor/macro_recursion.cpp b/clang/test/Preprocessor/macro_recursion.cpp
new file mode 100644
index 000000000000000..da3e6157efc0f60
--- /dev/null
+++ b/clang/test/Preprocessor/macro_recursion.cpp
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -E %s -std=c++20 | FileCheck %s
+
+#define merge_all_expand2(a, b) a ## b
+#define merge_all_expand(a, b) merge_all_expand2(a, b)
+#define2 concat_all(head, ...) merge_all_expand(head, __VA_OPT__(concat_all(__VA_ARGS__)))
+0: concat_all(aa, bb, cc)
+1: [concat_all()]
+// CHECK: 0: aabbcc
+// CHECK: 1: []
+
+#undef merge_all_expand
+#undef merge_all_expand2
+#undef concat_all
+
+#define2 reverse(head, ...) __VA_OPT__(reverse(__VA_ARGS__) , ) head
+
+2: reverse(1,2,3)
+
+// CHECK: 2: 3,2,1
+
+#undef reverse
+
+#define2 fold_left(op, head, ...) ( __VA_OPT__(fold_left(op, __VA_ARGS__) op) head )
+
+3: fold_left(+, 1, 2, 3, 4)
+// CHECK: 3: ((((4) + 3) + 2) + 1)
+
+#undef fold_left

>From abe0bd0489f6dce25431dccdeafac8063a239f8f Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Mon, 11 Sep 2023 14:23:17 +0400
Subject: [PATCH 06/13] whitespaces

---
 clang/test/Preprocessor/macro_recursion.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/Preprocessor/macro_recursion.cpp b/clang/test/Preprocessor/macro_recursion.cpp
index da3e6157efc0f60..a7a69e4ba08b146 100644
--- a/clang/test/Preprocessor/macro_recursion.cpp
+++ b/clang/test/Preprocessor/macro_recursion.cpp
@@ -16,7 +16,7 @@
 
 2: reverse(1,2,3)
 
-// CHECK: 2: 3,2,1
+// CHECK: 2: 3 , 2 , 1
 
 #undef reverse
 

>From a28be970bf5c440bbecf7146d27e51dca42ba4cd Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Mon, 11 Sep 2023 16:10:20 +0400
Subject: [PATCH 07/13] whitespaces in tests

---
 clang/test/Preprocessor/macro_recursion.cpp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/clang/test/Preprocessor/macro_recursion.cpp b/clang/test/Preprocessor/macro_recursion.cpp
index a7a69e4ba08b146..cd415ce1a95e463 100644
--- a/clang/test/Preprocessor/macro_recursion.cpp
+++ b/clang/test/Preprocessor/macro_recursion.cpp
@@ -2,7 +2,7 @@
 
 #define merge_all_expand2(a, b) a ## b
 #define merge_all_expand(a, b) merge_all_expand2(a, b)
-#define2 concat_all(head, ...) merge_all_expand(head, __VA_OPT__(concat_all(__VA_ARGS__)))
+#define2 concat_all(head, ...)merge_all_expand(head,__VA_OPT__(concat_all(__VA_ARGS__)))
 0: concat_all(aa, bb, cc)
 1: [concat_all()]
 // CHECK: 0: aabbcc
@@ -12,17 +12,17 @@
 #undef merge_all_expand2
 #undef concat_all
 
-#define2 reverse(head, ...) __VA_OPT__(reverse(__VA_ARGS__) , ) head
+#define2 reverse(head, ...)__VA_OPT__(reverse(__VA_ARGS__),)head
 
 2: reverse(1,2,3)
 
-// CHECK: 2: 3 , 2 , 1
+// CHECK: 2: 3,2,1
 
 #undef reverse
 
-#define2 fold_left(op, head, ...) ( __VA_OPT__(fold_left(op, __VA_ARGS__) op) head )
+#define2 fold_left(op, head, ...)(__VA_OPT__(fold_left(op,__VA_ARGS__)op)head)
 
 3: fold_left(+, 1, 2, 3, 4)
-// CHECK: 3: ((((4) + 3) + 2) + 1)
+// CHECK: 3: ((((4)+3)+2)+1)
 
 #undef fold_left

>From 8555660c576eac3f34537bf0233aefbfcb6828a2 Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Tue, 12 Sep 2023 01:53:45 +0400
Subject: [PATCH 08/13] remove redundant HandleDefineDirective argument

