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
14#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
15#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
16#include "clang/StaticAnalyzer/Core/Checker.h"
17#include "clang/StaticAnalyzer/Core/CheckerManager.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19
20using namespace clang;
21using namespace ento;
22
23namespace {
24class UndefinedAssignmentChecker
25 : public Checker<check::Bind> {
26 const BugType BT{this, "Assigned value is uninitialized"};
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>(Val: C.getStackFrame()->getDecl()))
44 if (C.getCalleeName(FunDecl: EnclosingFunctionDecl) == "swap")
45 return;
46
47 ExplodedNode *N = C.generateErrorNode();
48
49 if (!N)
50 return;
51
52 // Generate a report for this bug.
53 llvm::SmallString<128> Str;
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>(Val: StoreE)) {
60 OS << "The expression uses uninitialized memory";
61
62 ex = U->getSubExpr();
63 break;
64 }
65
66 if (const BinaryOperator *B = dyn_cast<BinaryOperator>(Val: StoreE)) {
67 if (B->isCompoundAssignmentOp()) {
68 if (C.getSVal(S: B->getLHS()).isUndef()) {
69 OS << "The left expression of the compound assignment uses "
70 << "uninitialized memory";
71 ex = B->getLHS();
72 break;
73 }
74 }
75
76 ex = B->getRHS();
77 break;
78 }
79
80 if (const DeclStmt *DS = dyn_cast<DeclStmt>(Val: StoreE)) {
81 const VarDecl *VD = cast<VarDecl>(Val: DS->getSingleDecl());
82 ex = VD->getInit();
83 }
84
85 if (const auto *CD =
86 dyn_cast<CXXConstructorDecl>(Val: C.getStackFrame()->getDecl())) {
87 if (CD->isImplicit()) {
88 for (auto *I : CD->inits()) {
89 if (I->getInit()->IgnoreImpCasts() == StoreE) {
90 OS << "Value assigned to field '" << I->getMember()->getName()
91 << "' in implicit constructor is uninitialized";
92 break;
93 }
94 }
95 }
96 }
97
98 break;
99 }
100
101 if (OS.str().empty())
102 OS << BT.getDescription();
103
104 auto R = std::make_unique<PathSensitiveBugReport>(args: BT, args: OS.str(), args&: N);
105 if (ex) {
106 R->addRange(R: ex->getSourceRange());
107 bugreporter::trackExpressionValue(N, E: ex, R&: *R);
108 }
109 C.emitReport(R: std::move(R));
110}
111
112void ento::registerUndefinedAssignmentChecker(CheckerManager &mgr) {
113 mgr.registerChecker<UndefinedAssignmentChecker>();
114}
115
116bool ento::shouldRegisterUndefinedAssignmentChecker(const CheckerManager &mgr) {
117 return true;
118}
119