madsravn updated this revision to Diff 82513.
madsravn added a comment.
Updated according to comments.
I have decided to keep the fixit for match1 a FIXME.
https://reviews.llvm.org/D27210
Files:
clang-tidy/misc/CMakeLists.txt
clang-tidy/misc/MiscTidyModule.cpp
clang-tidy/misc/StringCompareCheck.cpp
clang-tidy/misc/StringCompareCheck.h
docs/ReleaseNotes.rst
docs/clang-tidy/checks/list.rst
docs/clang-tidy/checks/misc-string-compare.rst
test/clang-tidy/misc-string-compare.cpp
Index: test/clang-tidy/misc-string-compare.cpp
===================================================================
--- test/clang-tidy/misc-string-compare.cpp
+++ test/clang-tidy/misc-string-compare.cpp
@@ -0,0 +1,121 @@
+// RUN: %check_clang_tidy %s misc-string-compare %t -- -- -std=c++11
+
+namespace std {
+template <typename T>
+class allocator {};
+template <typename T>
+class char_traits {};
+template <typename C, typename T = std::char_traits<C>, typename A = std::allocator<C>>
+class basic_string {
+public:
+ basic_string();
+ basic_string(const C *, unsigned int size);
+ int compare(const basic_string<char> &str) const;
+ int compare(const C *) const;
+ int compare(int, int, const basic_string<char> &str) const;
+ bool empty();
+};
+bool operator==(const basic_string<char> &lhs, const basic_string<char> &rhs);
+bool operator!=(const basic_string<char> &lhs, const basic_string<char> &rhs);
+bool operator==(const basic_string<char> &lhs, const char *&rhs);
+typedef basic_string<char> string;
+}
+
+void func(bool b);
+
+std::string comp() {
+ std::string str("a", 1);
+ return str;
+}
+
+void Test() {
+ std::string str1("a", 1);
+ std::string str2("b", 1);
+
+ if (str1.compare(str2)) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings; use the string equality operator instead [misc-string-compare]
+ if (!str1.compare(str2)) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:8: warning: do not use 'compare' to test equality of strings; use the string equality operator instead [misc-string-compare]
+ if (str1.compare(str2) == 0) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ // CHECK-FIXES: if (str1 == str2) {
+ if (str1.compare(str2) != 0) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ // CHECK-FIXES: if (str1 != str2) {
+ if (str1.compare("foo") == 0) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ // CHECK-FIXES: if (str1 == "foo") {
+ if (0 == str1.compare(str2)) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ // CHECK-FIXES: if (str2 == str1) {
+ if (0 != str1.compare(str2)) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ // CHECK-FIXES: if (str2 != str1) {
+ func(str1.compare(str2));
+ // CHECK-MESSAGES: [[@LINE-1]]:8: warning: do not use 'compare' to test equality of strings;
+ if (str2.empty() || str1.compare(str2) != 0) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:23: warning: do not use 'compare' to test equality of strings;
+ // CHECK-FIXES: if (str2.empty() || str1 != str2) {
+ std::string *str3 = &str1;
+ if (str3->compare(str2)) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ if (str3->compare(str2) == 0) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ // CHECK-FIXES: if (*str3 == str2) {
+ if (str2.compare(*str3) == 0) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ // CHECK-FIXES: if (str2 == *str3) {
+ if (comp().compare(str1) == 0) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ // CHECK-FIXES: if (comp() == str1) {
+ if (str1.compare(comp()) == 0) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ // CHECK-FIXES: if (str1 == comp()) {
+ if (str1.compare(comp())) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: do not use 'compare' to test equality of strings;
+ if (str1.compare(str2) == 1) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: 'compare' is not guaranteed to return -1 or 1; check for bigger or smaller than 0 instead
+ if (str1.compare(str2) == -1) {
+ }
+ // CHECK-MESSAGES: [[@LINE-2]]:7: warning: 'compare' is not guaranteed to return -1 or 1;
+}
+
+void Valid() {
+ std::string str1("a", 1);
+ std::string str2("b", 1);
+ if (str1 == str2) {
+ }
+ if (str1 != str2) {
+ }
+ if (str1.compare(str2) == str1.compare(str2)) {
+ }
+ if (0 == 0) {
+ }
+ if (str1.compare(str2) > 0) {
+ }
+ if (str1.compare(1, 3, str2)) {
+ }
+ if (str1.compare(str2) > 0) {
+ }
+ if (str1.compare(str2) < 0) {
+ }
+ if (str1.compare(str2) == 2) {
+ }
+ if (str1.compare(str2) == -3) {
+ }
+}
Index: docs/clang-tidy/checks/misc-string-compare.rst
===================================================================
--- docs/clang-tidy/checks/misc-string-compare.rst
+++ docs/clang-tidy/checks/misc-string-compare.rst
@@ -0,0 +1,54 @@
+.. title:: clang-tidy - misc-string-compare
+
+misc-string-compare
+===================
+
+Finds string comparisons using the compare method.
