[clang-tidy] new check: bugprone-branch-clone

Summary:
Implement a check for detecting if/else if/else chains where two or more
branches are Type I clones of each other (that is, they contain identical code)
and for detecting switch statements where two or more consecutive branches are
Type I clones of each other.

Patch by donat.nagy.

Reviewers: alexfh, hokein, aaron.ballman, JonasToth

Reviewed By: JonasToth

Subscribers: MTC, lebedev.ri, whisperity, xazax.hun, Eugene.Zelenko, mgorny, rnkovacs, dkrupp, Szelethus, gamesh411, cfe-commits

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D54757

llvm-svn: 348343

diff --git a/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.cpp
new file mode 100644 (file)
index 0000000..f371231
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.cpp
@@ -0,0 +1,215 @@
+//===--- BranchCloneCheck.cpp - clang-tidy --------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "BranchCloneCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Analysis/CloneDetection.h"
+#include "llvm/Support/Casting.h"
+
+using namespace clang;
+using namespace clang::ast_matchers;
+
+/// Returns true when the statements are Type I clones of each other.
+static bool areStatementsIdentical(const Stmt *LHS, const Stmt *RHS,
+                                   const ASTContext &Context) {
+  llvm::FoldingSetNodeID DataLHS, DataRHS;
+  LHS->Profile(DataLHS, Context, false);
+  RHS->Profile(DataRHS, Context, false);
+  return (DataLHS == DataRHS);
+}
+
+namespace {
+/// A branch in a switch may consist of several statements; while a branch in
+/// an if/else if/else chain is one statement (which may be a CompoundStmt).
+using SwitchBranch = llvm::SmallVector<const Stmt *, 2>;
+} // anonymous namespace
+
+/// Determines if the bodies of two branches in a switch statements are Type I
+/// clones of each other. This function only examines the body of the branch
+/// and ignores the `case X:` or `default:` at the start of the branch.
+static bool areSwitchBranchesIdentical(const SwitchBranch LHS,
+                                       const SwitchBranch RHS,
+                                       const ASTContext &Context) {
+  if (LHS.size() != RHS.size())
+    return false;
+
+  for (size_t i = 0, Size = LHS.size(); i < Size; i++) {
+    // NOTE: We strip goto labels and annotations in addition to stripping
+    // the `case X:` or `default:` labels, but it is very unlikely that this
+    // would casue false positives in real-world code.
+    if (!areStatementsIdentical(LHS[i]->stripLabelLikeStatements(),
+                                RHS[i]->stripLabelLikeStatements(), Context)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+namespace clang {
+namespace tidy {
+namespace bugprone {
+
+void BranchCloneCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      ifStmt(stmt().bind("if"),
+             hasParent(stmt(unless(ifStmt(hasElse(equalsBoundNode("if")))))),
+             hasElse(stmt().bind("else"))),
+      this);
+  Finder->addMatcher(switchStmt().bind("switch"), this);
+  Finder->addMatcher(conditionalOperator().bind("condOp"), this);
+}
+
+void BranchCloneCheck::check(const MatchFinder::MatchResult &Result) {
+  const ASTContext &Context = *Result.Context;
+
+  if (const auto *IS = Result.Nodes.getNodeAs<IfStmt>("if")) {
+    const Stmt *Then = IS->getThen();
+    assert(Then && "An IfStmt must have a `then` branch!");
+
+    const Stmt *Else = Result.Nodes.getNodeAs<Stmt>("else");
+    assert(Else && "We only look for `if` statements with an `else` branch!");
+
+    if (!isa<IfStmt>(Else)) {
+      // Just a simple if with no `else if` branch.
+      if (areStatementsIdentical(Then->IgnoreContainers(),
+                                 Else->IgnoreContainers(), Context)) {
+        diag(IS->getBeginLoc(), "if with identical then and else branches");
+        diag(IS->getElseLoc(), "else branch starts here", DiagnosticIDs::Note);
+      }
+      return;
+    }
+
+    // This is the complicated case when we start an if/else if/else chain.
+    // To find all the duplicates, we collect all the branches into a vector.
+    llvm::SmallVector<const Stmt *, 4> Branches;
+    const IfStmt *Cur = IS;
+    while (true) {
+      // Store the `then` branch.
+      Branches.push_back(Cur->getThen());
+
+      Else = Cur->getElse();
+      // The chain ends if there is no `else` branch.
+      if (!Else)
+        break;
+
+      // Check if there is another `else if`...
+      Cur = dyn_cast<IfStmt>(Else);
+      if (!Cur) {
+        // ...this is just a plain `else` branch at the end of the chain.
+        Branches.push_back(Else);
+        break;
+      }
+    }
+
+    size_t N = Branches.size();
+    llvm::BitVector KnownAsClone(N);
+
+    for (size_t i = 0; i + 1 < N; i++) {
+      // We have already seen Branches[i] as a clone of an earlier branch.
+      if (KnownAsClone[i])
+        continue;
+
+      int NumCopies = 1;
+
+      for (size_t j = i + 1; j < N; j++) {
+        if (KnownAsClone[j] ||
+            !areStatementsIdentical(Branches[i]->IgnoreContainers(),
+                                    Branches[j]->IgnoreContainers(), Context))
+          continue;
+
+        NumCopies++;
+        KnownAsClone[j] = true;
+
+        if (NumCopies == 2) {
+          // We report the first occurence only when we find the second one.
+          diag(Branches[i]->getBeginLoc(),
+               "repeated branch in conditional chain");
+          diag(Lexer::getLocForEndOfToken(Branches[i]->getEndLoc(), 0,
+                                          *Result.SourceManager, getLangOpts()),
+               "end of the original", DiagnosticIDs::Note);
+        }
+
+        diag(Branches[j]->getBeginLoc(), "clone %0 starts here",
+             DiagnosticIDs::Note)
+            << (NumCopies - 1);
+      }
+    }
+    return;
+  }
+
+  if (const auto *CO = Result.Nodes.getNodeAs<ConditionalOperator>("condOp")) {
+    // We do not try to detect chains of ?: operators.
+    if (areStatementsIdentical(CO->getTrueExpr(), CO->getFalseExpr(), Context))
+      diag(CO->getQuestionLoc(),
+           "conditional operator with identical true and false expressions");
+
+    return;
+  }
+
+  if (const auto *SS = Result.Nodes.getNodeAs<SwitchStmt>("switch")) {
+    const CompoundStmt *Body = dyn_cast_or_null<CompoundStmt>(SS->getBody());
+
+    // Code like
+    //   switch (x) case 0: case 1: foobar();
+    // is legal and calls foobar() if and only if x is either 0 or 1;
+    // but we do not try to distinguish branches in such code.
+    if (!Body)
+      return;
+
+    // We will first collect the branches of the switch statements. For the
+    // sake of simplicity we say that branches are delimited by the SwitchCase
+    // (`case:` or `default:`) children of Body; that is, we ignore `case:` or
+    // `default:` labels embedded inside other statements and we do not follow
+    // the effects of `break` and other manipulation of the control-flow.
+    llvm::SmallVector<SwitchBranch, 4> Branches;
+    for (const Stmt *S : Body->body()) {
+      // If this is a `case` or `default`, we start a new, empty branch.
+      if (isa<SwitchCase>(S))
+        Branches.emplace_back();
+
+      // There may be code before the first branch (which can be dead code
+      // and can be code reached either through goto or through case labels
+      // that are embedded inside e.g. inner compound statements); we do not
+      // store those statements in branches.
+      if (!Branches.empty())
+        Branches.back().push_back(S);
+    }
+
+    auto End = Branches.end();
+    auto BeginCurrent = Branches.begin();
+    while (BeginCurrent < End) {
+      auto EndCurrent = BeginCurrent + 1;
+      while (EndCurrent < End &&
+             areSwitchBranchesIdentical(*BeginCurrent, *EndCurrent, Context)) {
+        ++EndCurrent;
+      }
+      // At this point the iterator range {BeginCurrent, EndCurrent} contains a
+      // complete family of consecutive identical branches.
+      if (EndCurrent > BeginCurrent + 1) {
+        diag(BeginCurrent->front()->getBeginLoc(),
+             "switch has %0 consecutive identical branches")
+            << static_cast<int>(std::distance(BeginCurrent, EndCurrent));
+        diag(Lexer::getLocForEndOfToken((EndCurrent - 1)->back()->getEndLoc(),
+                                        0, *Result.SourceManager,
+                                        getLangOpts()),
+             "last of these clones ends here", DiagnosticIDs::Note);
+      }
+      BeginCurrent = EndCurrent;
+    }
+    return;
+  }
+
+  llvm_unreachable("No if statement and no switch statement.");
+}
+
+} // namespace bugprone
+} // namespace tidy
+} // namespace clang

