PiotrZSL updated this revision to Diff 551758.
PiotrZSL added a comment.
Rebase + Ping
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D144429/new/
https://reviews.llvm.org/D144429
Files:
clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
clang-tools-extra/clang-tidy/bugprone/ChainedComparisonCheck.cpp
clang-tools-extra/clang-tidy/bugprone/ChainedComparisonCheck.h
clang-tools-extra/docs/ReleaseNotes.rst
clang-tools-extra/docs/clang-tidy/checks/bugprone/chained-comparison.rst
clang-tools-extra/docs/clang-tidy/checks/list.rst
clang-tools-extra/test/clang-tidy/checkers/bugprone/chained-comparison.cpp
Index: clang-tools-extra/test/clang-tidy/checkers/bugprone/chained-comparison.cpp
===================================================================
--- /dev/null
+++ clang-tools-extra/test/clang-tidy/checkers/bugprone/chained-comparison.cpp
@@ -0,0 +1,91 @@
+// RUN: %check_clang_tidy -std=c++98-or-later %s bugprone-chained-comparison %t
+
+void badly_chained_1(int x, int y, int z)
+{
+ bool result = x < y < z;
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:19: warning: chained comparison 'a < b < c' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+
+void badly_chained_2(int x, int y, int z)
+{
+ bool result = x <= y <= z;
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:19: warning: chained comparison 'a <= b <= c' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+
+void badly_chained_3(int x, int y, int z)
+{
+ bool result = x > y > z;
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:19: warning: chained comparison 'a > b > c' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+
+void badly_chained_4(int x, int y, int z)
+{
+ bool result = x >= y >= z;
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:19: warning: chained comparison 'a >= b >= c' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+
+void badly_chained_5(int x, int y, int z)
+{
+ bool result = x == y != z;
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:19: warning: chained comparison 'a == b != c' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+
+void badly_chained_6(bool x, bool y, bool z)
+{
+ bool result = x != y == z;
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:19: warning: chained comparison 'a != b == c' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+
+void badly_chained_multiple(bool a, bool b, bool c, bool d, bool e, bool f, bool g, bool h)
+{
+ bool result = a == b == c == d == e == f == g == h;
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:19: warning: chained comparison 'a == b == c == d == e == f == g == h' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+
+void badly_chained_limit(bool v[29])
+{
+// CHECK-MESSAGES: :[[@LINE+1]]:19: warning: chained comparison 'a == b == c == d == e == f == g == h == i == j == k == l == m == n == o == p == q == r == s == t == u == v == w == x == y == z ...' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+ bool result = v[0] == v[1] == v[2] == v[3] == v[4] == v[5] == v[6] == v[7] ==
+ v[8] == v[9] == v[10] == v[11] == v[12] == v[13] == v[14] ==
+ v[15] == v[16] == v[17] == v[18] == v[19] == v[20] == v[21] ==
+ v[22] == v[23] == v[24] == v[25] == v[26] == v[27] == v[28];
+
+}
+
+void badly_chained_parens2(int x, int y, int z, int t, int a, int b)
+{
+ bool result = (x < y) < (z && t) > (a == b);
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:19: warning: chained comparison 'a < b > c' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+
+void badly_chained_inner(int x, int y, int z, int t, int u)
+{
+ bool result = x && y < z < t && u;
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:24: warning: chained comparison 'a < b < c' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+
+void properly_chained_1(int x, int y, int z)
+{
+ bool result = x < y && y < z;
+}
+
+void properly_chained_2(int x, int y, bool z)
+{
+ bool result = (x < y) == z;
+}
+
+struct Value {
+ bool operator<(const Value&) const;
+};
+
+bool operator==(bool, const Value&);
+
+bool badWithCppOperator(Value a, Value b, Value c) {
+ return a < b == c;
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:12: warning: chained comparison 'a < b == c' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
+
+bool mixedBinaryAndCpp(Value a, Value b, bool c) {
+ return a < b == c;
+}
+// CHECK-MESSAGES: :[[@LINE-2]]:12: warning: chained comparison 'a < b == c' may generate unintended results, use parentheses to specify order of evaluation or a logical operator to separate comparison expressions [bugprone-chained-comparison]
Index: clang-tools-extra/docs/clang-tidy/checks/list.rst
===================================================================
--- clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ clang-tools-extra/docs/clang-tidy/checks/list.rst
@@ -82,6 +82,7 @@
`bugprone-bad-signal-to-kill-thread <bugprone/bad-signal-to-kill-thread.html>`_,
`bugprone-bool-pointer-implicit-conversion <bugprone/bool-pointer-implicit-conversion.html>`_, "Yes"
`bugprone-branch-clone <bugprone/branch-clone.html>`_,
+ `bugprone-chained-comparison <bugprone/chained-comparison.html>`_,
`bugprone-copy-constructor-init <bugprone/copy-constructor-init.html>`_, "Yes"
`bugprone-dangling-handle <bugprone/dangling-handle.html>`_,
`bugprone-dynamic-static-initializers <bugprone/dynamic-static-initializers.html>`_,
Index: clang-tools-extra/docs/clang-tidy/checks/bugprone/chained-comparison.rst
===================================================================
--- /dev/null
+++ clang-tools-extra/docs/clang-tidy/checks/bugprone/chained-comparison.rst
@@ -0,0 +1,73 @@
+.. title:: clang-tidy - bugprone-chained-comparison
+
+bugprone-chained-comparison
+===========================
+
+Check detects chained comparison operators that can lead to unintended
+behavior or logical errors in C++ code.
