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1 //=== NoReturnFunctionChecker.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 defines NoReturnFunctionChecker, which evaluates functions that do not
11 // return to the caller.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "ClangSACheckers.h"
16 #include "SelectorExtras.h"
17 #include "clang/AST/Attr.h"
18 #include "clang/StaticAnalyzer/Core/Checker.h"
19 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
22 #include "llvm/ADT/StringSwitch.h"
23 #include <cstdarg>
24 
25 using namespace clang;
26 using namespace ento;
27 
28 namespace {
29 
30 class NoReturnFunctionChecker : public Checker< check::PostCall,
31                                                 check::PostObjCMessage > {
32   mutable Selector HandleFailureInFunctionSel;
33   mutable Selector HandleFailureInMethodSel;
34 public:
35   void checkPostCall(const CallEvent &CE, CheckerContext &C) const;
36   void checkPostObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
37 };
38 
39 }
40 
checkPostCall(const CallEvent & CE,CheckerContext & C) const41 void NoReturnFunctionChecker::checkPostCall(const CallEvent &CE,
42                                             CheckerContext &C) const {
43   bool BuildSinks = false;
44 
45   if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(CE.getDecl()))
46     BuildSinks = FD->hasAttr<AnalyzerNoReturnAttr>() || FD->isNoReturn();
47 
48   const Expr *Callee = CE.getOriginExpr();
49   if (!BuildSinks && Callee)
50     BuildSinks = getFunctionExtInfo(Callee->getType()).getNoReturn();
51 
52   if (!BuildSinks && CE.isGlobalCFunction()) {
53     if (const IdentifierInfo *II = CE.getCalleeIdentifier()) {
54       // HACK: Some functions are not marked noreturn, and don't return.
55       //  Here are a few hardwired ones.  If this takes too long, we can
56       //  potentially cache these results.
57       BuildSinks
58         = llvm::StringSwitch<bool>(StringRef(II->getName()))
59             .Case("exit", true)
60             .Case("panic", true)
61             .Case("error", true)
62             .Case("Assert", true)
63             // FIXME: This is just a wrapper around throwing an exception.
64             //  Eventually inter-procedural analysis should handle this easily.
65             .Case("ziperr", true)
66             .Case("assfail", true)
67             .Case("db_error", true)
68             .Case("__assert", true)
69             .Case("__assert2", true)
70             // For the purpose of static analysis, we do not care that
71             //  this MSVC function will return if the user decides to continue.
72             .Case("_wassert", true)
73             .Case("__assert_rtn", true)
74             .Case("__assert_fail", true)
75             .Case("dtrace_assfail", true)
76             .Case("yy_fatal_error", true)
77             .Case("_XCAssertionFailureHandler", true)
78             .Case("_DTAssertionFailureHandler", true)
79             .Case("_TSAssertionFailureHandler", true)
80             .Default(false);
81     }
82   }
83 
84   if (BuildSinks)
85     C.generateSink(C.getState(), C.getPredecessor());
86 }
87 
checkPostObjCMessage(const ObjCMethodCall & Msg,CheckerContext & C) const88 void NoReturnFunctionChecker::checkPostObjCMessage(const ObjCMethodCall &Msg,
89                                                    CheckerContext &C) const {
90   // Check if the method is annotated with analyzer_noreturn.
91   if (const ObjCMethodDecl *MD = Msg.getDecl()) {
92     MD = MD->getCanonicalDecl();
93     if (MD->hasAttr<AnalyzerNoReturnAttr>()) {
94       C.generateSink(C.getState(), C.getPredecessor());
95       return;
96     }
97   }
98 
99   // HACK: This entire check is to handle two messages in the Cocoa frameworks:
100   // -[NSAssertionHandler
101   //    handleFailureInMethod:object:file:lineNumber:description:]
102   // -[NSAssertionHandler
103   //    handleFailureInFunction:file:lineNumber:description:]
104   // Eventually these should be annotated with __attribute__((noreturn)).
105   // Because ObjC messages use dynamic dispatch, it is not generally safe to
106   // assume certain methods can't return. In cases where it is definitely valid,
107   // see if you can mark the methods noreturn or analyzer_noreturn instead of
108   // adding more explicit checks to this method.
109 
110   if (!Msg.isInstanceMessage())
111     return;
112 
113   const ObjCInterfaceDecl *Receiver = Msg.getReceiverInterface();
114   if (!Receiver)
115     return;
116   if (!Receiver->getIdentifier()->isStr("NSAssertionHandler"))
117     return;
118 
119   Selector Sel = Msg.getSelector();
120   switch (Sel.getNumArgs()) {
121   default:
122     return;
123   case 4:
124     lazyInitKeywordSelector(HandleFailureInFunctionSel, C.getASTContext(),
125                             "handleFailureInFunction", "file", "lineNumber",
126                             "description", nullptr);
127     if (Sel != HandleFailureInFunctionSel)
128       return;
129     break;
130   case 5:
131     lazyInitKeywordSelector(HandleFailureInMethodSel, C.getASTContext(),
132                             "handleFailureInMethod", "object", "file",
133                             "lineNumber", "description", nullptr);
134     if (Sel != HandleFailureInMethodSel)
135       return;
136     break;
137   }
138 
139   // If we got here, it's one of the messages we care about.
140   C.generateSink(C.getState(), C.getPredecessor());
141 }
142 
registerNoReturnFunctionChecker(CheckerManager & mgr)143 void ento::registerNoReturnFunctionChecker(CheckerManager &mgr) {
144   mgr.registerChecker<NoReturnFunctionChecker>();
145 }
146