diff --git a/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.h b/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.h
new file mode 100644 (file)
index 0000000..4a3eadf
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/bugprone/BranchCloneCheck.h
@@ -0,0 +1,39 @@
+//===--- BranchCloneCheck.h - clang-tidy ------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_BRANCHCLONECHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_BRANCHCLONECHECK_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace bugprone {
+
+/// A check for detecting if/else if/else chains where two or more branches are
+/// Type I clones of each other (that is, they contain identical code), for
+/// detecting switch statements where two or more consecutive branches are
+/// Type I clones of each other, and for detecting conditional operators where
+/// the true and false expressions are Type I clones of each other.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/bugprone-branch-clone.html
+class BranchCloneCheck : public ClangTidyCheck {
+public:
+  BranchCloneCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace bugprone
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_BRANCHCLONECHECK_H

diff --git a/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp b/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
index beb58f5..963b2e8 100644 (file)
--- a/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
@@ -14,6 +14,7 @@
 #include "ArgumentCommentCheck.h"
 #include "AssertSideEffectCheck.h"
 #include "BoolPointerImplicitConversionCheck.h"
+#include "BranchCloneCheck.h"
 #include "CopyConstructorInitCheck.h"
 #include "DanglingHandleCheck.h"
 #include "ExceptionEscapeCheck.h"
@@ -65,6 +66,8 @@ public:
         "bugprone-assert-side-effect");
     CheckFactories.registerCheck<BoolPointerImplicitConversionCheck>(
         "bugprone-bool-pointer-implicit-conversion");
+    CheckFactories.registerCheck<BranchCloneCheck>(
+        "bugprone-branch-clone");
     CheckFactories.registerCheck<CopyConstructorInitCheck>(
         "bugprone-copy-constructor-init");
     CheckFactories.registerCheck<DanglingHandleCheck>(

diff --git a/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt b/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
index a8c64b7..66f1faf 100644 (file)
--- a/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
+++ b/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
@@ -4,6 +4,7 @@ add_clang_library(clangTidyBugproneModule
   ArgumentCommentCheck.cpp
   AssertSideEffectCheck.cpp
   BoolPointerImplicitConversionCheck.cpp
+  BranchCloneCheck.cpp
   BugproneTidyModule.cpp
   CopyConstructorInitCheck.cpp
   DanglingHandleCheck.cpp

diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index cec9645..3857304 100644 (file)
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -122,6 +122,13 @@ Improvements to clang-tidy
   Flags uses of ``absl::StrCat()`` to append to a ``std::string``. Suggests
   ``absl::StrAppend()`` should be used instead.
 
