clang 10.0.0git

UndefBranchChecker.cpp
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1 //=== UndefBranchChecker.cpp -----------------------------------*- 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 file defines UndefBranchChecker, which checks for undefined branch
10 // condition.
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 #include <utility>
20
21 using namespace clang;
22 using namespace ento;
23
24 namespace {
25
26 class UndefBranchChecker : public Checker<check::BranchCondition> {
27 mutable std::unique_ptr<BuiltinBug> BT;
28
29 struct FindUndefExpr {
30 ProgramStateRef St;
31 const LocationContext *LCtx;
32
33 FindUndefExpr(ProgramStateRef S, const LocationContext *L)
34 : St(std::move(S)), LCtx(L) {}
35
36 const Expr *FindExpr(const Expr *Ex) {
37 if (!MatchesCriteria(Ex))
38 return nullptr;
39
40 for (const Stmt *SubStmt : Ex->children())
41 if (const Expr *ExI = dyn_cast_or_null<Expr>(SubStmt))
42 if (const Expr *E2 = FindExpr(ExI))
43 return E2;
44
45 return Ex;
46 }
47
48 bool MatchesCriteria(const Expr *Ex) {
49 return St->getSVal(Ex, LCtx).isUndef();
50 }
51 };
52
53 public:
54 void checkBranchCondition(const Stmt *Condition, CheckerContext &Ctx) const;
55 };
56
57 }
58
59 void UndefBranchChecker::checkBranchCondition(const Stmt *Condition,
60 CheckerContext &Ctx) const {
61 SVal X = Ctx.getSVal(Condition);
62 if (X.isUndef()) {
63 // Generate a sink node, which implicitly marks both outgoing branches as
64 // infeasible.
65 ExplodedNode *N = Ctx.generateErrorNode();
66 if (N) {
67 if (!BT)
68 BT.reset(new BuiltinBug(
69 this, "Branch condition evaluates to a garbage value"));
70
71 // What's going on here: we want to highlight the subexpression of the
72 // condition that is the most likely source of the "uninitialized
73 // branch condition." We do a recursive walk of the condition's
74 // subexpressions and roughly look for the most nested subexpression
75 // that binds to Undefined. We then highlight that expression's range.
76
77 // Get the predecessor node and check if is a PostStmt with the Stmt
78 // being the terminator condition. We want to inspect the state
79 // of that node instead because it will contain main information about
80 // the subexpressions.
81
82 // Note: any predecessor will do. They should have identical state,
83 // since all the BlockEdge did was act as an error sink since the value
84 // had to already be undefined.
85 assert (!N->pred_empty());
86 const Expr *Ex = cast<Expr>(Condition);
87 ExplodedNode *PrevN = *N->pred_begin();
88 ProgramPoint P = PrevN->getLocation();
89 ProgramStateRef St = N->getState();
90
91 if (Optional<PostStmt> PS = P.getAs<PostStmt>())
92 if (PS->getStmt() == Ex)
93 St = PrevN->getState();
94
95 FindUndefExpr FindIt(St, Ctx.getLocationContext());
96 Ex = FindIt.FindExpr(Ex);
97
98 // Emit the bug report.
99 auto R = std::make_unique<PathSensitiveBugReport>(
100 *BT, BT->getDescription(), N);
101 bugreporter::trackExpressionValue(N, Ex, *R);
102 R->addRange(Ex->getSourceRange());
103
104 Ctx.emitReport(std::move(R));
105 }
106 }
107 }
108
109 void ento::registerUndefBranchChecker(CheckerManager &mgr) {
110 mgr.registerChecker<UndefBranchChecker>();
111 }
112
113 bool ento::shouldRegisterUndefBranchChecker(const LangOptions &LO) {
114 return true;
115 }
ento
clang::Stmt
Stmt - This represents one statement.
Definition: Stmt.h:66
clang::ento::ProgramStateRef
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
Definition: ProgramState_Fwd.h:37
P
StringRef P
Definition: ASTMatchersInternal.cpp:485
clang::LocationContext
Definition: AnalysisDeclContext.h:216
BugType.h
llvm::Optional
Definition: LLVM.h:37
std
Definition: Format.h:2445
Checker.h
CheckerManager.h
clang::LangOptions
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:53
clang::Stmt::children
child_range children()
Definition: Stmt.cpp:224
clang::Expr
This represents one expression.
Definition: Expr.h:108
BuiltinCheckerRegistration.h
clang
Dataflow Directional Tag Classes.
Definition: CFGReachabilityAnalysis.h:21
clang::ProgramPoint
Definition: ProgramPoint.h:59
clang::PostStmt
Definition: ProgramPoint.h:311
X
X
Add a minimal nested name specifier fixit hint to allow lookup of a tag name from an outer enclosing ...
Definition: SemaDecl.cpp:14780
clang::ProgramPoint::getAs
Optional< T > getAs() const
Convert to the specified ProgramPoint type, returning None if this ProgramPoint is not of the desired...
Definition: ProgramPoint.h:151
CheckerContext.h