+
+A common mistake is to use the string's ``compare`` method instead of using the
+equality or inequality operators. The compare method is intended for sorting
+functions and thus returns a negative number, a positive number or
+zero depending on the lexicographical relationship between the strings compared.
+If an equality or inequality check can suffice, that is recommended. This is
+recommended to avoid the risk of incorrect interpretation of the return value
+and to simplify the code. The string equality and inequality operators can
+also be faster than the ``compare`` method due to early termination.
+
+Examples:
+
+.. code-block:: c++
+
+ std::string str1{"a"};
+ std::string str2{"b"};
+
+ // use str1 != str2 instead.
+ if (str1.compare(str2)) {
+ }
+
+ // use str1 == str2 instead.
+ if (!str1.compare(str2)) {
+ }
+
+ // use str1 == str2 instead.
+ if (str1.compare(str2) == 0) {
+ }
+
+ // use str1 != str2 instead.
+ if (str1.compare(str2) != 0) {
+ }
+
+ // use str1 == str2 instead.
+ if (0 == str1.compare(str2)) {
+ }
+
+ // use str1 != str2 instead.
+ if (0 != str1.compare(str2)) {
+ }
+
+ // Use str1 == "foo" instead.
+ if (str1.compare("foo") == 0) {
+ }
+
+The above code examples shows the list of if-statements that this check will
+give a warning for. All of them uses ``compare`` to check if equality or
+inequality of two strings instead of using the correct operators.
Index: docs/clang-tidy/checks/list.rst
===================================================================
--- docs/clang-tidy/checks/list.rst
+++ docs/clang-tidy/checks/list.rst
@@ -80,6 +80,7 @@
misc-sizeof-container
misc-sizeof-expression
misc-static-assert
+ misc-string-compare
misc-string-constructor
misc-string-integer-assignment
misc-string-literal-with-embedded-nul
Index: docs/ReleaseNotes.rst
===================================================================
--- docs/ReleaseNotes.rst
+++ docs/ReleaseNotes.rst
@@ -75,6 +75,11 @@
- `misc-pointer-and-integral-operation` check was removed.
+- New `misc-string-compare
+ <http://clang.llvm.org/extra/clang-tidy/checks/misc-string-compare.html>`_ check
+
+ Warns about using ``compare`` to test for string equality or ineqaulity.
+
- New `misc-use-after-move
<http://clang.llvm.org/extra/clang-tidy/checks/misc-use-after-move.html>`_ check
Index: clang-tidy/misc/StringCompareCheck.h
===================================================================
--- clang-tidy/misc/StringCompareCheck.h
+++ clang-tidy/misc/StringCompareCheck.h
@@ -0,0 +1,36 @@
+//===--- StringCompareCheck.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_MISC_STRING_COMPARE_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_STRING_COMPARE_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+/// This check flags all calls compare when used to check for string
+/// equality or inequality.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/misc-string-compare-check.html
+class StringCompareCheck : public ClangTidyCheck {
+public:
+ StringCompareCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_STRING_COMPARE_H
Index: clang-tidy/misc/StringCompareCheck.cpp
===================================================================
--- clang-tidy/misc/StringCompareCheck.cpp
+++ clang-tidy/misc/StringCompareCheck.cpp
@@ -0,0 +1,95 @@
+//===--- MiscStringCompare.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 "StringCompareCheck.h"
+#include "../utils/FixItHintUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Tooling/FixIt.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+static const StringRef CompareMessage = "do not use 'compare' to test equality "
+ "of strings; use the string equality "
+ "operator instead";
+static const StringRef GuaranteeMessage = "'compare' is not guaranteed to "
+ "return -1 or 1; check for bigger or "
+ "smaller than 0 instead";
+
+void StringCompareCheck::registerMatchers(MatchFinder *Finder) {
+ if (!getLangOpts().CPlusPlus)
+ return;
+ const auto StrCompare = cxxMemberCallExpr(
+ callee(cxxMethodDecl(hasName("compare"),
+ ofClass(classTemplateSpecializationDecl(
+ hasName("::std::basic_string"))))),
+ hasArgument(0, expr().bind("str2")), argumentCountIs(1),
+ callee(memberExpr(has(implicitCastExpr(anyOf(
+ has(callExpr(has(implicitCastExpr(has(declRefExpr())))).bind("str1")),
+ has(declRefExpr().bind("str1")),
+ has(implicitCastExpr(has(declRefExpr().bind("str1")))
+ .bind("str1pointer"))))))));
+
+ // First and second case: cast str.compare(str) to boolean.