+- New :doc:`bugprone-branch-clone
+  <clang-tidy/checks/bugprone-branch-clone>` check.
+
+  Checks for repeated branches in ``if/else if/else`` chains, consecutive
+  repeated branches in ``switch`` statements and indentical true and false
+  branches in conditional operators.
+
 - New :doc:`bugprone-too-small-loop-variable
   <clang-tidy/checks/bugprone-too-small-loop-variable>` check.
 

diff --git a/clang-tools-extra/docs/clang-tidy/checks/bugprone-branch-clone.rst b/clang-tools-extra/docs/clang-tidy/checks/bugprone-branch-clone.rst
new file mode 100644 (file)
index 0000000..b4c07b4
--- /dev/null
+++ b/clang-tools-extra/docs/clang-tidy/checks/bugprone-branch-clone.rst
@@ -0,0 +1,90 @@
+.. title:: clang-tidy - bugprone-branch-clone
+
+bugprone-branch-clone
+=====================
+
+Checks for repeated branches in ``if/else if/else`` chains, consecutive
+repeated branches in ``switch`` statements and indentical true and false
+branches in conditional operators.
+
+.. code-block:: c++
+
+    if (test_value(x)) {
+      y++;
+      do_something(x, y);
+    } else {
+      y++;
+      do_something(x, y);
+    }
+
+In this simple example (which could arise e.g. as a copy-paste error) the
+``then`` and ``else`` branches are identical and the code is equivalent the
+following shorter and cleaner code:
+
+.. code-block:: c++
+
+    test_value(x); // can be omitted unless it has side effects
+    y++;
+    do_something(x, y);
+
+
+If this is the inteded behavior, then there is no reason to use a conditional
+statement; otherwise the issue can be solved by fixing the branch that is
+handled incorrectly.
+
+The check also detects repeated branches in longer ``if/else if/else`` chains
+where it would be even harder to notice the problem.
+
+In ``switch`` statements the check only reports repeated branches when they are
+consecutive, because it is relatively common that the ``case:`` labels have
+some natural ordering and rearranging them would decrease the readability of
+the code. For example:
+
+.. code-block:: c++
+
+    switch (ch) {
+    case 'a':
+      return 10;
+    case 'A':
+      return 10;
+    case 'b':
+      return 11;
+    case 'B':
+      return 11;
+    default:
+      return 10;
+    }
+
+Here the check reports that the ``'a'`` and ``'A'`` branches are identical
+(and that the ``'b'`` and ``'B'`` branches are also identical), but does not
+report that the ``default:`` branch is also idenical to the first two branches.
+If this is indeed the correct behavior, then it could be implemented as:
+
+.. code-block:: c++
+
+    switch (ch) {
+    case 'a':
+    case 'A':
+      return 10;
+    case 'b':
+    case 'B':
+      return 11;
+    default:
+      return 10;
+    }
+
+Here the check does not warn for the repeated ``return 10;``, which is good if
+we want to preserve that ``'a'`` is before ``'b'`` and ``default:`` is the last
+branch.
+
+Finally, the check also examines conditional operators and reports code like:
+
+.. code-block:: c++
+
+    return test_value(x) ? x : x;
+
+Unlike if statements, the check does not detect chains of conditional
+operators.
+
+Note: This check also reports situations where branches become identical only
+after preprocession.

diff --git a/clang-tools-extra/docs/clang-tidy/checks/list.rst b/clang-tools-extra/docs/clang-tidy/checks/list.rst
index e3528ae..7b810f5 100644 (file)
--- a/clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/list.rst
@@ -31,6 +31,7 @@ Clang-Tidy Checks
    bugprone-argument-comment
    bugprone-assert-side-effect
    bugprone-bool-pointer-implicit-conversion
+   bugprone-branch-clone
    bugprone-copy-constructor-init
    bugprone-dangling-handle
    bugprone-exception-escape

