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   if (const CallExpr *CExpr = dyn_cast_or_null<CallExpr>(CE.getOriginExpr());
48       CExpr && !BuildSinks) {
49     if (const Expr *C = CExpr->getCallee())
50       BuildSinks = getFunctionExtInfo(C->getType()).getNoReturn();
51   }
52 
53   if (!BuildSinks && CE.isGlobalCFunction()) {
54     if (const IdentifierInfo *II = CE.getCalleeIdentifier()) {
55       // HACK: Some functions are not marked noreturn, and don't return.
56       //  Here are a few hardwired ones.  If this takes too long, we can
57       //  potentially cache these results.
58       BuildSinks
59         = llvm::StringSwitch<bool>(StringRef(II->getName()))
60             .Case("exit", true)
61             .Case("panic", true)
62             .Case("error", true)
63             .Case("Assert", true)
64             // FIXME: This is just a wrapper around throwing an exception.
65             //  Eventually inter-procedural analysis should handle this easily.
66             .Case("ziperr", true)
67             .Case("assfail", true)
68             .Case("db_error", true)
69             .Case("__assert", true)
70             .Case("__assert2", true)
71             // For the purpose of static analysis, we do not care that
72             //  this MSVC function will return if the user decides to continue.
73             .Case("_wassert", true)
74             .Case("__assert_rtn", true)
75             .Case("__assert_fail", true)
76             .Case("dtrace_assfail", true)
77             .Case("yy_fatal_error", true)
78             .Case("_XCAssertionFailureHandler", true)
79             .Case("_DTAssertionFailureHandler", true)
80             .Case("_TSAssertionFailureHandler", true)
81             .Default(false);
82     }
83   }
84 
85   if (BuildSinks)
86     C.generateSink(C.getState(), C.getPredecessor());
87 }
88 
89 void NoReturnFunctionChecker::checkPostObjCMessage(const ObjCMethodCall &Msg,
90                                                    CheckerContext &C) const {
91   // Check if the method is annotated with analyzer_noreturn.
92   if (const ObjCMethodDecl *MD = Msg.getDecl()) {
93     MD = MD->getCanonicalDecl();
94     if (MD->hasAttr<AnalyzerNoReturnAttr>()) {
95       C.generateSink(C.getState(), C.getPredecessor());
96       return;
97     }
98   }
99 
100   // HACK: This entire check is to handle two messages in the Cocoa frameworks:
101   // -[NSAssertionHandler
102   //    handleFailureInMethod:object:file:lineNumber:description:]
103   // -[NSAssertionHandler
104   //    handleFailureInFunction:file:lineNumber:description:]
105   // Eventually these should be annotated with __attribute__((noreturn)).
106   // Because ObjC messages use dynamic dispatch, it is not generally safe to
107   // assume certain methods can't return. In cases where it is definitely valid,
108   // see if you can mark the methods noreturn or analyzer_noreturn instead of
109   // adding more explicit checks to this method.
110 
111   if (!Msg.isInstanceMessage())
112     return;
113 
114   const ObjCInterfaceDecl *Receiver = Msg.getReceiverInterface();
115   if (!Receiver)
116     return;
117   if (!Receiver->getIdentifier()->isStr("NSAssertionHandler"))
118     return;
119 
120   Selector Sel = Msg.getSelector();
121   switch (Sel.getNumArgs()) {
122   default:
123     return;
124   case 4:
125     lazyInitKeywordSelector(HandleFailureInFunctionSel, C.getASTContext(),
126                             "handleFailureInFunction", "file", "lineNumber",
127                             "description");
128     if (Sel != HandleFailureInFunctionSel)
129       return;
130     break;
131   case 5:
132     lazyInitKeywordSelector(HandleFailureInMethodSel, C.getASTContext(),
133                             "handleFailureInMethod", "object", "file",
134                             "lineNumber", "description");
135     if (Sel != HandleFailureInMethodSel)
136       return;
137     break;
138   }
139 
140   // If we got here, it's one of the messages we care about.
141   C.generateSink(C.getState(), C.getPredecessor());
142 }
143 
144 void ento::registerNoReturnFunctionChecker(CheckerManager &mgr) {
145   mgr.registerChecker<NoReturnFunctionChecker>();
146 }
147 
148 bool ento::shouldRegisterNoReturnFunctionChecker(const CheckerManager &mgr) {
149   return true;
150 }
151