clang 19.0.0git
UndefinedAssignmentChecker.cpp
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1//===--- UndefinedAssignmentChecker.h ---------------------------*- C++ -*--==//
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// This defines UndefinedAssignmentChecker, a builtin check in ExprEngine that
10// checks for assigning undefined values.
11//
12//===----------------------------------------------------------------------===//
13
19
20using namespace clang;
21using namespace ento;
22
23namespace {
24class UndefinedAssignmentChecker
25 : public Checker<check::Bind> {
26 const BugType BT{this, "Assigned value is garbage or undefined"};
27
28public:
29 void checkBind(SVal location, SVal val, const Stmt *S,
30 CheckerContext &C) const;
31};
32}
33
34void UndefinedAssignmentChecker::checkBind(SVal location, SVal val,
35 const Stmt *StoreE,
36 CheckerContext &C) const {
37 if (!val.isUndef())
38 return;
39
40 // Do not report assignments of uninitialized values inside swap functions.
41 // This should allow to swap partially uninitialized structs
42 if (const FunctionDecl *EnclosingFunctionDecl =
43 dyn_cast<FunctionDecl>(C.getStackFrame()->getDecl()))
44 if (C.getCalleeName(EnclosingFunctionDecl) == "swap")
45 return;
46
47 ExplodedNode *N = C.generateErrorNode();
48
49 if (!N)
50 return;
51
52 // Generate a report for this bug.
54 llvm::raw_svector_ostream OS(Str);
55
56 const Expr *ex = nullptr;
57
58 while (StoreE) {
59 if (const UnaryOperator *U = dyn_cast<UnaryOperator>(StoreE)) {
60 OS << "The expression is an uninitialized value. "
61 "The computed value will also be garbage";
62
63 ex = U->getSubExpr();
64 break;
65 }
66
67 if (const BinaryOperator *B = dyn_cast<BinaryOperator>(StoreE)) {
68 if (B->isCompoundAssignmentOp()) {
69 if (C.getSVal(B->getLHS()).isUndef()) {
70 OS << "The left expression of the compound assignment is an "
71 "uninitialized value. The computed value will also be garbage";
72 ex = B->getLHS();
73 break;
74 }
75 }
76
77 ex = B->getRHS();
78 break;
79 }
80
81 if (const DeclStmt *DS = dyn_cast<DeclStmt>(StoreE)) {
82 const VarDecl *VD = cast<VarDecl>(DS->getSingleDecl());
83 ex = VD->getInit();
84 }
85
86 if (const auto *CD =
87 dyn_cast<CXXConstructorDecl>(C.getStackFrame()->getDecl())) {
88 if (CD->isImplicit()) {
89 for (auto *I : CD->inits()) {
90 if (I->getInit()->IgnoreImpCasts() == StoreE) {
91 OS << "Value assigned to field '" << I->getMember()->getName()
92 << "' in implicit constructor is garbage or undefined";
93 break;
94 }
95 }
96 }
97 }
98
99 break;
100 }
101
102 if (OS.str().empty())
103 OS << BT.getDescription();
104
105 auto R = std::make_unique<PathSensitiveBugReport>(BT, OS.str(), N);
106 if (ex) {
107 R->addRange(ex->getSourceRange());
109 }
110 C.emitReport(std::move(R));
111}
112
113void ento::registerUndefinedAssignmentChecker(CheckerManager &mgr) {
114 mgr.registerChecker<UndefinedAssignmentChecker>();
115}
116
117bool ento::shouldRegisterUndefinedAssignmentChecker(const CheckerManager &mgr) {
118 return true;
119}
A builtin binary operation expression such as "x + y" or "x <= y".
Definition: Expr.h:3847
DeclStmt - Adaptor class for mixing declarations with statements and expressions.
Definition: Stmt.h:1495
This represents one expression.
Definition: Expr.h:110
Represents a function declaration or definition.
Definition: Decl.h:1959
Stmt - This represents one statement.
Definition: Stmt.h:84
SourceRange getSourceRange() const LLVM_READONLY
SourceLocation tokens are not useful in isolation - they are low level value objects created/interpre...
Definition: Stmt.cpp:326
UnaryOperator - This represents the unary-expression's (except sizeof and alignof),...
Definition: Expr.h:2183
Represents a variable declaration or definition.
Definition: Decl.h:918
const Expr * getInit() const
Definition: Decl.h:1352
CHECKER * registerChecker(AT &&... Args)
Used to register checkers.
SVal - This represents a symbolic expression, which can be either an L-value or an R-value.
Definition: SVals.h:55
bool isUndef() const
Definition: SVals.h:104
bool trackExpressionValue(const ExplodedNode *N, const Expr *E, PathSensitiveBugReport &R, TrackingOptions Opts={})
Attempts to add visitors to track expression value back to its point of origin.
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