UndefinedAssignmentChecker.cpp revision 651f13cea278ec967336033dd032faef0e9fc2ec 
1//===--- UndefinedAssignmentChecker.h ---------------------------*- C++ -*--==//
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// This defines UndefinedAssignmentChecker, a builtin check in ExprEngine that
11// checks for assigning undefined values.
12//
13//===----------------------------------------------------------------------===//
14
15#include "ClangSACheckers.h"
16#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
17#include "clang/StaticAnalyzer/Core/Checker.h"
18#include "clang/StaticAnalyzer/Core/CheckerManager.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20
21using namespace clang;
22using namespace ento;
23
24namespace {
25class UndefinedAssignmentChecker
26  : public Checker<check::Bind> {
27  mutable std::unique_ptr<BugType> BT;
28
29public:
30  void checkBind(SVal location, SVal val, const Stmt *S,
31                 CheckerContext &C) const;
32};
33}
34
35void UndefinedAssignmentChecker::checkBind(SVal location, SVal val,
36                                           const Stmt *StoreE,
37                                           CheckerContext &C) const {
38  if (!val.isUndef())
39    return;
40
41  // Do not report assignments of uninitialized values inside swap functions.
42  // This should allow to swap partially uninitialized structs
43  // (radar://14129997)
44  if (const FunctionDecl *EnclosingFunctionDecl =
45      dyn_cast<FunctionDecl>(C.getStackFrame()->getDecl()))
46    if (C.getCalleeName(EnclosingFunctionDecl) == "swap")
47      return;
48
49  ExplodedNode *N = C.generateSink();
50
51  if (!N)
52    return;
53
54  const char *str = "Assigned value is garbage or undefined";
55
56  if (!BT)
57    BT.reset(new BuiltinBug(this, str));
58
59  // Generate a report for this bug.
60  const Expr *ex = 0;
61
62  while (StoreE) {
63    if (const BinaryOperator *B = dyn_cast<BinaryOperator>(StoreE)) {
64      if (B->isCompoundAssignmentOp()) {
65        ProgramStateRef state = C.getState();
66        if (state->getSVal(B->getLHS(), C.getLocationContext()).isUndef()) {
67          str = "The left expression of the compound assignment is an "
68                "uninitialized value. The computed value will also be garbage";
69          ex = B->getLHS();
70          break;
71        }
72      }
73
74      ex = B->getRHS();
75      break;
76    }
77
78    if (const DeclStmt *DS = dyn_cast<DeclStmt>(StoreE)) {
79      const VarDecl *VD = dyn_cast<VarDecl>(DS->getSingleDecl());
80      ex = VD->getInit();
81    }
82
83    break;
84  }
85
86  BugReport *R = new BugReport(*BT, str, N);
87  if (ex) {
88    R->addRange(ex->getSourceRange());
89    bugreporter::trackNullOrUndefValue(N, ex, *R);
90  }
91  C.emitReport(R);
92}
93
94void ento::registerUndefinedAssignmentChecker(CheckerManager &mgr) {
95  mgr.registerChecker<UndefinedAssignmentChecker>();
96}
97