---
 clang/include/clang/Lex/MacroInfo.h    | 23 ++++++++++++-----------
 clang/include/clang/Lex/Preprocessor.h |  2 +-
 clang/lib/Lex/PPDirectives.cpp         | 15 +++++----------
 3 files changed, 18 insertions(+), 22 deletions(-)

diff --git a/clang/include/clang/Lex/MacroInfo.h b/clang/include/clang/Lex/MacroInfo.h
index 267292083058645..54b1d7193dbe613 100644
--- a/clang/include/clang/Lex/MacroInfo.h
+++ b/clang/include/clang/Lex/MacroInfo.h
@@ -66,11 +66,9 @@ class MacroInfo {
   /// Length in characters of the macro definition.
   mutable unsigned DefinitionLength;
 
-  enum : uint16_t { recursion_depth_limit = 16'000 };
-  /// recursion depth,
-  /// > 0 if we have started an expansion of this macro already.
-  /// for 'define' max is 1, for 'define2' max is depth limit
-  uint16_t Depth = 0;
+  /// True if 'define2' used, enables expansion anyway
+  bool AllowRecurse : 1;
+
   mutable bool IsDefinitionLengthCached : 1;
 
   /// True if this macro is function-like, false if it is object-like.
@@ -102,9 +100,6 @@ class MacroInfo {
   //===--------------------------------------------------------------------===//
   // State that changes as the macro is used.
 
-  // True if 'define2' used, enables expansion anyway
-  bool AllowRecurse : 1;
-
   /// True if this macro is either defined in the main file and has
   /// been used, or if it is not defined in the main file.
   ///
@@ -120,6 +115,12 @@ class MacroInfo {
   /// Whether this macro was used as header guard.
   bool UsedForHeaderGuard : 1;
 
+  enum : uint16_t { recursion_depth_limit = 16'000 };
+  /// recursion depth,
+  /// > 0 if we have started an expansion of this macro already.
+  /// for 'define' max is 1, for 'define2' max is depth limit
+  uint16_t Depth = 0;
+
   // Only the Preprocessor gets to create these.
   MacroInfo(SourceLocation DefLoc);
 
@@ -283,9 +284,7 @@ class MacroInfo {
   /// In other words, that we are not currently in an expansion of this macro.
   bool isEnabled() const {
     // macro disabled if depth exceeds and stops infinite recursion
-    if (AllowRecurse)
-      return Depth < recursion_depth_limit;
-    return Depth == 0;
+    return AllowRecurse ? Depth < recursion_depth_limit : Depth == 0;
   }
   void setAllowRecursive(bool Allow) { AllowRecurse = Allow; }
   bool isAllowRecurse() const { return AllowRecurse; }
@@ -296,8 +295,10 @@ class MacroInfo {
   }
   // returns false if max recursion depth exceeded
   [[nodiscard]] bool TryDisableMacro() {
+    assert((AllowRecurse || Depth == 0) && "Cannot disable an already-disabled macro!");
     return ++Depth < recursion_depth_limit;
   }
+
   /// Determine whether this macro was used for a header guard.
   bool isUsedForHeaderGuard() const { return UsedForHeaderGuard; }
 
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index 01eac0939fe9e21..575d08b83fd3a02 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -2754,7 +2754,7 @@ class Preprocessor {
   void replayPreambleConditionalStack();
 
   // Macro handling.
-  void HandleDefineDirective(Token &Tok, bool ImmediatelyAfterHeaderGuard, bool AllowRecurse);
+  void HandleDefineDirective(Token &Tok, bool ImmediatelyAfterHeaderGuard);
   void HandleUndefDirective();
 
   // Conditional Inclusion.
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 01b77a39437a30d..06b81985749aa25 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -1109,13 +1109,9 @@ class Preprocessor::ResetMacroExpansionHelper {
 void Preprocessor::HandleSkippedDirectiveWhileUsingPCH(Token &Result,
                                                        SourceLocation HashLoc) {
   if (const IdentifierInfo *II = Result.getIdentifierInfo()) {
-    if (II->getPPKeywordID() == tok::pp_define) {
+    if (II->getPPKeywordID() == tok::pp_define || II->getPPKeywordID() == tok::pp_define2) {
       return HandleDefineDirective(Result,
-                                   /*ImmediatelyAfterHeaderGuard=*/false, /*AllowRecurse=*/false);
-    }
-    if (II->getPPKeywordID() == tok::pp_define2) {
-      return HandleDefineDirective(Result,
-                                   /*ImmediatelyAfterHeaderGuard=*/false, /*AllowRecurse=*/true);
+                                   /*ImmediatelyAfterHeaderGuard=*/false);
     }
     if (SkippingUntilPCHThroughHeader &&
         II->getPPKeywordID() == tok::pp_include) {
@@ -1254,9 +1250,8 @@ void Preprocessor::HandleDirective(Token &Result) {
 
