ObjCContainersASTChecker.cpp revision 31b71f3097a338315a144067dde5b160c4e44fc9 
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
24using namespace clang;
25using namespace ento;
26
27namespace {
28class WalkAST : public StmtVisitor<WalkAST> {
29  BugReporter &BR;
30  AnalysisDeclContext* AC;
31  ASTContext &ASTC;
32  uint64_t PtrWidth;
33
34  /// Check if the type has pointer size (very conservative).
35  inline bool isPointerSize(const Type *T) {
36    if (!T)
37      return true;
38    if (T->isIncompleteType())
39      return true;
40    return (ASTC.getTypeSize(T) == PtrWidth);
41  }
42
43  /// Check if the type is a pointer/array to pointer sized values.
44  inline bool hasPointerToPointerSizedType(const Expr *E) {
45    QualType T = E->getType();
46
47    // The type could be either a pointer or array.
48    const Type *TP = T.getTypePtr();
49    QualType PointeeT = TP->getPointeeType();
50    if (!PointeeT.isNull()) {
51      // If the type is a pointer to an array, check the size of the array
52      // elements. To avoid false positives coming from assumption that the
53      // values x and &x are equal when x is an array.
54      if (const Type *TElem = PointeeT->getArrayElementTypeNoTypeQual())
55        if (isPointerSize(TElem))
56          return true;
57
58      // Else, check the pointee size.
59      return isPointerSize(PointeeT.getTypePtr());
60    }
61
62    if (const Type *TElem = TP->getArrayElementTypeNoTypeQual())
63      return isPointerSize(TElem);
64
65    // The type must be an array/pointer type.
66
67    // This could be a null constant, which is allowed.
68    if (E->isNullPointerConstant(ASTC, Expr::NPC_ValueDependentIsNull))
69      return true;
70    return false;
71  }
72
73public:
74  WalkAST(BugReporter &br, AnalysisDeclContext* ac)
75  : BR(br), AC(ac), ASTC(AC->getASTContext()),
76    PtrWidth(ASTC.getTargetInfo().getPointerWidth(0)) {}
77
78  // Statement visitor methods.
79  void VisitChildren(Stmt *S);
80  void VisitStmt(Stmt *S) { VisitChildren(S); }
81  void VisitCallExpr(CallExpr *CE);
82};
83} // end anonymous namespace
84
85static StringRef getCalleeName(CallExpr *CE) {
86  const FunctionDecl *FD = CE->getDirectCallee();
87  if (!FD)
88    return StringRef();
89
90  IdentifierInfo *II = FD->getIdentifier();
91  if (!II)   // if no identifier, not a simple C function
92    return StringRef();
93
94  return II->getName();
95}
96
97void WalkAST::VisitCallExpr(CallExpr *CE) {
98  StringRef Name = getCalleeName(CE);
99  if (Name.empty())
100    return;
101
102  const Expr *Arg = 0;
103  unsigned ArgNum;
104
105  if (Name.equals("CFArrayCreate") || Name.equals("CFSetCreate")) {
106    if (CE->getNumArgs() != 4)
107      return;
108    ArgNum = 1;
109    Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
110    if (hasPointerToPointerSizedType(Arg))
111        return;
112  } else if (Name.equals("CFDictionaryCreate")) {
113    if (CE->getNumArgs() != 6)
114      return;
115    // Check first argument.
116    ArgNum = 1;
117    Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
118    if (hasPointerToPointerSizedType(Arg)) {
119      // Check second argument.
120      ArgNum = 2;
121      Arg = CE->getArg(ArgNum)->IgnoreParenCasts();
122      if (hasPointerToPointerSizedType(Arg))
123        // Both are good, return.
124        return;
125    }
126  }
127
128  if (Arg) {
129    assert(ArgNum == 1 || ArgNum == 2);
130
131    SmallString<64> BufName;
132    llvm::raw_svector_ostream OsName(BufName);
133    OsName << " Invalid use of '" << Name << "'" ;
134
135    SmallString<256> Buf;
136    llvm::raw_svector_ostream Os(Buf);
137    // Use "second" and "third" since users will expect 1-based indexing
138    // for parameter names when mentioned in prose.
139    Os << " The "<< ((ArgNum == 1) ? "second" : "third") << " argument to '"
140        << Name << "' must be a C array of pointer-sized values, not '"
141        << Arg->getType().getAsString() << "'";
142
143    PathDiagnosticLocation CELoc =
144        PathDiagnosticLocation::createBegin(CE, BR.getSourceManager(), AC);
145    BR.EmitBasicReport(AC->getDecl(),
146                       OsName.str(), categories::CoreFoundationObjectiveC,
147                       Os.str(), CELoc, Arg->getSourceRange());
148  }
149
150  // Recurse and check children.
151  VisitChildren(CE);
152}
153
154void WalkAST::VisitChildren(Stmt *S) {
155  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
156    if (Stmt *child = *I)
157      Visit(child);
158}
159
160namespace {
161class ObjCContainersASTChecker : public Checker<check::ASTCodeBody> {
162public:
163
164  void checkASTCodeBody(const Decl *D, AnalysisManager& Mgr,
165                        BugReporter &BR) const {
166    WalkAST walker(BR, Mgr.getAnalysisDeclContext(D));
167    walker.Visit(D->getBody());
168  }
169};
170}
171
172void ento::registerObjCContainersASTChecker(CheckerManager &mgr) {
173  mgr.registerChecker<ObjCContainersASTChecker>();
174}
175