DeleteNullPointerCheck.cpp

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//===----------------------------------------------------------------------===//
//
// 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 "DeleteNullPointerCheck.h"
#include "../utils/LexerUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Lexer.h"
 
using namespace clang::ast_matchers;
 
namespace clang::tidy::readability {
 
void DeleteNullPointerCheck::registerMatchers(MatchFinder *Finder) {
  const auto DeleteExpr =
      cxxDeleteExpr(
          has(declRefExpr(to(decl(equalsBoundNode("deletedPointer"))))))
          .bind("deleteExpr");
 
  const auto DeleteMemberExpr =
      cxxDeleteExpr(has(memberExpr(hasDeclaration(
                        fieldDecl(equalsBoundNode("deletedMemberPointer"))))))
          .bind("deleteMemberExpr");
 
  const auto PointerExpr = anyOf(
      declRefExpr(to(decl().bind("deletedPointer"))),
      memberExpr(hasDeclaration(fieldDecl().bind("deletedMemberPointer"))));
 
  const auto BinaryPointerCheckCondition = binaryOperator(hasOperands(
      anyOf(cxxNullPtrLiteralExpr(), integerLiteral(equals(0))), PointerExpr));
 
  Finder->addMatcher(
      ifStmt(hasCondition(anyOf(PointerExpr, BinaryPointerCheckCondition)),
             hasThen(anyOf(
                 DeleteExpr, DeleteMemberExpr,
                 compoundStmt(anyOf(has(DeleteExpr), has(DeleteMemberExpr)),
                              statementCountIs(1))
                     .bind("compound"))))
          .bind("ifWithDelete"),
      this);
}
 
void DeleteNullPointerCheck::check(const MatchFinder::MatchResult &Result) {
  const auto *IfWithDelete = Result.Nodes.getNodeAs<IfStmt>("ifWithDelete");
  const auto *Compound = Result.Nodes.getNodeAs<CompoundStmt>("compound");
 
  auto Diag = diag(
      IfWithDelete->getBeginLoc(),
      "'if' statement is unnecessary; deleting null pointer has no effect");
  if (IfWithDelete->hasElseStorage())
    return;
  // FIXME: generate fixit for this case.
 
  const std::optional<Token> PrevTok = utils::lexer::getPreviousToken(
      IfWithDelete->getThen()->getBeginLoc(), *Result.SourceManager,
      Result.Context->getLangOpts());
  if (!PrevTok)
    return;
 
  Diag << FixItHint::CreateRemoval(CharSourceRange::getTokenRange(
      IfWithDelete->getBeginLoc(), PrevTok->getLocation()));
 
  if (Compound) {
    Diag << FixItHint::CreateRemoval(
        CharSourceRange::getTokenRange(Compound->getLBracLoc()));
    Diag << FixItHint::CreateRemoval(
        CharSourceRange::getTokenRange(Compound->getRBracLoc()));
  }
}
 
} // namespace clang::tidy::readability