     // C99 6.10.3 - Macro Replacement.
     case tok::pp_define:
-      return HandleDefineDirective(Result, ImmediatelyAfterTopLevelIfndef, false);
     case tok::pp_define2:
-      return HandleDefineDirective(Result, ImmediatelyAfterTopLevelIfndef, true);
+      return HandleDefineDirective(Result, ImmediatelyAfterTopLevelIfndef);
     case tok::pp_undef:
       return HandleUndefDirective();
 
@@ -3045,7 +3040,7 @@ static bool isObjCProtectedMacro(const IdentifierInfo *II) {
 /// HandleDefineDirective - Implements \#define and define2. This consumes the entire macro
 /// line then lets the caller lex the next real token.
 void Preprocessor::HandleDefineDirective(
-    Token &DefineTok, const bool ImmediatelyAfterHeaderGuard, bool AllowRecurse) {
+    Token &DefineTok, const bool ImmediatelyAfterHeaderGuard) {
   ++NumDefined;
 
   Token MacroNameTok;
@@ -3070,7 +3065,7 @@ void Preprocessor::HandleDefineDirective(
       MacroNameTok, ImmediatelyAfterHeaderGuard);
 
   if (!MI) return;
-  MI->setAllowRecursive(AllowRecurse);
+  MI->setAllowRecursive(DefineTok.getIdentifierInfo()->getPPKeywordID() == tok::pp_define2);
   if (MacroShadowsKeyword &&
       !isConfigurationPattern(MacroNameTok, MI, getLangOpts())) {
     Diag(MacroNameTok, diag::warn_pp_macro_hides_keyword);

>From 49d7fa2e638f3903375f6f1de8443c63ff909a5d Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Sun, 24 Sep 2023 13:42:56 +0400
Subject: [PATCH 09/13] __THIS_MACRO__

---
 clang/include/clang/Lex/MacroInfo.h           | 18 ++++++++----
 clang/include/clang/Lex/Preprocessor.h        |  6 ++++
 clang/lib/Lex/PPMacroExpansion.cpp            | 29 +++++++++++++++++++
 clang/lib/Lex/Preprocessor.cpp                |  1 +
 .../Preprocessor/macro_infinite_recursion.cpp |  6 ++--
 clang/test/Preprocessor/macro_recursion.cpp   |  6 ++--
 6 files changed, 55 insertions(+), 11 deletions(-)

diff --git a/clang/include/clang/Lex/MacroInfo.h b/clang/include/clang/Lex/MacroInfo.h
index 54b1d7193dbe613..8b91d33e971b752 100644
--- a/clang/include/clang/Lex/MacroInfo.h
+++ b/clang/include/clang/Lex/MacroInfo.h
@@ -55,7 +55,7 @@ class MacroInfo {
   IdentifierInfo **ParameterList = nullptr;
 
   /// This is the list of tokens that the macro is defined to.
-  const Token *ReplacementTokens = nullptr;
+  Token *ReplacementTokens = nullptr;
 
   /// \see ParameterList
   unsigned NumParameters = 0;
@@ -186,8 +186,11 @@ class MacroInfo {
   param_iterator param_begin() const { return ParameterList; }
   param_iterator param_end() const { return ParameterList + NumParameters; }
   unsigned getNumParams() const { return NumParameters; }
+  ArrayRef<IdentifierInfo *> params() {
+    return ArrayRef<IdentifierInfo *>(ParameterList, NumParameters);
+  }
   ArrayRef<const IdentifierInfo *> params() const {
-    return ArrayRef<const IdentifierInfo *>(ParameterList, NumParameters);
+    return const_cast<MacroInfo*>(this)->params();
   }
 
   /// Return the parameter number of the specified identifier,
@@ -250,6 +253,9 @@ class MacroInfo {
     return ReplacementTokens + NumReplacementTokens;
   }
   bool tokens_empty() const { return NumReplacementTokens == 0; }
+  MutableArrayRef<Token> tokens() {
+    return llvm::MutableArrayRef(ReplacementTokens, NumReplacementTokens);
+  }
   ArrayRef<Token> tokens() const {
     return llvm::ArrayRef(ReplacementTokens, NumReplacementTokens);
   }
@@ -293,10 +299,12 @@ class MacroInfo {
     assert(Depth != 0 && "Cannot enable not disabled macro");
     --Depth;
   }
-  // returns false if max recursion depth exceeded
-  [[nodiscard]] bool TryDisableMacro() {
+  enum : uint16_t { macro_recursion_depth_limit = 16'000 };
+  
+  [[nodiscard("infinite recursion check ignored")]]
+  bool TryDisableMacro() {
     assert((AllowRecurse || Depth == 0) && "Cannot disable an already-disabled macro!");
-    return ++Depth < recursion_depth_limit;
+    return ++Depth < macro_recursion_depth_limit;
   }
 