+
+Chained comparisons are expressions that use multiple comparison operators
+to compare three or more values. For example, the expression ``a < b < c``
+compares the values of ``a``, ``b``, and ``c``. However, this expression does
+not evaluate as ``(a < b) && (b < c)``, which is probably what the developer
+intended. Instead, it evaluates as ``(a < b) < c``, which may produce
+unintended results, especially when the types of ``a``, ``b``, and ``c`` are
+different.
+
+To avoid such errors, the check will issue a warning when a chained
+comparison operator is detected, suggesting to use parentheses to specify
+the order of evaluation or to use a logical operator to separate comparison
+expressions.
+
+Consider the following examples:
+
+.. code-block:: c++
+
+ int a = 2, b = 6, c = 4;
+ if (a < b < c) {
+ // This block will be executed
+ }
+
+
+In this example, the developer intended to check if ``a`` is less than ``b``
+and ``b`` is less than ``c``. However, the expression ``a < b < c`` is
+equivalent to ``(a < b) < c``. Since ``a < b`` is ``true``, the expression
+``(a < b) < c`` is evaluated as ``1 < c``, which is equivalent to ``true < c``
+and is invalid in this case as ``b < c`` is ``false``.
+
+Even that above issue could be detected as comparison of ``int`` to ``bool``,
+there is more dangerous example:
+
+.. code-block:: c++
+
+ bool a = false, b = false, c = true;
+ if (a == b == c) {
+ // This block will be executed
+ }
+
+In this example, the developer intended to check if ``a``, ``b``, and ``c`` are
+all equal. However, the expression ``a == b == c`` is evaluated as
+``(a == b) == c``. Since ``a == b`` is true, the expression ``(a == b) == c``
+is evaluated as ``true == c``, which is equivalent to ``true == true``.
+This comparison yields ``true``, even though ``a`` and ``b`` are ``false``, and
+are not equal to ``c``.
+
+To avoid this issue, the developer can use a logical operator to separate the
+comparison expressions, like this:
+
+.. code-block:: c++
+
+ if (a == b && b == c) {
+ // This block will not be executed
+ }
+
+
+Alternatively, use of parentheses in the comparison expressions can make the
+developer's intention more explicit and help avoid misunderstanding.
+
+.. code-block:: c++
+
+ if ((a == b) == c) {
+ // This block will be executed
+ }
+
Index: clang-tools-extra/docs/ReleaseNotes.rst
===================================================================
--- clang-tools-extra/docs/ReleaseNotes.rst
+++ clang-tools-extra/docs/ReleaseNotes.rst
@@ -116,6 +116,12 @@
New checks
^^^^^^^^^^
+- New :doc:`bugprone-chained-comparison
+ <clang-tidy/checks/bugprone/chained-comparison>` check.
+
+ Check detects chained comparison operators that can lead to unintended
+ behavior or logical errors in C++ code.
+
- New :doc:`bugprone-inc-dec-in-conditions
<clang-tidy/checks/bugprone/inc-dec-in-conditions>` check.
