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       ifStmt(hasCondition(findAll(implicitCastExpr(
22                  unless(hasParent(unaryOperator(hasOperatorName("!")))),
23                  hasSourceExpression(
24                      expr(hasType(pointerType(pointee(booleanType()))),
25                           ignoringParenImpCasts(declRefExpr().bind("expr")))),
26                  hasCastKind(CK_PointerToBoolean)))),
27              unless(isInTemplateInstantiation()))
28           .bind("if"),
29       this);
30 }
31 
32 void BoolPointerImplicitConversionCheck::check(
33     const MatchFinder::MatchResult &Result) {
34   auto *If = Result.Nodes.getNodeAs<IfStmt>("if");
35   auto *Var = Result.Nodes.getNodeAs<DeclRefExpr>("expr");
36 
37   // Ignore macros.
38   if (Var->getBeginLoc().isMacroID())
39     return;
40 
41   // Only allow variable accesses for now, no function calls or member exprs.
42   // Check that we don't dereference the variable anywhere within the if. This
43   // avoids false positives for checks of the pointer for nullptr before it is
44   // dereferenced. If there is a dereferencing operator on this variable don't
45   // emit a diagnostic. Also ignore array subscripts.
46   const Decl *D = Var->getDecl();
47   auto DeclRef = ignoringParenImpCasts(declRefExpr(to(equalsNode(D))));
48   if (!match(findAll(
49                  unaryOperator(hasOperatorName("*"), hasUnaryOperand(DeclRef))),
50              *If, *Result.Context)
51            .empty() ||
52       !match(findAll(arraySubscriptExpr(hasBase(DeclRef))), *If,
53              *Result.Context)
54            .empty() ||
55       // FIXME: We should still warn if the paremater is implicitly converted to
56       // bool.
57       !match(findAll(callExpr(hasAnyArgument(ignoringParenImpCasts(DeclRef)))),
58              *If, *Result.Context)
59            .empty() ||
60       !match(findAll(cxxDeleteExpr(has(ignoringParenImpCasts(expr(DeclRef))))),
61              *If, *Result.Context)
62            .empty())
63     return;
64 
65   diag(Var->getBeginLoc(), "dubious check of 'bool *' against 'nullptr', did "
66                            "you mean to dereference it?")
67       << FixItHint::CreateInsertion(Var->getBeginLoc(), "*");
68 }
69 
70 } // namespace bugprone
71 } // namespace tidy
72 } // namespace clang
73