   /// Determine whether this macro was used for a header guard.
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index 575d08b83fd3a02..356be1d3b45cac9 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -160,6 +160,7 @@ class Preprocessor {
   IdentifierInfo *Ident__identifier;               // __identifier
   IdentifierInfo *Ident__VA_ARGS__;                // __VA_ARGS__
   IdentifierInfo *Ident__VA_OPT__;                 // __VA_OPT__
+  IdentifierInfo *Ident__THIS_MACRO__;             // __THIS_MACRO__
   IdentifierInfo *Ident__has_feature;              // __has_feature
   IdentifierInfo *Ident__has_extension;            // __has_extension
   IdentifierInfo *Ident__has_builtin;              // __has_builtin
@@ -2425,6 +2426,11 @@ class Preprocessor {
 private:
   friend void TokenLexer::ExpandFunctionArguments();
 
+  /// If macro definition containts __THIS_MACRO__ creates impl-only recursive
+  /// version of macro, and replaces all __THIS_MACRO__ tokens
+  /// with new created recusive version
+  void appendRecursiveVersionIfRequired(IdentifierInfo*, MacroInfo*);
+
   void PushIncludeMacroStack() {
     assert(CurLexerKind != CLK_CachingLexer && "cannot push a caching lexer");
     IncludeMacroStack.emplace_back(CurLexerKind, CurLexerSubmodule,
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 313475cfd0e113c..ca1f78280bfcb24 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -59,6 +59,34 @@
 
 using namespace clang;
 
+void Preprocessor::appendRecursiveVersionIfRequired(IdentifierInfo* II, MacroInfo* MI) {
+  if (!MI->isFunctionLike())
+    return;
+  auto is_this_macro_tok = [&] (const Token& t) {
+    return t.getKind() == tok::identifier && t.getIdentifierInfo() == Ident__THIS_MACRO__;
+  };
+  if (llvm::none_of(MI->tokens(), is_this_macro_tok))
+    return;
+  IdentifierInfo* ImplMacroII = [&] {
+    std::string ImplMacroName = "__THIS_MACRO__";
+    ImplMacroName += II->getName();
+    return getIdentifierInfo(ImplMacroName);
+  }();
+  MacroInfo* NewMI = AllocateMacroInfo(MI->getDefinitionLoc());
+  NewMI->setIsFunctionLike();
+  NewMI->setParameterList(MI->params(), getPreprocessorAllocator());
+  NewMI->setDefinitionEndLoc(MI->getDefinitionEndLoc());
+  if (MI->isC99Varargs()) NewMI->setIsC99Varargs();
+  if (MI->isGNUVarargs()) NewMI->setIsGNUVarargs();
+  for (auto& t : MI->tokens()) {
+    if (is_this_macro_tok(t))
+      t.setIdentifierInfo(ImplMacroII);
+  }
+  NewMI->setTokens(MI->tokens(), getPreprocessorAllocator());
+  NewMI->setAllowRecursive(true);
+  appendDefMacroDirective(ImplMacroII, NewMI);
+}
+
 MacroDirective *
 Preprocessor::getLocalMacroDirectiveHistory(const IdentifierInfo *II) const {
   if (!II->hadMacroDefinition())
@@ -91,6 +119,7 @@ void Preprocessor::appendMacroDirective(IdentifierInfo *II, MacroDirective *MD){
     II->setHasMacroDefinition(false);
   if (II->isFromAST())
     II->setChangedSinceDeserialization();
+  appendRecursiveVersionIfRequired(II, MD->getMacroInfo());
 }
 
 void Preprocessor::setLoadedMacroDirective(IdentifierInfo *II,
diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index f0381c18a8b6f77..4e6c0ce112d488e 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -121,6 +121,7 @@ Preprocessor::Preprocessor(std::shared_ptr<PreprocessorOptions> PPOpts,
   SetPoisonReason(Ident__VA_ARGS__,diag::ext_pp_bad_vaargs_use);
   (Ident__VA_OPT__ = getIdentifierInfo("__VA_OPT__"))->setIsPoisoned();
   SetPoisonReason(Ident__VA_OPT__,diag::ext_pp_bad_vaopt_use);
+  Ident__THIS_MACRO__ = getIdentifierInfo("__THIS_MACRO__");
 
   // Initialize the pragma handlers.
   RegisterBuiltinPragmas();
diff --git a/clang/test/Preprocessor/macro_infinite_recursion.cpp b/clang/test/Preprocessor/macro_infinite_recursion.cpp
index cac8e7abbec5af3..3306f468543bcb9 100644
--- a/clang/test/Preprocessor/macro_infinite_recursion.cpp
+++ b/clang/test/Preprocessor/macro_infinite_recursion.cpp
@@ -1,12 +1,12 @@
 // RUN: %clang_cc1 %s -Eonly -std=c++11 -pedantic -verify
 
