ObjCContainersASTChecker.cpp revision 1efcc42c922204d6797a70d90d3c350882f3c098 
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/Analysis/AnalysisContext.h"
16#include "clang/AST/StmtVisitor.h"
17#include "clang/Basic/TargetInfo.h"
18#include "clang/StaticAnalyzer/Core/Checker.h"
19#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
21#include "llvm/Support/raw_ostream.h"
22
23using namespace clang;
24using namespace ento;
25
26namespace {
27class WalkAST : public StmtVisitor<WalkAST> {
28  BugReporter &BR;
29  AnalysisDeclContext* AC;
30  ASTContext &ASTC;
31  uint64_t PtrWidth;
32
33  static const unsigned InvalidArgIndex = UINT_MAX;
34
35  /// Check if the type has pointer size (very conservative).
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.
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
74public:
75  WalkAST(BugReporter &br, AnalysisDeclContext* ac)
76  : BR(br), AC(ac), ASTC(AC->getASTContext()),
77    PtrWidth(ASTC.getTargetInfo().getPointerWidth(0)) {}
78
79  // Statement visitor methods.
80  void VisitChildren(Stmt *S);
81  void VisitStmt(Stmt *S) { VisitChildren(S); }
82  void VisitCallExpr(CallExpr *CE);
83};
84} // end anonymous namespace
85
86static 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
98void WalkAST::VisitCallExpr(CallExpr *CE) {
99  StringRef Name = getCalleeName(CE);
100  if (Name.empty())
101    return;
102
103  const Expr *Arg = 0;
104  unsigned ArgNum = InvalidArgIndex;
105
106  if (Name.equals("CFArrayCreate") || Name.equals("CFSetCreate")) {
107    ArgNum = 1;
108    Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
109    if (hasPointerToPointerSizedType(Arg))
110        return;
111  }
112
113  if (Arg == 0 && Name.equals("CFDictionaryCreate")) {
114    // Check first argument.
115    ArgNum = 1;
116    Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
117    if (hasPointerToPointerSizedType(Arg)) {
118      // Check second argument.
119      ArgNum = 2;
120      Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
121      if (hasPointerToPointerSizedType(Arg))
122        // Both are good, return.
123        return;
124    }
125  }
126
127  if (ArgNum != InvalidArgIndex) {
128    assert(ArgNum == 1 || ArgNum == 2);
129
130    llvm::SmallString<256> BufName;
131    llvm::raw_svector_ostream OsName(BufName);
132    assert(ArgNum == 1 || ArgNum == 2);
133    OsName << " Invalid use of '" << Name << "'" ;
134
135    llvm::SmallString<256> Buf;
136    llvm::raw_svector_ostream Os(Buf);
137    Os << " The "<< ((ArgNum == 1) ? "first" : "second") << " argument to '"
138        << Name << "' must be a C array of pointer-sized values, not '"
139        << Arg->getType().getAsString() << "'";
140
141    SourceRange R = Arg->getSourceRange();
142    PathDiagnosticLocation CELoc =
143        PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
144    BR.EmitBasicReport(OsName.str(), "Core Foundation/Objective-C",
145                       Os.str(), CELoc, &R, 1);
146  }
147
148  // Recurse and check children.
149  VisitChildren(CE);
150}
151
152void WalkAST::VisitChildren(Stmt *S) {
153  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
154    if (Stmt *child = *I)
155      Visit(child);
156}
157
158namespace {
159class ObjCContainersASTChecker : public Checker<check::ASTCodeBody> {
160public:
161
162  void checkASTCodeBody(const Decl *D, AnalysisManager& Mgr,
163                        BugReporter &BR) const {
164    WalkAST walker(BR, Mgr.getAnalysisDeclContext(D));
165    walker.Visit(D->getBody());
166  }
167};
168}
169
170void ento::registerObjCContainersASTChecker(CheckerManager &mgr) {
171  mgr.registerChecker<ObjCContainersASTChecker>();
172}
173