diff --git a/clang-tools-extra/test/clang-tidy/bugprone-branch-clone.cpp b/clang-tools-extra/test/clang-tidy/bugprone-branch-clone.cpp
new file mode 100644 (file)
index 0000000..8caa917
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/bugprone-branch-clone.cpp
@@ -0,0 +1,1017 @@
+// RUN: %check_clang_tidy %s bugprone-branch-clone %t
+
+void test_basic1(int in, int &out) {
+  if (in > 77)
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    out++;
+  else
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+    out++;
+
+  out++;
+}
+
+void test_basic2(int in, int &out) {
+  if (in > 77) {
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    out++;
+  }
+  else {
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+    out++;
+  }
+
+  out++;
+}
+
+void test_basic3(int in, int &out) {
+  if (in > 77) {
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    out++;
+  }
+  else
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+    out++;
+
+  out++;
+}
+
+void test_basic4(int in, int &out) {
+  if (in > 77) {
+    out--;
+  }
+  else {
+    out++;
+  }
+}
+
+void test_basic5(int in, int &out) {
+  if (in > 77) {
+    out++;
+  }
+  else {
+    out++;
+    out++;
+  }
+}
+
+void test_basic6(int in, int &out) {
+  if (in > 77) {
+    out++;
+  }
+  else {
+    out++, out++;
+  }
+}
+
+void test_basic7(int in, int &out) {
+  if (in > 77) {
+    out++;
+    out++;
+  }
+  else
+    out++;
+
+  out++;
+}
+
+void test_basic8(int in, int &out) {
+  if (in > 77) {
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    out++;
+    out++;
+  } else {
+// CHECK-MESSAGES: :[[@LINE-1]]:5: note: else branch starts here
+    out++;
+    out++;
+  }
+
+  if (in % 2)
+    out++;
+}
+
+void test_basic9(int in, int &out) {
+  if (in > 77) {
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    if (in % 2)
+      out++;
+    else
+      out--;
+  } else {
+// CHECK-MESSAGES: :[[@LINE-1]]:5: note: else branch starts here
+    if (in % 2)
+      out++;
+    else
+      out--;
+  }
+}
+
+// If we remove the braces from the previous example, the check recognizes it
+// as an `else if`.
+void test_basic10(int in, int &out) {
+  if (in > 77)
+    if (in % 2)
+      out++;
+    else
+      out--;
+  else
+    if (in % 2)
+      out++;
+    else
+      out--;
+
+}
+
+void test_basic11(int in, int &out) {
+  if (in > 77) {
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    if (in % 2)
+      out++;
+    else
+      out--;
+    if (in % 3)
+      out++;
+    else
+      out--;
+  } else {
+// CHECK-MESSAGES: :[[@LINE-1]]:5: note: else branch starts here
+    if (in % 2)
+      out++;
+    else
+      out--;
+    if (in % 3)
+      out++;
+    else
+      out--;
+  }
+}
+
+void test_basic12(int in, int &out) {
+  if (in > 77) {
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+  } else {
+// CHECK-MESSAGES: :[[@LINE-1]]:5: note: else branch starts here
+  }
+}
+
+void test_basic13(int in, int &out) {
+  if (in > 77) {
+    // Empty compound statement is not identical to null statement.
+  } else;
+}
+
+// We use a comparison that ignores redundant parentheses:
+void test_basic14(int in, int &out) {
+  if (in > 77)
+    out += 2;
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+  else
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+    (out) += (2);
+}
+
+void test_basic15(int in, int &out) {
+  if (in > 77)
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    ((out += 2));
+  else
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+    out += 2;
+}
+
+// ..but does not apply additional simplifications: 
+void test_basic16(int in, int &out) {
+  if (in > 77)
+    out += 2;
+  else
+    out += 1 + 1;
+}
+
+// ..and does not forget important parentheses:
+int test_basic17(int a, int b, int c, int mode) {
+  if (mode>8)
+    return (a + b) * c;
+  else
+    return a + b * c;
+}
+
+//=========--------------------==========//
+
+#define PASTE_CODE(x) x
+
+void test_macro1(int in, int &out) {
+  PASTE_CODE(
+    if (in > 77)
+// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: if with identical then and else branches [bugprone-branch-clone]
+      out++;
+    else
+// CHECK-MESSAGES: :[[@LINE-1]]:5: note: else branch starts here
+      out++;
+  )
+
+  out--;
+}
+
+void test_macro2(int in, int &out) {
+  PASTE_CODE(
+    if (in > 77)
+// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: if with identical then and else branches [bugprone-branch-clone]
+      out++;
+  )
+  else
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+    out++;
+}
+
+void test_macro3(int in, int &out) {
+  if (in > 77)
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    out++;
+  PASTE_CODE(
+    else
+// CHECK-MESSAGES: :[[@LINE-1]]:5: note: else branch starts here
+      out++;
+  )
+}
+
+void test_macro4(int in, int &out) {
+  if (in > 77)
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    out++;
+  else
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+    PASTE_CODE(
+      out++;
+    )
+}
+
+void test_macro5(int in, int &out) {
+  PASTE_CODE(if) (in > 77)
+// CHECK-MESSAGES: :[[@LINE-1]]:14: warning: if with identical then and else branches [bugprone-branch-clone]
+    out++;
+  PASTE_CODE(else)
+// CHECK-MESSAGES: :[[@LINE-1]]:14: note: else branch starts here
+    out++;
+}
+
+#define OTHERWISE_INCREASE else out++
+
+void test_macro6(int in, int &out) {
+  if (in > 77)
+      out++;