-#define2 A A
+#define A() __THIS_MACRO__()
 
-A //expected-error {{macro recursion depth limit exceeded}}
+A() //expected-error {{macro recursion depth limit exceeded}}
 
 #undef A
 
-#define2 A(x) A(x)
+#define A(x) __THIS_MACRO__(x)
 
 A(5)  //expected-error {{macro recursion depth limit exceeded}}
 
diff --git a/clang/test/Preprocessor/macro_recursion.cpp b/clang/test/Preprocessor/macro_recursion.cpp
index cd415ce1a95e463..fc2c2ffd21eadd6 100644
--- a/clang/test/Preprocessor/macro_recursion.cpp
+++ b/clang/test/Preprocessor/macro_recursion.cpp
@@ -2,7 +2,7 @@
 
 #define merge_all_expand2(a, b) a ## b
 #define merge_all_expand(a, b) merge_all_expand2(a, b)
-#define2 concat_all(head, ...)merge_all_expand(head,__VA_OPT__(concat_all(__VA_ARGS__)))
+#define concat_all(head, ...)merge_all_expand(head,__VA_OPT__(__THIS_MACRO__(__VA_ARGS__)))
 0: concat_all(aa, bb, cc)
 1: [concat_all()]
 // CHECK: 0: aabbcc
@@ -12,7 +12,7 @@
 #undef merge_all_expand2
 #undef concat_all
 
-#define2 reverse(head, ...)__VA_OPT__(reverse(__VA_ARGS__),)head
+#define reverse(head, ...)__VA_OPT__(__THIS_MACRO__(__VA_ARGS__),)head
 
 2: reverse(1,2,3)
 
@@ -20,7 +20,7 @@
 
 #undef reverse
 
-#define2 fold_left(op, head, ...)(__VA_OPT__(fold_left(op,__VA_ARGS__)op)head)
+#define fold_left(op, head, ...)(__VA_OPT__(__THIS_MACRO__(op,__VA_ARGS__)op)head)
 
 3: fold_left(+, 1, 2, 3, 4)
 // CHECK: 3: ((((4)+3)+2)+1)

>From 1add34ebecc2fa45ed48c7a2156d8d080afcd8bf Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Sun, 24 Sep 2023 14:49:26 +0400
Subject: [PATCH 10/13] rm define2

---
 clang/include/clang/Basic/TokenKinds.def | 1 -
 clang/include/clang/Lex/MacroInfo.h      | 4 ++--
 clang/lib/Basic/IdentifierTable.cpp      | 2 --
 clang/lib/Format/WhitespaceManager.cpp   | 2 +-
 clang/lib/Lex/PPDirectives.cpp           | 7 +++----
 5 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/clang/include/clang/Basic/TokenKinds.def b/clang/include/clang/Basic/TokenKinds.def
index b227a6a5632f496..72e8df8c793a7b6 100644
--- a/clang/include/clang/Basic/TokenKinds.def
+++ b/clang/include/clang/Basic/TokenKinds.def
@@ -115,7 +115,6 @@ PPKEYWORD(__include_macros)
 
 // C99 6.10.3 - Macro Replacement.
 PPKEYWORD(define)
-PPKEYWORD(define2)
 PPKEYWORD(undef)
 
 // C99 6.10.4 - Line Control.
diff --git a/clang/include/clang/Lex/MacroInfo.h b/clang/include/clang/Lex/MacroInfo.h
index 8b91d33e971b752..49cbacf6df1acda 100644
--- a/clang/include/clang/Lex/MacroInfo.h
+++ b/clang/include/clang/Lex/MacroInfo.h
@@ -66,7 +66,7 @@ class MacroInfo {
   /// Length in characters of the macro definition.
   mutable unsigned DefinitionLength;
 
-  /// True if 'define2' used, enables expansion anyway
+  /// True only for inner-impl '__THIS_MACRO__', enables expansion anyway
   bool AllowRecurse : 1;
 
   mutable bool IsDefinitionLengthCached : 1;
@@ -118,7 +118,7 @@ class MacroInfo {
   enum : uint16_t { recursion_depth_limit = 16'000 };
   /// recursion depth,
   /// > 0 if we have started an expansion of this macro already.
-  /// for 'define' max is 1, for 'define2' max is depth limit
+  /// if !AllowRecurse max is 1, else max is recursion depth limit
   uint16_t Depth = 0;
 