+ Finder->addMatcher(implicitCastExpr(hasImplicitDestinationType(booleanType()),
+ has(StrCompare))
+ .bind("match1"),
+ this);
+
+ // Third and fourth case: str.compare(str) == 0 and str.compare(str) != 0.
+ Finder->addMatcher(
+ binaryOperator(
+ anyOf(hasOperatorName("=="), hasOperatorName("!=")),
+ hasEitherOperand(StrCompare.bind("compare")),
+ hasEitherOperand(anyOf(
+ integerLiteral(equals(0)).bind("zero"),
+ integerLiteral(equals(1)).bind("notzero"),
+ unaryOperator(
+ hasOperatorName("-"),
+ hasUnaryOperand(integerLiteral(equals(1)).bind("notzero"))))))
+ .bind("match2"),
+ this);
+}
+
+void StringCompareCheck::check(const MatchFinder::MatchResult &Result) {
+ if (const auto *Matched = Result.Nodes.getNodeAs<Stmt>("match1")) {
+ diag(Matched->getLocStart(), CompareMessage);
+ return;
+ }
+
+ if (const auto *Matched = Result.Nodes.getNodeAs<Stmt>("match2")) {
+ const ASTContext &Ctx = *Result.Context;
+
+ if (const auto *zero = Result.Nodes.getNodeAs<Stmt>("zero")) {
+ const auto *str1 = Result.Nodes.getNodeAs<Stmt>("str1");
+ const auto *str2 = Result.Nodes.getNodeAs<Stmt>("str2");
+ const auto *compare = Result.Nodes.getNodeAs<Stmt>("compare");
+
+ auto Diag = diag(Matched->getLocStart(), CompareMessage);
+
+ if (const auto *str1pointer = Result.Nodes.getNodeAs<Stmt>("str1pointer"))
+ Diag << FixItHint::CreateInsertion(str1pointer->getLocStart(), "*");
+
+ Diag << tooling::fixit::createReplacement(*zero, *str2, Ctx)
+ << tooling::fixit::createReplacement(*compare, *str1, Ctx);
+ } else if (Result.Nodes.getNodeAs<Stmt>("notzero")) {
+ diag(Matched->getLocStart(), GuaranteeMessage);
+ }
+ }
+
+ // FIXME: Add fixit to fix the code for case one and two (match1).
+}
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang
Index: clang-tidy/misc/MiscTidyModule.cpp
===================================================================
--- clang-tidy/misc/MiscTidyModule.cpp
+++ clang-tidy/misc/MiscTidyModule.cpp
@@ -35,6 +35,7 @@
#include "SizeofContainerCheck.h"
#include "SizeofExpressionCheck.h"
#include "StaticAssertCheck.h"
+#include "StringCompareCheck.h"
#include "StringConstructorCheck.h"
#include "StringIntegerAssignmentCheck.h"
#include "StringLiteralWithEmbeddedNulCheck.h"
@@ -105,6 +106,7 @@
CheckFactories.registerCheck<SizeofExpressionCheck>(
"misc-sizeof-expression");
CheckFactories.registerCheck<StaticAssertCheck>("misc-static-assert");
+ CheckFactories.registerCheck<StringCompareCheck>("misc-string-compare");
CheckFactories.registerCheck<StringConstructorCheck>(
"misc-string-constructor");
CheckFactories.registerCheck<StringIntegerAssignmentCheck>(
Index: clang-tidy/misc/CMakeLists.txt
===================================================================
--- clang-tidy/misc/CMakeLists.txt
+++ clang-tidy/misc/CMakeLists.txt
@@ -28,6 +28,7 @@
SizeofContainerCheck.cpp
SizeofExpressionCheck.cpp
StaticAssertCheck.cpp
+ StringCompareCheck.cpp
StringConstructorCheck.cpp
StringIntegerAssignmentCheck.cpp
StringLiteralWithEmbeddedNulCheck.cpp
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