1 //===--- BoolPointerImplicitConversionCheck.cpp - clang-tidy --------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "BoolPointerImplicitConversionCheck.h"
10 
11 using namespace clang::ast_matchers;
12 
13 namespace clang {
14 namespace tidy {
15 namespace bugprone {
16 
17 void BoolPointerImplicitConversionCheck::registerMatchers(MatchFinder *Finder) {
18   // Look for ifs that have an implicit bool* to bool conversion in the
19   // condition. Filter negations.
20   Finder->addMatcher(
21       traverse(
22           ast_type_traits::TK_AsIs,
23           ifStmt(hasCondition(findAll(implicitCastExpr(
24                      unless(hasParent(unaryOperator(hasOperatorName("!")))),
25                      hasSourceExpression(expr(
26                          hasType(pointerType(pointee(booleanType()))),
27                          ignoringParenImpCasts(declRefExpr().bind("expr")))),
28                      hasCastKind(CK_PointerToBoolean)))),
29                  unless(isInTemplateInstantiation()))
30               .bind("if")),
31       this);
32 }
33 
34 void BoolPointerImplicitConversionCheck::check(
35     const MatchFinder::MatchResult &Result) {
36   auto *If = Result.Nodes.getNodeAs<IfStmt>("if");
37   auto *Var = Result.Nodes.getNodeAs<DeclRefExpr>("expr");
38 
39   // Ignore macros.
40   if (Var->getBeginLoc().isMacroID())
41     return;
42 
43   // Only allow variable accesses for now, no function calls or member exprs.
44   // Check that we don't dereference the variable anywhere within the if. This
45   // avoids false positives for checks of the pointer for nullptr before it is
46   // dereferenced. If there is a dereferencing operator on this variable don't
47   // emit a diagnostic. Also ignore array subscripts.
48   const Decl *D = Var->getDecl();
49   auto DeclRef = ignoringParenImpCasts(declRefExpr(to(equalsNode(D))));
50   if (!match(findAll(
51                  unaryOperator(hasOperatorName("*"), hasUnaryOperand(DeclRef))),
52              *If, *Result.Context)
53            .empty() ||
54       !match(findAll(arraySubscriptExpr(hasBase(DeclRef))), *If,
55              *Result.Context)
56            .empty() ||
57       // FIXME: We should still warn if the paremater is implicitly converted to
58       // bool.
59       !match(findAll(callExpr(hasAnyArgument(ignoringParenImpCasts(DeclRef)))),
60              *If, *Result.Context)
61            .empty() ||
62       !match(findAll(cxxDeleteExpr(has(ignoringParenImpCasts(expr(DeclRef))))),
63              *If, *Result.Context)
64            .empty())
65     return;
66 
67   diag(Var->getBeginLoc(), "dubious check of 'bool *' against 'nullptr', did "
68                            "you mean to dereference it?")
69       << FixItHint::CreateInsertion(Var->getBeginLoc(), "*");
70 }
71 
72 } // namespace bugprone
73 } // namespace tidy
74 } // namespace clang
75