   // Only the Preprocessor gets to create these.
diff --git a/clang/lib/Basic/IdentifierTable.cpp b/clang/lib/Basic/IdentifierTable.cpp
index 7300825ff6b826a..e5599d545541085 100644
--- a/clang/lib/Basic/IdentifierTable.cpp
+++ b/clang/lib/Basic/IdentifierTable.cpp
@@ -431,8 +431,6 @@ tok::PPKeywordKind IdentifierInfo::getPPKeywordID() const {
   unsigned Len = getLength();
   if (Len < 2) return tok::pp_not_keyword;
   const char *Name = getNameStart();
-  if (std::string_view(Name, Len) == "define2")
-    return tok::pp_define2;
   switch (HASH(Len, Name[0], Name[2])) {
   default: return tok::pp_not_keyword;
   CASE( 2, 'i', '\0', if);
diff --git a/clang/lib/Format/WhitespaceManager.cpp b/clang/lib/Format/WhitespaceManager.cpp
index d8ab76d6761553e..b7bd8d27dc976b1 100644
--- a/clang/lib/Format/WhitespaceManager.cpp
+++ b/clang/lib/Format/WhitespaceManager.cpp
@@ -743,7 +743,7 @@ void WhitespaceManager::alignConsecutiveMacros() {
     if (!Current || Current->isNot(tok::identifier))
       return false;
 
-    if (!Current->Previous || !Current->Previous->isOneOf(tok::pp_define, tok::pp_define2))
+    if (!Current->Previous || Current->Previous->isNot(tok::pp_define))
       return false;
 
     // For a macro function, 0 spaces are required between the
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 06b81985749aa25..9e4ce13bb9c32a9 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -1109,7 +1109,7 @@ class Preprocessor::ResetMacroExpansionHelper {
 void Preprocessor::HandleSkippedDirectiveWhileUsingPCH(Token &Result,
                                                        SourceLocation HashLoc) {
   if (const IdentifierInfo *II = Result.getIdentifierInfo()) {
-    if (II->getPPKeywordID() == tok::pp_define || II->getPPKeywordID() == tok::pp_define2) {
+    if (II->getPPKeywordID() == tok::pp_define) {
       return HandleDefineDirective(Result,
                                    /*ImmediatelyAfterHeaderGuard=*/false);
     }
@@ -1250,7 +1250,6 @@ void Preprocessor::HandleDirective(Token &Result) {
 
     // C99 6.10.3 - Macro Replacement.
     case tok::pp_define:
-    case tok::pp_define2:
       return HandleDefineDirective(Result, ImmediatelyAfterTopLevelIfndef);
     case tok::pp_undef:
       return HandleUndefDirective();
@@ -3037,7 +3036,7 @@ static bool isObjCProtectedMacro(const IdentifierInfo *II) {
          II->isStr("__unsafe_unretained") || II->isStr("__autoreleasing");
 }
 
-/// HandleDefineDirective - Implements \#define and define2. This consumes the entire macro
+/// HandleDefineDirective - Implements \#define. This consumes the entire macro
 /// line then lets the caller lex the next real token.
 void Preprocessor::HandleDefineDirective(
     Token &DefineTok, const bool ImmediatelyAfterHeaderGuard) {
@@ -3065,7 +3064,7 @@ void Preprocessor::HandleDefineDirective(
       MacroNameTok, ImmediatelyAfterHeaderGuard);
 
   if (!MI) return;
-  MI->setAllowRecursive(DefineTok.getIdentifierInfo()->getPPKeywordID() == tok::pp_define2);
+
   if (MacroShadowsKeyword &&
       !isConfigurationPattern(MacroNameTok, MI, getLangOpts())) {
     Diag(MacroNameTok, diag::warn_pp_macro_hides_keyword);

>From c879ca056bf9eb16fad28ad1d324bad829bfb7ca Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Sun, 24 Sep 2023 14:52:58 +0400
Subject: [PATCH 11/13] rm enum

---
 clang/include/clang/Lex/MacroInfo.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/clang/include/clang/Lex/MacroInfo.h b/clang/include/clang/Lex/MacroInfo.h
index 49cbacf6df1acda..e5b996115a96c2b 100644
--- a/clang/include/clang/Lex/MacroInfo.h
+++ b/clang/include/clang/Lex/MacroInfo.h
@@ -115,7 +115,7 @@ class MacroInfo {
   /// Whether this macro was used as header guard.
   bool UsedForHeaderGuard : 1;
 
