1 //== ReturnUndefChecker.cpp -------------------------------------*- 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 file defines ReturnUndefChecker, which is a path-sensitive
11 // check which looks for undefined or garbage values being returned to the
12 // caller.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "ClangSACheckers.h"
17 #include "clang/StaticAnalyzer/Core/Checker.h"
18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
21 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
22 
23 using namespace clang;
24 using namespace ento;
25 
26 namespace {
27 class ReturnUndefChecker :
28     public Checker< check::PreStmt<ReturnStmt> > {
29   mutable OwningPtr<BuiltinBug> BT;
30 public:
31   void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
32 };
33 }
34 
35 void ReturnUndefChecker::checkPreStmt(const ReturnStmt *RS,
36                                       CheckerContext &C) const {
37 
38   const Expr *RetE = RS->getRetValue();
39   if (!RetE)
40     return;
41 
42   if (!C.getState()->getSVal(RetE, C.getLocationContext()).isUndef())
43     return;
44 
45   // "return;" is modeled to evaluate to an UndefinedValue. Allow UndefinedValue
46   // to be returned in functions returning void to support the following pattern:
47   // void foo() {
48   //  return;
49   // }
50   // void test() {
51   //   return foo();
52   // }
53   const StackFrameContext *SFC = C.getStackFrame();
54   QualType RT = CallEvent::getDeclaredResultType(SFC->getDecl());
55   if (!RT.isNull() && RT->isSpecificBuiltinType(BuiltinType::Void))
56     return;
57 
58   ExplodedNode *N = C.generateSink();
59 
60   if (!N)
61     return;
62 
63   if (!BT)
64     BT.reset(new BuiltinBug("Garbage return value",
65                             "Undefined or garbage value returned to caller"));
66 
67   BugReport *report =
68     new BugReport(*BT, BT->getDescription(), N);
69 
70   report->addRange(RetE->getSourceRange());
71   bugreporter::trackNullOrUndefValue(N, RetE, *report);
72 
73   C.EmitReport(report);
74 }
75 
76 void ento::registerReturnUndefChecker(CheckerManager &mgr) {
77   mgr.registerChecker<ReturnUndefChecker>();
78 }
79