1 //===--- SignedBitwiseCheck.cpp - clang-tidy-------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "SignedBitwiseCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 
14 using namespace clang::ast_matchers;
15 using namespace clang::ast_matchers::internal;
16 
17 namespace clang {
18 namespace tidy {
19 namespace hicpp {
20 
21 void SignedBitwiseCheck::registerMatchers(MatchFinder *Finder) {
22   const auto SignedIntegerOperand =
23       expr(ignoringImpCasts(hasType(isSignedInteger()))).bind("signed-operand");
24 
25   // The standard [bitmask.types] allows some integral types to be implemented
26   // as signed types. Exclude these types from diagnosing for bitwise or(|) and
27   // bitwise and(&). Shifting and complementing such values is still not
28   // allowed.
29   const auto BitmaskType = namedDecl(anyOf(
30       hasName("::std::locale::category"), hasName("::std::ctype_base::mask"),
31       hasName("::std::ios_base::fmtflags"), hasName("::std::ios_base::iostate"),
32       hasName("::std::ios_base::openmode")));
33   const auto IsStdBitmask = ignoringImpCasts(declRefExpr(hasType(BitmaskType)));
34 
35   // Match binary bitwise operations on signed integer arguments.
36   Finder->addMatcher(
37       binaryOperator(
38           allOf(anyOf(hasOperatorName("^"), hasOperatorName("|"),
39                       hasOperatorName("&")),
40 
41                 unless(allOf(hasLHS(IsStdBitmask), hasRHS(IsStdBitmask))),
42 
43                 hasEitherOperand(SignedIntegerOperand),
44                 hasLHS(hasType(isInteger())), hasRHS(hasType(isInteger()))))
45           .bind("binary-no-sign-interference"),
46       this);
47 
48   // Shifting and complement is not allowed for any signed integer type because
49   // the sign bit may corrupt the result.
50   Finder->addMatcher(
51       binaryOperator(allOf(anyOf(hasOperatorName("<<"), hasOperatorName(">>")),
52                            hasEitherOperand(SignedIntegerOperand),
53                            hasLHS(hasType(isInteger())),
54                            hasRHS(hasType(isInteger()))))
55           .bind("binary-sign-interference"),
56       this);
57 
58   // Match unary operations on signed integer types.
59   Finder->addMatcher(unaryOperator(allOf(hasOperatorName("~"),
60                                          hasUnaryOperand(SignedIntegerOperand)))
61                          .bind("unary-signed"),
62                      this);
63 }
64 
65 void SignedBitwiseCheck::check(const MatchFinder::MatchResult &Result) {
66   const ast_matchers::BoundNodes &N = Result.Nodes;
67   const auto *SignedOperand = N.getNodeAs<Expr>("signed-operand");
68   assert(SignedOperand &&
69          "No signed operand found in problematic bitwise operations");
70 
71   bool IsUnary = false;
72   SourceLocation Location;
73 
74   if (const auto *UnaryOp = N.getNodeAs<UnaryOperator>("unary-signed")) {
75     IsUnary = true;
76     Location = UnaryOp->getLocStart();
77   } else {
78     if (const auto *BinaryOp =
79             N.getNodeAs<BinaryOperator>("binary-no-sign-interference"))
80       Location = BinaryOp->getLocStart();
81     else if (const auto *BinaryOp =
82                  N.getNodeAs<BinaryOperator>("binary-sign-interference"))
83       Location = BinaryOp->getLocStart();
84     else
85       llvm_unreachable("unexpected matcher result");
86   }
87 
88   diag(Location,
89        "use of a signed integer operand with a %select{binary|unary}0 bitwise "
90        "operator")
91       << IsUnary << SignedOperand->getSourceRange();
92 }
93 
94 } // namespace hicpp
95 } // namespace tidy
96 } // namespace clang
97