-  enum : uint16_t { recursion_depth_limit = 16'000 };
+  enum : uint16_t { macro_recursion_depth_limit = 16'000 };
   /// recursion depth,
   /// > 0 if we have started an expansion of this macro already.
   /// if !AllowRecurse max is 1, else max is recursion depth limit
@@ -290,7 +290,7 @@ class MacroInfo {
   /// In other words, that we are not currently in an expansion of this macro.
   bool isEnabled() const {
     // macro disabled if depth exceeds and stops infinite recursion
-    return AllowRecurse ? Depth < recursion_depth_limit : Depth == 0;
+    return AllowRecurse ? Depth < macro_recursion_depth_limit : Depth == 0;
   }
   void setAllowRecursive(bool Allow) { AllowRecurse = Allow; }
   bool isAllowRecurse() const { return AllowRecurse; }
@@ -299,7 +299,6 @@ class MacroInfo {
     assert(Depth != 0 && "Cannot enable not disabled macro");
     --Depth;
   }
-  enum : uint16_t { macro_recursion_depth_limit = 16'000 };
   
   [[nodiscard("infinite recursion check ignored")]]
   bool TryDisableMacro() {

>From 998bf1306c0cc9c1f76a3e3eb6370036de2f7c18 Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Sun, 24 Sep 2023 15:08:31 +0400
Subject: [PATCH 12/13] comment fixes

---
 clang/include/clang/Lex/Preprocessor.h | 2 +-
 clang/lib/Lex/PPDirectives.cpp         | 2 +-
 clang/lib/Lex/PPMacroExpansion.cpp     | 2 --
 3 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index 356be1d3b45cac9..3a5bcac1de77427 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -2426,7 +2426,7 @@ class Preprocessor {
 private:
   friend void TokenLexer::ExpandFunctionArguments();
 
-  /// If macro definition containts __THIS_MACRO__ creates impl-only recursive
+  /// If macro definition contains __THIS_MACRO__ creates impl-only recursive
   /// version of macro, and replaces all __THIS_MACRO__ tokens
   /// with new created recusive version
   void appendRecursiveVersionIfRequired(IdentifierInfo*, MacroInfo*);
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 9e4ce13bb9c32a9..7edcb0577c2b25a 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -3036,7 +3036,7 @@ static bool isObjCProtectedMacro(const IdentifierInfo *II) {
          II->isStr("__unsafe_unretained") || II->isStr("__autoreleasing");
 }
 
-/// HandleDefineDirective - Implements \#define. This consumes the entire macro
+/// HandleDefineDirective - Implements \#define.  This consumes the entire macro
 /// line then lets the caller lex the next real token.
 void Preprocessor::HandleDefineDirective(
     Token &DefineTok, const bool ImmediatelyAfterHeaderGuard) {
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index ca1f78280bfcb24..6fbe08e3baa569a 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -643,8 +643,6 @@ bool Preprocessor::HandleMacroExpandedIdentifier(Token &Identifier,
     if (IdentifierInfo *NewII = Identifier.getIdentifierInfo()) {
       if (MacroInfo *NewMI = getMacroInfo(NewII))
         if (!NewMI->isEnabled() || NewMI == MI) {
-          if (NewMI->isAllowRecurse() && NewMI == MI)
-            Diag(Identifier, diag::err_pp_macro_recursion_depth_limit_exceeded);
           Identifier.setFlag(Token::DisableExpand);
           // Don't warn for "#define X X" like "#define bool bool" from
           // stdbool.h.

>From cab7a4a019af133cc84c465cc8edbed2205880ca Mon Sep 17 00:00:00 2001
From: Kelbon Nik <kelbonage at gmail.com>
Date: Sun, 24 Sep 2023 15:16:55 +0400
Subject: [PATCH 13/13] format

---
 clang/include/clang/Lex/MacroInfo.h    |  8 ++++----
 clang/include/clang/Lex/Preprocessor.h |  2 +-
 clang/lib/Lex/Lexer.cpp                |  2 +-
 clang/lib/Lex/MacroInfo.cpp            |  6 ++++--
 clang/lib/Lex/PPMacroExpansion.cpp     | 18 +++++++++++-------
 5 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/clang/include/clang/Lex/MacroInfo.h b/clang/include/clang/Lex/MacroInfo.h
index e5b996115a96c2b..b1df66961dd853d 100644
--- a/clang/include/clang/Lex/MacroInfo.h
+++ b/clang/include/clang/Lex/MacroInfo.h
@@ -190,7 +190,7 @@ class MacroInfo {
     return ArrayRef<IdentifierInfo *>(ParameterList, NumParameters);
   }
   ArrayRef<const IdentifierInfo *> params() const {
-    return const_cast<MacroInfo*>(this)->params();
+    return const_cast<MacroInfo *>(this)->params();
   }
 
   /// Return the parameter number of the specified identifier,
@@ -300,9 +300,9 @@ class MacroInfo {
     --Depth;
   }
   
