llvm-project/clang-tools-extra/clang-tidy/readability/UseNumericLimitsCheck.cpp

//===--- UseNumericLimitsCheck.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 "UseNumericLimitsCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Preprocessor.h"
#include <cmath>
#include <limits>

using namespace clang::ast_matchers;

namespace clang::tidy::readability {

UseNumericLimitsCheck::UseNumericLimitsCheck(StringRef Name,
                                             ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      SignedConstants{
          {std::numeric_limits<int8_t>::min(),
           "std::numeric_limits<int8_t>::min()"},
          {std::numeric_limits<int8_t>::max(),
           "std::numeric_limits<int8_t>::max()"},
          {std::numeric_limits<int16_t>::min(),
           "std::numeric_limits<int16_t>::min()"},
          {std::numeric_limits<int16_t>::max(),
           "std::numeric_limits<int16_t>::max()"},
          {std::numeric_limits<int32_t>::min(),
           "std::numeric_limits<int32_t>::min()"},
          {std::numeric_limits<int32_t>::max(),
           "std::numeric_limits<int32_t>::max()"},
          {std::numeric_limits<int64_t>::min(),
           "std::numeric_limits<int64_t>::min()"},
          {std::numeric_limits<int64_t>::max(),
           "std::numeric_limits<int64_t>::max()"},
      },
      UnsignedConstants{
          {std::numeric_limits<uint8_t>::max(),
           "std::numeric_limits<uint8_t>::max()"},
          {std::numeric_limits<uint16_t>::max(),
           "std::numeric_limits<uint16_t>::max()"},
          {std::numeric_limits<uint32_t>::max(),
           "std::numeric_limits<uint32_t>::max()"},
          {std::numeric_limits<uint64_t>::max(),
           "std::numeric_limits<uint64_t>::max()"},
      },
      Inserter(Options.getLocalOrGlobal("IncludeStyle",
                                        utils::IncludeSorter::IS_LLVM),
               areDiagsSelfContained()) {}

void UseNumericLimitsCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "IncludeStyle", Inserter.getStyle());
}

void UseNumericLimitsCheck::registerMatchers(MatchFinder *Finder) {
  auto PositiveIntegerMatcher = [](auto Value) {
    return unaryOperator(hasOperatorName("+"),
                         hasUnaryOperand(integerLiteral(equals(Value))
                                             .bind("positive-integer-literal")))
        .bind("unary-op");
  };

  auto NegativeIntegerMatcher = [](auto Value) {
    return unaryOperator(hasOperatorName("-"),
                         hasUnaryOperand(integerLiteral(equals(-Value))
                                             .bind("negative-integer-literal")))
        .bind("unary-op");
  };

  auto BareIntegerMatcher = [](auto Value) {
    return integerLiteral(allOf(unless(hasParent(unaryOperator(
                                    hasAnyOperatorName("-", "+")))),
                                equals(Value)))
        .bind("bare-integer-literal");
  };

  for (const auto &[Value, _] : SignedConstants) {
    if (Value < 0) {
      Finder->addMatcher(NegativeIntegerMatcher(Value), this);
    } else {
      Finder->addMatcher(
          expr(anyOf(PositiveIntegerMatcher(Value), BareIntegerMatcher(Value))),
          this);
    }
  }

  for (const auto &[Value, _] : UnsignedConstants) {
    Finder->addMatcher(
        expr(anyOf(PositiveIntegerMatcher(Value), BareIntegerMatcher(Value))),
        this);
  }
}

void UseNumericLimitsCheck::registerPPCallbacks(
    const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
  Inserter.registerPreprocessor(PP);
}

void UseNumericLimitsCheck::check(const MatchFinder::MatchResult &Result) {
  const IntegerLiteral *MatchedDecl = nullptr;

  const IntegerLiteral *NegativeMatchedDecl =
      Result.Nodes.getNodeAs<IntegerLiteral>("negative-integer-literal");
  const IntegerLiteral *PositiveMatchedDecl =
      Result.Nodes.getNodeAs<IntegerLiteral>("positive-integer-literal");
  const IntegerLiteral *BareMatchedDecl =
      Result.Nodes.getNodeAs<IntegerLiteral>("bare-integer-literal");

  if (NegativeMatchedDecl != nullptr)
    MatchedDecl = NegativeMatchedDecl;
  else if (PositiveMatchedDecl != nullptr)
    MatchedDecl = PositiveMatchedDecl;
  else if (BareMatchedDecl != nullptr)
    MatchedDecl = BareMatchedDecl;

  const llvm::APInt MatchedIntegerConstant = MatchedDecl->getValue();

  auto Fixer = [&](auto SourceValue, auto Value,
                   const std::string &Replacement) {
    static_assert(std::is_same_v<decltype(SourceValue), decltype(Value)>,
                  "The types of SourceValue and Value must match");

    SourceLocation Location = MatchedDecl->getExprLoc();
    SourceRange Range{MatchedDecl->getBeginLoc(), MatchedDecl->getEndLoc()};

    // Only valid if unary operator is present
    const UnaryOperator *UnaryOpExpr =
        Result.Nodes.getNodeAs<UnaryOperator>("unary-op");

    if (MatchedDecl == NegativeMatchedDecl && -SourceValue == Value) {
      Range = SourceRange(UnaryOpExpr->getBeginLoc(), UnaryOpExpr->getEndLoc());
      Location = UnaryOpExpr->getExprLoc();
      SourceValue = -SourceValue;
    } else if (MatchedDecl == PositiveMatchedDecl && SourceValue == Value) {
      Range = SourceRange(UnaryOpExpr->getBeginLoc(), UnaryOpExpr->getEndLoc());
      Location = UnaryOpExpr->getExprLoc();
    } else if (MatchedDecl != BareMatchedDecl || SourceValue != Value) {
      return;
    }

    diag(Location,
         "the constant '%0' is being utilized; consider using '%1' instead")
        << SourceValue << Replacement
        << FixItHint::CreateReplacement(Range, Replacement)
        << Inserter.createIncludeInsertion(
               Result.SourceManager->getFileID(Location), "<limits>");
  };

  for (const auto &[Value, Replacement] : SignedConstants)
    Fixer(MatchedIntegerConstant.getSExtValue(), Value, Replacement);

  for (const auto &[Value, Replacement] : UnsignedConstants)
    Fixer(MatchedIntegerConstant.getZExtValue(), Value, Replacement);
}

} // namespace clang::tidy::readability