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+  OTHERWISE_INCREASE;
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+// CHECK-MESSAGES: :[[@LINE-8]]:28: note: expanded from macro 'OTHERWISE_INCREASE'
+}
+
+#define COND_INCR(a, b, c) \
+  do {                     \
+    if ((a))               \
+      (b)++;               \
+    else                   \ 
+      (c)++;               \
+  } while (0)
+
+void test_macro7(int in, int &out1, int &out2) {
+  COND_INCR(in, out1, out1);
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE-9]]:5: note: expanded from macro 'COND_INCR'
+// CHECK-MESSAGES: :[[@LINE-3]]:3: note: else branch starts here
+// CHECK-MESSAGES: :[[@LINE-8]]:5: note: expanded from macro 'COND_INCR'
+}
+
+void test_macro8(int in, int &out1, int &out2) {
+  COND_INCR(in, out1, out2);
+}
+
+void test_macro9(int in, int &out1, int &out2) {
+  COND_INCR(in, out2, out2);
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE-21]]:5: note: expanded from macro 'COND_INCR'
+// CHECK-MESSAGES: :[[@LINE-3]]:3: note: else branch starts here
+// CHECK-MESSAGES: :[[@LINE-20]]:5: note: expanded from macro 'COND_INCR'
+}
+
+#define CONCAT(a, b) a##b
+
+void test_macro10(int in, int &out) {
+  CONCAT(i, f) (in > 77)
+// CHECK-MESSAGES: :[[@LINE-1]]:10: warning: if with identical then and else branches [bugprone-branch-clone]
+    out++;
+  CONCAT(el, se)
+// CHECK-MESSAGES: :[[@LINE-1]]:10: note: else branch starts here
+    out++;
+}
+
+#define PROBLEM (-1)
+
+int test_macro11(int count) {
+  if (!count)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: warning: repeated branch in conditional chain [bugprone-branch-clone]
+    return PROBLEM;
+// CHECK-MESSAGES: :[[@LINE-1]]:10: note: end of the original
+  else if (count == 13)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: clone 1 starts here
+    return -1;
+  else
+    return count * 2;
+}
+
+#define IF if (
+#define THEN ) {
+#define ELSE } else {
+#define END }
+
+void test_macro12(int in, int &out) {
+  IF in > 77 THEN
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE-8]]:12: note: expanded from macro 'IF'
+    out++;
+    out++;
+  ELSE
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+// CHECK-MESSAGES: :[[@LINE-12]]:14: note: expanded from macro 'IF'
+    out++;
+    out++;
+  END
+}
+
+// A hack for implementing a switch with no fallthrough:
+#define SWITCH(x) switch (x) {
+#define CASE(x) break; case (x):
+#define DEFAULT break; default:
+
+void test_macro13(int in, int &out) {
+  SWITCH(in)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE-6]]:24: note: expanded from macro 'CASE'
+    CASE(1)
+      out++;
+      out++;
+    CASE(2)
+      out++;
+      out++;
+    CASE(3)
+      out++;
+      out++;
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: last of these clones ends here
+// CHECK-MESSAGES: :[[@LINE-17]]:22: note: expanded from macro 'CASE'
+    CASE(4)
+      out++;
+    CASE(5)
+// CHECK-MESSAGES: :[[@LINE+1]]:3: warning: switch has 2 consecutive identical branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE-22]]:24: note: expanded from macro 'CASE'
+    CASE(6)
+      out--;
+    CASE(7)
+      out--;
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: last of these clones ends here
+// CHECK-MESSAGES: :[[@LINE-28]]:22: note: expanded from macro 'CASE'
+// CHECK-MESSAGES: :[[@LINE+1]]:3: warning: switch has 2 consecutive identical branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE-30]]:24: note: expanded from macro 'CASE'
+    CASE(8)
+      out++;
+      out++;
+    CASE(9)
+      out++;
+      out++;
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: last of these clones ends here
+// CHECK-MESSAGES: :[[@LINE-37]]:22: note: expanded from macro 'DEFAULT'
+// CHECK-MESSAGES: :[[@LINE+1]]:3: warning: switch has 2 consecutive identical branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE-39]]:24: note: expanded from macro 'DEFAULT'
+    DEFAULT
+      out--;
+      out--;
+    CASE(10)
+      out--;
+      out--;
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: last of these clones ends here
+// CHECK-MESSAGES: :[[@LINE-48]]:22: note: expanded from macro 'CASE'
+    CASE(12)
+      out++;
+    CASE(13)
+      out++;
+  END
+}
+
+//=========--------------------==========//
+
+void test_chain1(int in, int &out) {
+  if (in > 77)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: warning: repeated branch in conditional chain [bugprone-branch-clone]
+    out++;
+// CHECK-MESSAGES: :[[@LINE-1]]:10: note: end of the original
+  else if (in > 55)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: clone 1 starts here
+    out++;
+
+  out++;
+}
+
+void test_chain2(int in, int &out) {
+  if (in > 77)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: warning: repeated branch in conditional chain [bugprone-branch-clone]
+    out++;
+// CHECK-MESSAGES: :[[@LINE-1]]:10: note: end of the original
+  else if (in > 55)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: clone 1 starts here
+    out++;
+  else if (in > 42)
+    out--;
+  else if (in > 28)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: clone 2 starts here
+    out++;
+  else if (in > 12) {
+    out++;
+    out *= 7;
+  } else if (in > 7) {
+// CHECK-MESSAGES: :[[@LINE-1]]:22: note: clone 3 starts here
+    out++;
+  }
+}
+
+void test_chain3(int in, int &out) {
+  if (in > 77) {
+// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: repeated branch in conditional chain [bugprone-branch-clone]
+    out++;
+    out++;
+// CHECK-MESSAGES: :[[@LINE+1]]:4: note: end of the original
+  } else if (in > 55) {
+// CHECK-MESSAGES: :[[@LINE-1]]:23: note: clone 1 starts here
+    out++;
+    out++;
+  } else if (in > 42)
+    out--;
+  else if (in > 28) {
+// CHECK-MESSAGES: :[[@LINE-1]]:21: note: clone 2 starts here
+    out++;
+    out++;
+  } else if (in > 12) {
+    out++;
+    out++;
+    out++;
+    out *= 7;
+  } else if (in > 7) {
+// CHECK-MESSAGES: :[[@LINE-1]]:22: note: clone 3 starts here
+    out++;
+    out++;
+  }
+}
+
+// In this chain there are two clone families; notice that the checker
+// describes all branches of the first one before mentioning the second one.
+void test_chain4(int in, int &out) {
+  if (in > 77) {
+// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: repeated branch in conditional chain [bugprone-branch-clone]
+    out++;
+    out++;
+// CHECK-MESSAGES: :[[@LINE+1]]:4: note: end of the original
+  } else if (in > 55) {
+// CHECK-MESSAGES: :[[@LINE-1]]:23: note: clone 1 starts here
+// CHECK-MESSAGES: :[[@LINE+8]]:21: note: clone 2 starts here
+// CHECK-MESSAGES: :[[@LINE+15]]:22: note: clone 3 starts here
+    out++;
+    out++;
+  } else if (in > 42)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: warning: repeated branch in conditional chain [bugprone-branch-clone]
+    out--;
+// CHECK-MESSAGES: :[[@LINE-1]]:10: note: end of the original
+  else if (in > 28) {
+    out++;
+    out++;
+  } else if (in > 12) {
+    out++;
+    out++;
+    out++;
+    out *= 7;
+  } else if (in > 7) {
+    out++;
+    out++;
+  } else if (in > -3) {
+// CHECK-MESSAGES: :[[@LINE-1]]:23: note: clone 1 starts here
+    out--;
+  }
+}
+
+void test_chain5(int in, int &out) {
+  if (in > 77)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: warning: repeated branch in conditional chain [bugprone-branch-clone]
+    out++;
+// CHECK-MESSAGES: :[[@LINE-1]]:10: note: end of the original
+  else if (in > 55)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: clone 1 starts here
+    out++;
+  else if (in > 42)
+    out--;
+  else if (in > 28)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: clone 2 starts here
+    out++;
+  else if (in > 12) {
+    out++;
+    out *= 7;
+  } else {
+// CHECK-MESSAGES: :[[@LINE-1]]:10: note: clone 3 starts here
+    out++;
+  }
+}
+
+void test_chain6(int in, int &out) {
+  if (in > 77) {
+// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: repeated branch in conditional chain [bugprone-branch-clone]
+    out++;
+    out++;
+// CHECK-MESSAGES: :[[@LINE+1]]:4: note: end of the original
+  } else if (in > 55) {
+// CHECK-MESSAGES: :[[@LINE-1]]:23: note: clone 1 starts here
+    out++;
+    out++;
+  } else if (in > 42)
+    out--;
+  else if (in > 28) {
+// CHECK-MESSAGES: :[[@LINE-1]]:21: note: clone 2 starts here
+    out++;
+    out++;
+  } else if (in > 12) {
+    out++;
+    out++;
+    out++;
+    out *= 7;
+  } else {
+// CHECK-MESSAGES: :[[@LINE-1]]:10: note: clone 3 starts here
+    out++;
+    out++;
+  }
+}
+
+void test_nested(int a, int b, int c, int &out) {
+  if (a > 5) {
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE+27]]:5: note: else branch starts here
+    if (b > 5) {
+// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: repeated branch in conditional chain [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE+9]]:6: note: end of the original
+// CHECK-MESSAGES: :[[@LINE+8]]:24: note: clone 1 starts here
+// CHECK-MESSAGES: :[[@LINE+14]]:12: note: clone 2 starts here
+      if (c > 5)
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: if with identical then and else branches [bugprone-branch-clone]
+        out++;
+      else
+// CHECK-MESSAGES: :[[@LINE-1]]:7: note: else branch starts here
+        out++;
+    } else if (b > 15) {
+      if (c > 5)
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: if with identical then and else branches [bugprone-branch-clone]
+        out++;
+      else
+// CHECK-MESSAGES: :[[@LINE-1]]:7: note: else branch starts here
+        out++;
+    } else {
+      if (c > 5)
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: if with identical then and else branches [bugprone-branch-clone]
+        out++;
+      else
+// CHECK-MESSAGES: :[[@LINE-1]]:7: note: else branch starts here
+        out++;
+    }
+  } else {
+    if (b > 5) {
+// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: repeated branch in conditional chain [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE+9]]:6: note: end of the original
+// CHECK-MESSAGES: :[[@LINE+8]]:24: note: clone 1 starts here
+// CHECK-MESSAGES: :[[@LINE+14]]:12: note: clone 2 starts here
+      if (c > 5)
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: if with identical then and else branches [bugprone-branch-clone]
+        out++;
+      else
+// CHECK-MESSAGES: :[[@LINE-1]]:7: note: else branch starts here
+        out++;
+    } else if (b > 15) {
+      if (c > 5)
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: if with identical then and else branches [bugprone-branch-clone]
+        out++;
+      else
+// CHECK-MESSAGES: :[[@LINE-1]]:7: note: else branch starts here
+        out++;
+    } else {
+      if (c > 5)
+// CHECK-MESSAGES: :[[@LINE-1]]:7: warning: if with identical then and else branches [bugprone-branch-clone]
