1 //== ObjCContainersASTChecker.cpp - CoreFoundation containers API *- 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 // An AST checker that looks for common pitfalls when using 'CFArray',
11 // 'CFDictionary', 'CFSet' APIs.
12 //
13 //===----------------------------------------------------------------------===//
14 #include "ClangSACheckers.h"
15 #include "clang/AST/StmtVisitor.h"
16 #include "clang/Analysis/AnalysisContext.h"
17 #include "clang/Basic/TargetInfo.h"
18 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
19 #include "clang/StaticAnalyzer/Core/Checker.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
21 #include "llvm/ADT/SmallString.h"
22 #include "llvm/Support/raw_ostream.h"
23
24 using namespace clang;
25 using namespace ento;
26
27 namespace {
28 class WalkAST : public StmtVisitor<WalkAST> {
29 BugReporter &BR;
30 const CheckerBase *Checker;
31 AnalysisDeclContext* AC;
32 ASTContext &ASTC;
33 uint64_t PtrWidth;
34
35 /// Check if the type has pointer size (very conservative).
isPointerSize(const Type * T)36 inline bool isPointerSize(const Type *T) {
37 if (!T)
38 return true;
39 if (T->isIncompleteType())
40 return true;
41 return (ASTC.getTypeSize(T) == PtrWidth);
42 }
43
44 /// Check if the type is a pointer/array to pointer sized values.
hasPointerToPointerSizedType(const Expr * E)45 inline bool hasPointerToPointerSizedType(const Expr *E) {
46 QualType T = E->getType();
47
48 // The type could be either a pointer or array.
49 const Type *TP = T.getTypePtr();
50 QualType PointeeT = TP->getPointeeType();
51 if (!PointeeT.isNull()) {
52 // If the type is a pointer to an array, check the size of the array
53 // elements. To avoid false positives coming from assumption that the
54 // values x and &x are equal when x is an array.
55 if (const Type *TElem = PointeeT->getArrayElementTypeNoTypeQual())
56 if (isPointerSize(TElem))
57 return true;
58
59 // Else, check the pointee size.
60 return isPointerSize(PointeeT.getTypePtr());
61 }
62
63 if (const Type *TElem = TP->getArrayElementTypeNoTypeQual())
64 return isPointerSize(TElem);
65
66 // The type must be an array/pointer type.
67
68 // This could be a null constant, which is allowed.
69 if (E->isNullPointerConstant(ASTC, Expr::NPC_ValueDependentIsNull))
70 return true;
71 return false;
72 }
73
74 public:
WalkAST(BugReporter & br,const CheckerBase * checker,AnalysisDeclContext * ac)75 WalkAST(BugReporter &br, const CheckerBase *checker, AnalysisDeclContext *ac)
76 : BR(br), Checker(checker), AC(ac), ASTC(AC->getASTContext()),
77 PtrWidth(ASTC.getTargetInfo().getPointerWidth(0)) {}
78
79 // Statement visitor methods.
80 void VisitChildren(Stmt *S);
VisitStmt(Stmt * S)81 void VisitStmt(Stmt *S) { VisitChildren(S); }
82 void VisitCallExpr(CallExpr *CE);
83 };
84 } // end anonymous namespace
85
getCalleeName(CallExpr * CE)86 static StringRef getCalleeName(CallExpr *CE) {
87 const FunctionDecl *FD = CE->getDirectCallee();
88 if (!FD)
89 return StringRef();
90
91 IdentifierInfo *II = FD->getIdentifier();
92 if (!II) // if no identifier, not a simple C function
93 return StringRef();
94
95 return II->getName();
96 }
97
VisitCallExpr(CallExpr * CE)98 void WalkAST::VisitCallExpr(CallExpr *CE) {
99 StringRef Name = getCalleeName(CE);
100 if (Name.empty())
101 return;
102
103 const Expr *Arg = nullptr;
104 unsigned ArgNum;
105
106 if (Name.equals("CFArrayCreate") || Name.equals("CFSetCreate")) {
107 if (CE->getNumArgs() != 4)
108 return;
109 ArgNum = 1;
110 Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
111 if (hasPointerToPointerSizedType(Arg))
112 return;
113 } else if (Name.equals("CFDictionaryCreate")) {
114 if (CE->getNumArgs() != 6)
115 return;
116 // Check first argument.
117 ArgNum = 1;
118 Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
119 if (hasPointerToPointerSizedType(Arg)) {
120 // Check second argument.
121 ArgNum = 2;
122 Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
123 if (hasPointerToPointerSizedType(Arg))
124 // Both are good, return.
125 return;
126 }
127 }
128
129 if (Arg) {
130 assert(ArgNum == 1 || ArgNum == 2);
131
132 SmallString<64> BufName;
133 llvm::raw_svector_ostream OsName(BufName);
134 OsName << " Invalid use of '" << Name << "'" ;
135
136 SmallString<256> Buf;
137 llvm::raw_svector_ostream Os(Buf);
138 // Use "second" and "third" since users will expect 1-based indexing
139 // for parameter names when mentioned in prose.
140 Os << " The "<< ((ArgNum == 1) ? "second" : "third") << " argument to '"
141 << Name << "' must be a C array of pointer-sized values, not '"
142 << Arg->getType().getAsString() << "'";
143
144 PathDiagnosticLocation CELoc =
145 PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
146 BR.EmitBasicReport(AC->getDecl(), Checker, OsName.str(),
147 categories::CoreFoundationObjectiveC, Os.str(), CELoc,
148 Arg->getSourceRange());
149 }
150
151 // Recurse and check children.
152 VisitChildren(CE);
153 }
154
VisitChildren(Stmt * S)155 void WalkAST::VisitChildren(Stmt *S) {
156 for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
157 if (Stmt *child = *I)
158 Visit(child);
159 }
160
161 namespace {
162 class ObjCContainersASTChecker : public Checker<check::ASTCodeBody> {
163 public:
164
checkASTCodeBody(const Decl * D,AnalysisManager & Mgr,BugReporter & BR) const165 void checkASTCodeBody(const Decl *D, AnalysisManager& Mgr,
166 BugReporter &BR) const {
167 WalkAST walker(BR, this, Mgr.getAnalysisDeclContext(D));
168 walker.Visit(D->getBody());
169 }
170 };
171 }
172
registerObjCContainersASTChecker(CheckerManager & mgr)173 void ento::registerObjCContainersASTChecker(CheckerManager &mgr) {
174 mgr.registerChecker<ObjCContainersASTChecker>();
175 }
176