1 //==- ExprInspectionChecker.cpp - Used for regression tests ------*- 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 #include "ClangSACheckers.h"
11 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
12 #include "clang/StaticAnalyzer/Core/Checker.h"
13 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
14 #include "llvm/ADT/StringSwitch.h"
15 
16 using namespace clang;
17 using namespace ento;
18 
19 namespace {
20 class ExprInspectionChecker : public Checker< eval::Call > {
21   mutable OwningPtr<BugType> BT;
22 
23   void analyzerEval(const CallExpr *CE, CheckerContext &C) const;
24   void analyzerCheckInlined(const CallExpr *CE, CheckerContext &C) const;
25   void analyzerWarnIfReached(const CallExpr *CE, CheckerContext &C) const;
26   void analyzerCrash(const CallExpr *CE, CheckerContext &C) const;
27 
28   typedef void (ExprInspectionChecker::*FnCheck)(const CallExpr *,
29                                                  CheckerContext &C) const;
30 
31 public:
32   bool evalCall(const CallExpr *CE, CheckerContext &C) const;
33 };
34 }
35 
36 bool ExprInspectionChecker::evalCall(const CallExpr *CE,
37                                      CheckerContext &C) const {
38   // These checks should have no effect on the surrounding environment
39   // (globals should not be invalidated, etc), hence the use of evalCall.
40   FnCheck Handler = llvm::StringSwitch<FnCheck>(C.getCalleeName(CE))
41     .Case("clang_analyzer_eval", &ExprInspectionChecker::analyzerEval)
42     .Case("clang_analyzer_checkInlined",
43           &ExprInspectionChecker::analyzerCheckInlined)
44     .Case("clang_analyzer_crash", &ExprInspectionChecker::analyzerCrash)
45     .Case("clang_analyzer_warnIfReached", &ExprInspectionChecker::analyzerWarnIfReached)
46     .Default(0);
47 
48   if (!Handler)
49     return false;
50 
51   (this->*Handler)(CE, C);
52   return true;
53 }
54 
55 static const char *getArgumentValueString(const CallExpr *CE,
56                                           CheckerContext &C) {
57   if (CE->getNumArgs() == 0)
58     return "Missing assertion argument";
59 
60   ExplodedNode *N = C.getPredecessor();
61   const LocationContext *LC = N->getLocationContext();
62   ProgramStateRef State = N->getState();
63 
64   const Expr *Assertion = CE->getArg(0);
65   SVal AssertionVal = State->getSVal(Assertion, LC);
66 
67   if (AssertionVal.isUndef())
68     return "UNDEFINED";
69 
70   ProgramStateRef StTrue, StFalse;
71   llvm::tie(StTrue, StFalse) =
72     State->assume(AssertionVal.castAs<DefinedOrUnknownSVal>());
73 
74   if (StTrue) {
75     if (StFalse)
76       return "UNKNOWN";
77     else
78       return "TRUE";
79   } else {
80     if (StFalse)
81       return "FALSE";
82     else
83       llvm_unreachable("Invalid constraint; neither true or false.");
84   }
85 }
86 
87 void ExprInspectionChecker::analyzerEval(const CallExpr *CE,
88                                          CheckerContext &C) const {
89   ExplodedNode *N = C.getPredecessor();
90   const LocationContext *LC = N->getLocationContext();
91 
92   // A specific instantiation of an inlined function may have more constrained
93   // values than can generally be assumed. Skip the check.
94   if (LC->getCurrentStackFrame()->getParent() != 0)
95     return;
96 
97   if (!BT)
98     BT.reset(new BugType("Checking analyzer assumptions", "debug"));
99 
100   BugReport *R = new BugReport(*BT, getArgumentValueString(CE, C), N);
101   C.emitReport(R);
102 }
103 
104 void ExprInspectionChecker::analyzerWarnIfReached(const CallExpr *CE,
105                                                   CheckerContext &C) const {
106   ExplodedNode *N = C.getPredecessor();
107 
108   if (!BT)
109     BT.reset(new BugType("Checking analyzer assumptions", "debug"));
110 
111   BugReport *R = new BugReport(*BT, "REACHABLE", N);
112   C.emitReport(R);
113 }
114 
115 void ExprInspectionChecker::analyzerCheckInlined(const CallExpr *CE,
116                                                  CheckerContext &C) const {
117   ExplodedNode *N = C.getPredecessor();
118   const LocationContext *LC = N->getLocationContext();
119 
120   // An inlined function could conceivably also be analyzed as a top-level
121   // function. We ignore this case and only emit a message (TRUE or FALSE)
122   // when we are analyzing it as an inlined function. This means that
123   // clang_analyzer_checkInlined(true) should always print TRUE, but
124   // clang_analyzer_checkInlined(false) should never actually print anything.
125   if (LC->getCurrentStackFrame()->getParent() == 0)
126     return;
127 
128   if (!BT)
129     BT.reset(new BugType("Checking analyzer assumptions", "debug"));
130 
131   BugReport *R = new BugReport(*BT, getArgumentValueString(CE, C), N);
132   C.emitReport(R);
133 }
134 
135 void ExprInspectionChecker::analyzerCrash(const CallExpr *CE,
136                                           CheckerContext &C) const {
137   LLVM_BUILTIN_TRAP;
138 }
139 
140 void ento::registerExprInspectionChecker(CheckerManager &Mgr) {
141   Mgr.registerChecker<ExprInspectionChecker>();
142 }
143 
144