+        out++;
+      else
+// CHECK-MESSAGES: :[[@LINE-1]]:7: note: else branch starts here
+        out++;
+    }
+  }
+}
+
+//=========--------------------==========//
+
+template <class T>
+void test_template_not_instantiated(const T &t) {
+  int a;
+  if (t)
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    a++;
+  else
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+    a++;
+}
+
+template <class T>
+void test_template_instantiated(const T &t) {
+  int a;
+  if (t)
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    a++;
+  else
+// CHECK-MESSAGES: :[[@LINE-1]]:3: note: else branch starts here
+    a++;
+}
+
+template void test_template_instantiated<int>(const int &t);
+
+template <class T>
+void test_template2(T t, int a) {
+  if (a) {
+    T b(0);
+    a += b;
+  } else {
+    int b(0);
+    a += b;
+  }
+}
+
+template void test_template2<int>(int t, int a);
+
+template <class T>
+void test_template3(T t, int a) {
+  if (a) {
+    T b(0);
+    a += b;
+  } else {
+    int b(0);
+    a += b;
+  }
+}
+
+template void test_template3<short>(short t, int a);
+
+template <class T>
+void test_template_two_instances(T t, int &a) {
+  if (a) {
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    a += int(t);
+  } else {
+// CHECK-MESSAGES: :[[@LINE-1]]:5: note: else branch starts here
+    a += int(t);
+  }
+}
+
+template void test_template_two_instances<short>(short t, int &a);
+template void test_template_two_instances<long>(long t, int &a);
+
+class C {
+  int member;
+  void inline_method(int arg) {
+    if (arg)
+// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: if with identical then and else branches [bugprone-branch-clone]
+      member = 3;
+    else
+// CHECK-MESSAGES: :[[@LINE-1]]:5: note: else branch starts here
+      member = 3;
+  }
+  int other_method();
+};
+
+int C::other_method() {
+  if (member) {
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: if with identical then and else branches [bugprone-branch-clone]
+    return 8;
+  } else {
+// CHECK-MESSAGES: :[[@LINE-1]]:5: note: else branch starts here
+    return 8;
+  }
+}
+
+//=========--------------------==========//
+
+int simple_switch(char ch) {
+  switch (ch) {
+// CHECK-MESSAGES: :[[@LINE+1]]:3: warning: switch has 2 consecutive identical branches [bugprone-branch-clone]
+  case 'a':
+    return 10;
+  case 'A':
+    return 10;
+// CHECK-MESSAGES: :[[@LINE-1]]:14: note: last of these clones ends here
+// CHECK-MESSAGES: :[[@LINE+1]]:3: warning: switch has 2 consecutive identical branches [bugprone-branch-clone]
+  case 'b':
+    return 11;
+  case 'B':
+    return 11;
+// CHECK-MESSAGES: :[[@LINE-1]]:14: note: last of these clones ends here
+// CHECK-MESSAGES: :[[@LINE+1]]:3: warning: switch has 2 consecutive identical branches [bugprone-branch-clone]
+  case 'c':
+    return 10;
+  case 'C':
+    return 10;
+// CHECK-MESSAGES: :[[@LINE-1]]:14: note: last of these clones ends here
+  default:
+    return 0;
+  }
+}
+
+int long_sequence_switch(char ch) {
+  switch (ch) {
+// CHECK-MESSAGES: :[[@LINE+1]]:3: warning: switch has 7 consecutive identical branches [bugprone-branch-clone]
+  case 'a':
+    return 10;
+  case 'A':
+    return 10;
+  case 'b':
+    return 10;
+  case 'B':
+    return 10;
+  case 'c':
+    return 10;
+  case 'C':
+    return 10;
+  default:
+    return 10;
+// CHECK-MESSAGES: :[[@LINE-1]]:14: note: last of these clones ends here
+  }
+}
+
+int nested_switch(int a, int b, int c) {
+  switch (a) {
+// CHECK-MESSAGES: :[[@LINE+2]]:3: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE+114]]:6: note: last of these clones ends here
+  case 1:
+    switch (b) {
+// CHECK-MESSAGES: :[[@LINE+2]]:5: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE+33]]:8: note: last of these clones ends here
+    case 1:
+      switch (c) {
+// CHECK-MESSAGES: :[[@LINE+1]]:7: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+      case 1:
+        return 42;
+      case 2:
+        return 42;
+      default:
+        return 42;
+// CHECK-MESSAGES: :[[@LINE-1]]:18: note: last of these clones ends here
+      }
+    case 2:
+      switch (c) {
+// CHECK-MESSAGES: :[[@LINE+1]]:7: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+      case 1:
+        return 42;
+      case 2:
+        return 42;
+      default:
+        return 42;
+// CHECK-MESSAGES: :[[@LINE-1]]:18: note: last of these clones ends here
+      }
+    default:
+      switch (c) {
+// CHECK-MESSAGES: :[[@LINE+1]]:7: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+      case 1:
+        return 42;
+      case 2:
+        return 42;
+      default:
+        return 42;
+// CHECK-MESSAGES: :[[@LINE-1]]:18: note: last of these clones ends here
+      }
+    }
+  case 2:
+    switch (b) {
+// CHECK-MESSAGES: :[[@LINE+2]]:5: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE+33]]:8: note: last of these clones ends here
+    case 1:
+      switch (c) {
+// CHECK-MESSAGES: :[[@LINE+1]]:7: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+      case 1:
+        return 42;
+      case 2:
+        return 42;
+      default:
+        return 42;
+// CHECK-MESSAGES: :[[@LINE-1]]:18: note: last of these clones ends here
+      }
+    case 2:
+      switch (c) {
+// CHECK-MESSAGES: :[[@LINE+1]]:7: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+      case 1:
+        return 42;
+      case 2:
+        return 42;
+      default:
+        return 42;
+// CHECK-MESSAGES: :[[@LINE-1]]:18: note: last of these clones ends here
+      }
+    default:
+      switch (c) {
+// CHECK-MESSAGES: :[[@LINE+1]]:7: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+      case 1:
+        return 42;
+      case 2:
+        return 42;
+      default:
+        return 42;
+// CHECK-MESSAGES: :[[@LINE-1]]:18: note: last of these clones ends here
+      }
+    }
+  default:
+    switch (b) {
+// CHECK-MESSAGES: :[[@LINE+2]]:5: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+// CHECK-MESSAGES: :[[@LINE+33]]:8: note: last of these clones ends here
+    case 1:
+      switch (c) {
+// CHECK-MESSAGES: :[[@LINE+1]]:7: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+      case 1:
+        return 42;
+      case 2:
+        return 42;
+      default:
+        return 42;
+// CHECK-MESSAGES: :[[@LINE-1]]:18: note: last of these clones ends here
+      }
+    case 2:
+      switch (c) {
+// CHECK-MESSAGES: :[[@LINE+1]]:7: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+      case 1:
+        return 42;
+      case 2:
+        return 42;
+      default:
+        return 42;
+// CHECK-MESSAGES: :[[@LINE-1]]:18: note: last of these clones ends here
+      }
+    default:
+      switch (c) {
+// CHECK-MESSAGES: :[[@LINE+1]]:7: warning: switch has 3 consecutive identical branches [bugprone-branch-clone]
+      case 1:
+        return 42;
+      case 2:
+        return 42;
+      default:
+        return 42;
+// CHECK-MESSAGES: :[[@LINE-1]]:18: note: last of these clones ends here
+      }
+    }
+  }
+}
+
+//=========--------------------==========//
+
+// This should not produce warnings, as in switch statements we only report
+// identical branches when they are consecutive. Also note that a branch
+// terminated by a break is different from a branch terminated by the end of
+// the switch statement.
+int interleaved_cases(int a, int b) {
+  switch (a) {
+  case 3:
+  case 4:
+    b = 2;
+    break;
+  case 5:
+    b = 3;
+    break;
+  case 6:
+    b = 2;
+    break;
+  case 7:
+    if (b % 2) {
+      b++;
+    } else {
+      b++;
+      break;
+    }
+    b = 2;
+    break;
+  case 8:
+    b = 2;
+  case 9:
+    b = 3;
+    break;
+  default:
+    b = 3;
+  }
+  return b;
+}
+
+
+// A case: or default: is only considered to be the start of a branch if it is a direct child of the CompoundStmt forming the body of the switch
+int buried_cases(int foo) {
+  switch (foo) {
+    {
+    case 36:
+      return 8;
+    default:
+      return 8;
+    }
+  }
+}
+
+// Here the `case 7:` is a child statement of the GotoLabelStmt, so the checker
+// thinks that it is part of the `case 9:` branch. While this result is
+// counterintuitve, mixing goto labels and switch statements in this fashion is
+// pretty rare, so it does not deserve a special case in the checker code.
+int decorated_cases(int z) {
+  if (!(z % 777)) {
+    goto lucky;
+  }
+  switch (z) {
+// CHECK-MESSAGES: :[[@LINE+1]]:3: warning: switch has 2 consecutive identical branches [bugprone-branch-clone]
+  case 1:
+  case 2:
+  case 3:
+    z++;
+    break;
+  case 4:
+  case 5:
+    z++;
+    break;
+// CHECK-MESSAGES: :[[@LINE-1]]:10: note: last of these clones ends here
+  case 9:
+    z++;
+    break;
+  lucky:
+  case 7:
+    z += 3;
+    z *= 2;
+    break;
+  case 92:
+    z += 3;
+    z *= 2;
+    break;
+  default:
+    z++;
+  }
+  return z + 92;
+}
+
+// The child of the switch statement is not neccessarily a compound statement,
+// do not crash in this unusual case.
+char no_real_body(int in, int &out) {
+  switch (in)
+  case 42:
+    return 'A';
+
+  if (in > 77)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: warning: repeated branch in conditional chain [bugprone-branch-clone]
+    out++;
+// CHECK-MESSAGES: :[[@LINE-1]]:10: note: end of the original
+  else if (in > 55)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: clone 1 starts here
+    out++;
+  else if (in > 34)
+// CHECK-MESSAGES: :[[@LINE+1]]:5: note: clone 2 starts here
+    out++;
+
+  return '|';
+}
+
+// Duff's device [https://en.wikipedia.org/wiki/Duff's_device]
+// The check does not try to distinguish branches in this sort of convoluted
+// code, but it should avoid crashing.
+void send(short *to, short *from, int count)
+{
+    int n = (count + 7) / 8;
+    switch (count % 8) {
+    case 0: do { *to = *from++;
+    case 7:      *to = *from++;
+    case 6:      *to = *from++;
+    case 5:      *to = *from++;
+    case 4:      *to = *from++;
+    case 3:      *to = *from++;
+    case 2:      *to = *from++;
+    case 1:      *to = *from++;
+            } while (--n > 0);
+    }
+}
+
+//=========--------------------==========//
+
+void ternary1(bool b, int &x) {
+// CHECK-MESSAGES: :[[@LINE+1]]:6: warning: conditional operator with identical true and false expressions [bugprone-branch-clone]
+  (b ? x : x) = 42;
+}
+
+int ternary2(bool b, int x) {
+// CHECK-MESSAGES: :[[@LINE+1]]:12: warning: conditional operator with identical true and false expressions [bugprone-branch-clone]
+  return b ? 42 : 42;
+}
+
+int ternary3(bool b, int x) {
+  return b ? 42 : 43;
+}
+
+int ternary4(bool b, int x) {
+  return b ? true ? 45 : 44 : false ? 45 : 44;
+}
+
+// We do not detect chains of conditional operators.
+int ternary5(bool b1, bool b2 int x) {
+  return b1 ? 42 : b2 ? 43 : 42;
+}