@@ -187,7 +193,7 @@
ignore delegate constructors.
- Improved :doc `cppcoreguidelines-pro-bounds-array-to-pointer-decay
- <clang-tidy/checks/cppcoreguidelines/pro-bounds-array-to-pointer-decay>` check
+ <clang-tidy/checks/cppcoreguidelines/pro-bounds-array-to-pointer-decay>` check
to ignore predefined expression (e.g., ``__func__``, ...).
- Improved :doc:`cppcoreguidelines-pro-type-member-init
Index: clang-tools-extra/clang-tidy/bugprone/ChainedComparisonCheck.h
===================================================================
--- /dev/null
+++ clang-tools-extra/clang-tidy/bugprone/ChainedComparisonCheck.h
@@ -0,0 +1,34 @@
+//===--- ChainedComparisonCheck.h - clang-tidy ------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_CHAINEDCOMPARISONCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_CHAINEDCOMPARISONCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::bugprone {
+
+/// Check detects chained comparison operators that can lead to unintended
+/// behavior or logical errors in C++ code.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/bugprone/chained-comparison.html
+class ChainedComparisonCheck : public ClangTidyCheck {
+public:
+ ChainedComparisonCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+ bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+ return LangOpts.CPlusPlus;
+ }
+};
+
+} // namespace clang::tidy::bugprone
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_CHAINEDCOMPARISONCHECK_H
Index: clang-tools-extra/clang-tidy/bugprone/ChainedComparisonCheck.cpp
===================================================================
--- /dev/null
+++ clang-tools-extra/clang-tidy/bugprone/ChainedComparisonCheck.cpp
@@ -0,0 +1,164 @@
+//===--- ChainedComparisonCheck.cpp - clang-tidy --------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "ChainedComparisonCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+#include <algorithm>
+#include <array>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+namespace {
+
+bool isExprAComparisonOperator(const Expr *E) {
+ if (const auto *Op = dyn_cast_or_null<BinaryOperator>(E->IgnoreImplicit()))
+ return Op->isComparisonOp();
+ if (const auto *Op =
+ dyn_cast_or_null<CXXOperatorCallExpr>(E->IgnoreImplicit()))
+ return Op->isComparisonOp();
+ return false;
+}
+
+AST_MATCHER(BinaryOperator,
+ hasBinaryOperatorAChildComparisonOperatorWithoutParen) {
+ return isExprAComparisonOperator(Node.getLHS()) ||
+ isExprAComparisonOperator(Node.getRHS());
+}
+
+AST_MATCHER(CXXOperatorCallExpr,
+ hasCppOperatorAChildComparisonOperatorWithoutParen) {
+ return std::any_of(Node.arg_begin(), Node.arg_end(),
+ isExprAComparisonOperator);
+}
+
+constexpr std::array<llvm::StringRef, 26U> Letters = {
+ "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m",
+ "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
+
+struct ChainedComparisonData {
+ llvm::SmallString<256U> Name;
+ llvm::SmallVector<const Expr *, 26U> Operands;
+ bool Full = false;
+
+ void Add(const Expr *Operand) {
+ if (Full)
+ return;
+ if (!Name.empty())
+ Name += ' ';
+ Name += Letters[Operands.size()];
+ Operands.push_back(Operand);
+
+ if (Operands.size() == Letters.size()) {
+ Name += " ...";
+ Full = true;
+ }
+ }
+
+ void Add(llvm::StringRef Opcode) {
+ if (Full)
+ return;
+
+ Name += ' ';
+ Name += Opcode.str();
+ }
+};
+
+} // namespace
+
+static void extractData(const Expr *Op, ChainedComparisonData &Output);
+
+inline bool extractData(const BinaryOperator *Op,
+ ChainedComparisonData &Output) {
+ if (!Op)
+ return false;
+
+ if (isExprAComparisonOperator(Op->getLHS()))
+ extractData(Op->getLHS()->IgnoreImplicit(), Output);
+ else
+ Output.Add(Op->getLHS()->IgnoreUnlessSpelledInSource());
+
+ Output.Add(Op->getOpcodeStr());
+
+ if (isExprAComparisonOperator(Op->getRHS()))