-  [[nodiscard("infinite recursion check ignored")]]
-  bool TryDisableMacro() {
-    assert((AllowRecurse || Depth == 0) && "Cannot disable an already-disabled macro!");
+  [[nodiscard("infinite recursion check ignored")]] bool TryDisableMacro() {
+    assert((AllowRecurse || Depth == 0) &&
+            "Cannot disable an already-disabled macro!");
     return ++Depth < macro_recursion_depth_limit;
   }
 
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index 3a5bcac1de77427..fb128d8c0e77334 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -2429,7 +2429,7 @@ class Preprocessor {
   /// If macro definition contains __THIS_MACRO__ creates impl-only recursive
   /// version of macro, and replaces all __THIS_MACRO__ tokens
   /// with new created recusive version
-  void appendRecursiveVersionIfRequired(IdentifierInfo*, MacroInfo*);
+  void appendRecursiveVersionIfRequired(IdentifierInfo *, MacroInfo *);
 
   void PushIncludeMacroStack() {
     assert(CurLexerKind != CLK_CachingLexer && "cannot push a caching lexer");
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 178bcc08a72e208..70ba8f4f9c84fd6 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -847,7 +847,7 @@ bool Lexer::isAtEndOfMacroExpansion(SourceLocation loc,
                                     const SourceManager &SM,
                                     const LangOptions &LangOpts,
                                     SourceLocation *MacroEnd) {
-  for(SourceLocation expansionLoc; true;loc = expansionLoc) {
+  for (SourceLocation expansionLoc; true; loc = expansionLoc) {
     assert(loc.isValid() && loc.isMacroID() && "Expected a valid macro loc");
 
     SourceLocation spellLoc = SM.getSpellingLoc(loc);
diff --git a/clang/lib/Lex/MacroInfo.cpp b/clang/lib/Lex/MacroInfo.cpp
index 110e3232b66dc14..e042dd38a026311 100644
--- a/clang/lib/Lex/MacroInfo.cpp
+++ b/clang/lib/Lex/MacroInfo.cpp
@@ -155,9 +155,11 @@ LLVM_DUMP_METHOD void MacroInfo::dump() const {
   // FIXME: Dump locations.
   Out << "MacroInfo " << this;
   if (IsBuiltinMacro) Out << " builtin";
-  if (!isEnabled()) Out << " disabled";
+  if (!isEnabled())
+    Out << " disabled";
   if (IsUsed) Out << " used";
-  if (AllowRecurse) Out << " allow_recurse";
+  if (AllowRecurse)
+    Out << " allow_recurse";
   if (IsAllowRedefinitionsWithoutWarning)
     Out << " allow_redefinitions_without_warning";
   if (IsWarnIfUnused) Out << " warn_if_unused";
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 6fbe08e3baa569a..b02eedea137e800 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -59,26 +59,30 @@
 
 using namespace clang;
 
-void Preprocessor::appendRecursiveVersionIfRequired(IdentifierInfo* II, MacroInfo* MI) {
+void Preprocessor::appendRecursiveVersionIfRequired(IdentifierInfo *II,
+                                                    MacroInfo *MI) {
   if (!MI->isFunctionLike())
     return;
   auto is_this_macro_tok = [&] (const Token& t) {
-    return t.getKind() == tok::identifier && t.getIdentifierInfo() == Ident__THIS_MACRO__;
+    return t.getKind() == tok::identifier &&
+           t.getIdentifierInfo() == Ident__THIS_MACRO__;
   };
   if (llvm::none_of(MI->tokens(), is_this_macro_tok))
     return;
-  IdentifierInfo* ImplMacroII = [&] {
+  IdentifierInfo *ImplMacroII = [&] {
     std::string ImplMacroName = "__THIS_MACRO__";
     ImplMacroName += II->getName();
     return getIdentifierInfo(ImplMacroName);
   }();
-  MacroInfo* NewMI = AllocateMacroInfo(MI->getDefinitionLoc());
+  MacroInfo *NewMI = AllocateMacroInfo(MI->getDefinitionLoc());
   NewMI->setIsFunctionLike();
   NewMI->setParameterList(MI->params(), getPreprocessorAllocator());
   NewMI->setDefinitionEndLoc(MI->getDefinitionEndLoc());
-  if (MI->isC99Varargs()) NewMI->setIsC99Varargs();
-  if (MI->isGNUVarargs()) NewMI->setIsGNUVarargs();
-  for (auto& t : MI->tokens()) {
+  if (MI->isC99Varargs())
+    NewMI->setIsC99Varargs();
+  if (MI->isGNUVarargs())
+    NewMI->setIsGNUVarargs();
+  for (auto &t : MI->tokens()) {
     if (is_this_macro_tok(t))
       t.setIdentifierInfo(ImplMacroII);
   }



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