1 //=== NoReturnFunctionChecker.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 defines NoReturnFunctionChecker, which evaluates functions that do not
10 // return to the caller.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
15 #include "clang/AST/Attr.h"
16 #include "clang/Analysis/SelectorExtras.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 "llvm/ADT/StringSwitch.h"
22 #include <cstdarg>
23 
24 using namespace clang;
25 using namespace ento;
26 
27 namespace {
28 
29 class NoReturnFunctionChecker : public Checker< check::PostCall,
30                                                 check::PostObjCMessage > {
31   mutable Selector HandleFailureInFunctionSel;
32   mutable Selector HandleFailureInMethodSel;
33 public:
34   void checkPostCall(const CallEvent &CE, CheckerContext &C) const;
35   void checkPostObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
36 };
37 
38 }
39 
40 void NoReturnFunctionChecker::checkPostCall(const CallEvent &CE,
41                                             CheckerContext &C) const {
42   bool BuildSinks = false;
43 
44   if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(CE.getDecl()))
45     BuildSinks = FD->hasAttr<AnalyzerNoReturnAttr>() || FD->isNoReturn();
46 
47   const Expr *Callee = CE.getOriginExpr();
48   if (!BuildSinks && Callee)
49     BuildSinks = getFunctionExtInfo(Callee->getType()).getNoReturn();
50 
51   if (!BuildSinks && CE.isGlobalCFunction()) {
52     if (const IdentifierInfo *II = CE.getCalleeIdentifier()) {
53       // HACK: Some functions are not marked noreturn, and don't return.
54       //  Here are a few hardwired ones.  If this takes too long, we can
55       //  potentially cache these results.
56       BuildSinks
57         = llvm::StringSwitch<bool>(StringRef(II->getName()))
58             .Case("exit", true)
59             .Case("panic", true)
60             .Case("error", true)
61             .Case("Assert", true)
62             // FIXME: This is just a wrapper around throwing an exception.
63             //  Eventually inter-procedural analysis should handle this easily.
64             .Case("ziperr", true)
65             .Case("assfail", true)
66             .Case("db_error", true)
67             .Case("__assert", true)
68             .Case("__assert2", true)
69             // For the purpose of static analysis, we do not care that
70             //  this MSVC function will return if the user decides to continue.
71             .Case("_wassert", true)
72             .Case("__assert_rtn", true)
73             .Case("__assert_fail", true)
74             .Case("dtrace_assfail", true)
75             .Case("yy_fatal_error", true)
76             .Case("_XCAssertionFailureHandler", true)
77             .Case("_DTAssertionFailureHandler", true)
78             .Case("_TSAssertionFailureHandler", true)
79             .Default(false);
80     }
81   }
82 
83   if (BuildSinks)
84     C.generateSink(C.getState(), C.getPredecessor());
85 }
86 
87 void NoReturnFunctionChecker::checkPostObjCMessage(const ObjCMethodCall &Msg,
88                                                    CheckerContext &C) const {
89   // Check if the method is annotated with analyzer_noreturn.
90   if (const ObjCMethodDecl *MD = Msg.getDecl()) {
91     MD = MD->getCanonicalDecl();
92     if (MD->hasAttr<AnalyzerNoReturnAttr>()) {
93       C.generateSink(C.getState(), C.getPredecessor());
94       return;
95     }
96   }
97 
98   // HACK: This entire check is to handle two messages in the Cocoa frameworks:
99   // -[NSAssertionHandler
100   //    handleFailureInMethod:object:file:lineNumber:description:]
101   // -[NSAssertionHandler
102   //    handleFailureInFunction:file:lineNumber:description:]
103   // Eventually these should be annotated with __attribute__((noreturn)).
104   // Because ObjC messages use dynamic dispatch, it is not generally safe to
105   // assume certain methods can't return. In cases where it is definitely valid,
106   // see if you can mark the methods noreturn or analyzer_noreturn instead of
107   // adding more explicit checks to this method.
108 
109   if (!Msg.isInstanceMessage())
110     return;
111 
112   const ObjCInterfaceDecl *Receiver = Msg.getReceiverInterface();
113   if (!Receiver)
114     return;
115   if (!Receiver->getIdentifier()->isStr("NSAssertionHandler"))
116     return;
117 
118   Selector Sel = Msg.getSelector();
119   switch (Sel.getNumArgs()) {
120   default:
121     return;
122   case 4:
123     lazyInitKeywordSelector(HandleFailureInFunctionSel, C.getASTContext(),
124                             "handleFailureInFunction", "file", "lineNumber",
125                             "description");
126     if (Sel != HandleFailureInFunctionSel)
127       return;
128     break;
129   case 5:
130     lazyInitKeywordSelector(HandleFailureInMethodSel, C.getASTContext(),
131                             "handleFailureInMethod", "object", "file",
132                             "lineNumber", "description");
133     if (Sel != HandleFailureInMethodSel)
134       return;
135     break;
136   }
137 
138   // If we got here, it's one of the messages we care about.
139   C.generateSink(C.getState(), C.getPredecessor());
140 }
141 
142 void ento::registerNoReturnFunctionChecker(CheckerManager &mgr) {
143   mgr.registerChecker<NoReturnFunctionChecker>();
144 }
145 
146 bool ento::shouldRegisterNoReturnFunctionChecker(const LangOptions &LO) {
147   return true;
148 }
149