+ extractData(Op->getRHS()->IgnoreImplicit(), Output);
+ else
+ Output.Add(Op->getRHS()->IgnoreUnlessSpelledInSource());
+ return true;
+}
+
+inline bool extractData(const CXXOperatorCallExpr *Op,
+ ChainedComparisonData &Output) {
+ if (!Op || Op->getNumArgs() != 2U)
+ return false;
+
+ const Expr *FirstArg = Op->getArg(0U)->IgnoreImplicit();
+ if (isExprAComparisonOperator(FirstArg))
+ extractData(FirstArg, Output);
+ else
+ Output.Add(FirstArg->IgnoreUnlessSpelledInSource());
+
+ Output.Add(getOperatorSpelling(Op->getOperator()));
+
+ const Expr *SecondArg = Op->getArg(1U)->IgnoreImplicit();
+ if (isExprAComparisonOperator(SecondArg))
+ extractData(SecondArg, Output);
+ else
+ Output.Add(SecondArg->IgnoreUnlessSpelledInSource());
+ return true;
+}
+
+static void extractData(const Expr *OpExpr, ChainedComparisonData &Output) {
+ OpExpr->dump();
+ extractData(dyn_cast_or_null<BinaryOperator>(OpExpr), Output) ||
+ extractData(dyn_cast_or_null<CXXOperatorCallExpr>(OpExpr), Output);
+}
+
+void ChainedComparisonCheck::registerMatchers(MatchFinder *Finder) {
+ const auto OperatorMatcher = expr(anyOf(
+ binaryOperator(isComparisonOperator(),
+ hasBinaryOperatorAChildComparisonOperatorWithoutParen()),
+ cxxOperatorCallExpr(
+ isComparisonOperator(),
+ hasCppOperatorAChildComparisonOperatorWithoutParen())));
+
+ Finder->addMatcher(
+ traverse(TK_IgnoreUnlessSpelledInSource,
+ expr(unless(isExpansionInSystemHeader()), OperatorMatcher,
+ unless(hasParent(OperatorMatcher)))
+ .bind("op")),
+ this);
+}
+
+void ChainedComparisonCheck::check(const MatchFinder::MatchResult &Result) {
+ const auto *MatchedOperator = Result.Nodes.getNodeAs<Expr>("op");
+
+ ChainedComparisonData Data;
+ extractData(MatchedOperator, Data);
+
+ if (Data.Operands.empty())
+ return;
+
+ diag(MatchedOperator->getBeginLoc(),
+ "chained comparison '%0' may generate unintended results, use "
+ "parentheses to specify order of evaluation or a logical operator to "
+ "separate comparison expressions")
+ << llvm::StringRef(Data.Name).trim();
+
+ for (std::size_t Index = 0U; Index < Data.Operands.size(); ++Index) {
+ diag(Data.Operands[Index]->getBeginLoc(), "operand '%0' is here",
+ DiagnosticIDs::Note)
+ << Letters[Index];
+ }
+}
+
+} // namespace clang::tidy::bugprone
Index: clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
===================================================================
--- clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
+++ clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
@@ -11,6 +11,7 @@
BoolPointerImplicitConversionCheck.cpp
BranchCloneCheck.cpp
BugproneTidyModule.cpp
+ ChainedComparisonCheck.cpp
CopyConstructorInitCheck.cpp
DanglingHandleCheck.cpp
DynamicStaticInitializersCheck.cpp
Index: clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
===================================================================
--- clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
+++ clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
@@ -16,6 +16,7 @@
#include "BadSignalToKillThreadCheck.h"
#include "BoolPointerImplicitConversionCheck.h"
#include "BranchCloneCheck.h"
+#include "ChainedComparisonCheck.h"
#include "CopyConstructorInitCheck.h"
#include "DanglingHandleCheck.h"
#include "DynamicStaticInitializersCheck.h"
@@ -102,6 +103,8 @@
CheckFactories.registerCheck<BoolPointerImplicitConversionCheck>(
"bugprone-bool-pointer-implicit-conversion");
CheckFactories.registerCheck<BranchCloneCheck>("bugprone-branch-clone");
+ CheckFactories.registerCheck<ChainedComparisonCheck>(
+ "bugprone-chained-comparison");
CheckFactories.registerCheck<CopyConstructorInitCheck>(
"bugprone-copy-constructor-init");
CheckFactories.registerCheck<DanglingHandleCheck>(
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