[clang-tools-extra] [clang-tidy] Create a check for signed and unsigned integers comparison (PR #113144)

[Carlos Galvez via cfe-commits]

================
@@ -0,0 +1,173 @@
+//===--- UseIntegerSignComparisonCheck.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 "UseIntegerSignComparisonCheck.h"
+#include "clang/AST/Expr.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+using namespace clang::ast_matchers::internal;
+
+namespace clang::tidy::modernize {
+
+/// Find if the passed type is the actual "char" type,
+/// not applicable to explicit "signed char" or "unsigned char" types.
+static bool isActualCharType(const clang::QualType &Ty) {
+  using namespace clang;
+  const Type *DesugaredType = Ty->getUnqualifiedDesugaredType();
+  if (const auto *BT = llvm::dyn_cast<BuiltinType>(DesugaredType))
+    return (BT->getKind() == BuiltinType::Char_U ||
+            BT->getKind() == BuiltinType::Char_S);
+  return false;
+}
+
+namespace {
+AST_MATCHER(clang::QualType, isActualChar) {
+  return clang::tidy::modernize::isActualCharType(Node);
+}
+} // namespace
+
+static BindableMatcher<clang::Stmt>
+intCastExpression(bool IsSigned,
+                  const std::string &CastBindName = std::string()) {
+  // std::cmp_{} functions trigger a compile-time error if either LHS or RHS
+  // is a non-integer type, char, enum or bool
+  // (unsigned char/ signed char are Ok and can be used).
+  auto IntTypeExpr = expr(hasType(hasCanonicalType(qualType(
+      isInteger(), IsSigned ? isSignedInteger() : isUnsignedInteger(),
+      unless(isActualChar()), unless(booleanType()), unless(enumType())))));
+
+  const auto ImplicitCastExpr =
+      CastBindName.empty() ? implicitCastExpr(hasSourceExpression(IntTypeExpr))
+                           : implicitCastExpr(hasSourceExpression(IntTypeExpr))
+                                 .bind(CastBindName);
+
+  const auto CStyleCastExpr = cStyleCastExpr(has(ImplicitCastExpr));
+  const auto StaticCastExpr = cxxStaticCastExpr(has(ImplicitCastExpr));
+  const auto FunctionalCastExpr = cxxFunctionalCastExpr(has(ImplicitCastExpr));
+
+  return expr(anyOf(ImplicitCastExpr, CStyleCastExpr, StaticCastExpr,
+                    FunctionalCastExpr));
+}
+
+static StringRef parseOpCode(BinaryOperator::Opcode Code) {
+  switch (Code) {
+  case BO_LT:
+    return "cmp_less";
+  case BO_GT:
+    return "cmp_greater";
+  case BO_LE:
+    return "cmp_less_equal";
+  case BO_GE:
+    return "cmp_greater_equal";
+  case BO_EQ:
+    return "cmp_equal";
+  case BO_NE:
+    return "cmp_not_equal";
+  default:
+    return "";
+  }
+}
+
+UseIntegerSignComparisonCheck::UseIntegerSignComparisonCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      IncludeInserter(Options.getLocalOrGlobal("IncludeStyle",
+                                               utils::IncludeSorter::IS_LLVM),
+                      areDiagsSelfContained()) {}
+
+void UseIntegerSignComparisonCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IncludeStyle", IncludeInserter.getStyle());
+}
+
+void UseIntegerSignComparisonCheck::registerMatchers(MatchFinder *Finder) {
+  const auto SignedIntCastExpr = intCastExpression(true, "sIntCastExpression");
+  const auto UnSignedIntCastExpr = intCastExpression(false);
+
+  // Flag all operators "==", "<=", ">=", "<", ">", "!="
+  // that are used between signed/unsigned
+  const auto CompareOperator =
+      binaryOperator(hasAnyOperatorName("==", "<=", ">=", "<", ">", "!="),
+                     hasOperands(SignedIntCastExpr, UnSignedIntCastExpr),
+                     unless(isInTemplateInstantiation()))
+          .bind("intComparison");
+
+  Finder->addMatcher(CompareOperator, this);
+}
+
+void UseIntegerSignComparisonCheck::registerPPCallbacks(
+    const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
+  IncludeInserter.registerPreprocessor(PP);
+}
+
+void UseIntegerSignComparisonCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *SignedCastExpression =
+      Result.Nodes.getNodeAs<ImplicitCastExpr>("sIntCastExpression");
+  assert(SignedCastExpression);
+
+  // Ignore the match if we know that the signed int value is not negative.
+  Expr::EvalResult EVResult;
+  if (!SignedCastExpression->isValueDependent() &&
+      SignedCastExpression->getSubExpr()->EvaluateAsInt(EVResult,
+                                                        *Result.Context)) {
+    const llvm::APSInt SValue = EVResult.Val.getInt();
+    if (SValue.isNonNegative())
+      return;
+  }
+
+  const auto *BinaryOp =
+      Result.Nodes.getNodeAs<BinaryOperator>("intComparison");
+  if (BinaryOp == nullptr)
+    return;
+
+  const BinaryOperator::Opcode OpCode = BinaryOp->getOpcode();
+
+  const Expr *LHS = BinaryOp->getLHS()->IgnoreImpCasts();
+  const Expr *RHS = BinaryOp->getRHS()->IgnoreImpCasts();
+  if (LHS == nullptr || RHS == nullptr)
+    return;
+  const Expr *SubExprLHS = nullptr;
+  const Expr *SubExprRHS = nullptr;
+  SourceRange R1 = SourceRange(LHS->getBeginLoc());
+  SourceRange R2 = SourceRange(BinaryOp->getOperatorLoc());
+  SourceRange R3 = SourceRange(Lexer::getLocForEndOfToken(
+      RHS->getEndLoc(), 0, *Result.SourceManager, getLangOpts()));
+  if (const auto *LHSCast = llvm::dyn_cast<ExplicitCastExpr>(LHS)) {
+    SubExprLHS = LHSCast->getSubExpr();
+    R1 = SourceRange(LHS->getBeginLoc(),
+                     SubExprLHS->getBeginLoc().getLocWithOffset(-1));
+    R2.setBegin(Lexer::getLocForEndOfToken(
+        SubExprLHS->getEndLoc(), 0, *Result.SourceManager, getLangOpts()));
+  }
+  if (const auto *RHSCast = llvm::dyn_cast<ExplicitCastExpr>(RHS)) {
+    SubExprRHS = RHSCast->getSubExpr();
+    R2.setEnd(SubExprRHS->getBeginLoc().getLocWithOffset(-1));
+  }
+  DiagnosticBuilder Diag =
+      diag(BinaryOp->getBeginLoc(),
+           "comparison between 'signed' and 'unsigned' integers");
+  if (!getLangOpts().CPlusPlus20)
----------------
carlosgalvezp wrote:

Move this to IsLanguageVersionSupported

https://github.com/llvm/llvm-project/pull/113144