clang-tidy/misc/BoolPointerImplicitConversion.cpp

//===--- BoolPointerImplicitConversion.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 "BoolPointerImplicitConversion.h"

using namespace clang::ast_matchers;

namespace clang {
namespace ast_matchers {

AST_MATCHER(CastExpr, isPointerToBoolean) {
  return Node.getCastKind() == CK_PointerToBoolean;
}
AST_MATCHER(QualType, isBoolean) { return Node->isBooleanType(); }

} // namespace ast_matchers

namespace tidy {

void BoolPointerImplicitConversion::registerMatchers(MatchFinder *Finder) {
  // Look for ifs that have an implicit bool* to bool conversion in the
  // condition. Filter negations.
  Finder->addMatcher(
      ifStmt(hasCondition(findAll(implicitCastExpr(
                 allOf(unless(hasParent(unaryOperator(hasOperatorName("!")))),
                       hasSourceExpression(expr(
                           hasType(pointerType(pointee(isBoolean()))),
                           ignoringParenImpCasts(declRefExpr().bind("expr")))),
                       isPointerToBoolean()))))).bind("if"),
      this);
}

void
BoolPointerImplicitConversion::check(const MatchFinder::MatchResult &Result) {
  auto *If = Result.Nodes.getStmtAs<IfStmt>("if");
  auto *Var = Result.Nodes.getStmtAs<DeclRefExpr>("expr");

  // Only allow variable accesses for now, no function calls or member exprs.
  // Check that we don't dereference the variable anywhere within the if. This
  // avoids false positives for checks of the pointer for nullptr before it is
  // dereferenced. If there is a dereferencing operator on this variable don't
  // emit a diagnostic. Also ignore array subscripts.
  const Decl *D = Var->getDecl();
  auto DeclRef = ignoringParenImpCasts(declRefExpr(to(equalsNode(D))));
  if (!match(findAll(
                 unaryOperator(hasOperatorName("*"), hasUnaryOperand(DeclRef))),
             *If, *Result.Context).empty() ||
      !match(findAll(arraySubscriptExpr(hasBase(DeclRef))), *If,
             *Result.Context).empty() ||
      // FIXME: We should still warn if the paremater is implicitly converted to
      // bool.
      !match(findAll(callExpr(hasAnyArgument(DeclRef))), *If, *Result.Context)
           .empty() ||
      !match(findAll(deleteExpr(has(expr(DeclRef)))), *If, *Result.Context)
           .empty())
    return;

  diag(Var->getLocStart(), "dubious check of 'bool *' against 'nullptr', did "
                           "you mean to dereference it?")
      << FixItHint::CreateInsertion(Var->getLocStart(), "*");
}

} // namespace tidy
} // namespace clang