CheckSizeofPointer.cpp revision ec8605f1d7ec846dbf51047bfd5c56d32d1ff91c 
1//==- CheckSizeofPointer.cpp - Check for sizeof on pointers ------*- 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//  This file defines a check for unintended use of sizeof() on pointer
11//  expressions.
12//
13//===----------------------------------------------------------------------===//
14
15#include "ClangSACheckers.h"
16#include "clang/StaticAnalyzer/Core/Checker.h"
17#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
18#include "clang/AST/StmtVisitor.h"
19
20using namespace clang;
21using namespace ento;
22
23namespace {
24class WalkAST : public StmtVisitor<WalkAST> {
25  BugReporter &BR;
26
27public:
28  WalkAST(BugReporter &br) : BR(br) {}
29  void VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E);
30  void VisitStmt(Stmt *S) { VisitChildren(S); }
31  void VisitChildren(Stmt *S);
32};
33}
34
35void WalkAST::VisitChildren(Stmt *S) {
36  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
37    if (Stmt *child = *I)
38      Visit(child);
39}
40
41// CWE-467: Use of sizeof() on a Pointer Type
42void WalkAST::VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E) {
43  if (!E->isSizeOf())
44    return;
45
46  // If an explicit type is used in the code, usually the coder knows what he is
47  // doing.
48  if (E->isArgumentType())
49    return;
50
51  QualType T = E->getTypeOfArgument();
52  if (T->isPointerType()) {
53
54    // Many false positives have the form 'sizeof *p'. This is reasonable
55    // because people know what they are doing when they intentionally
56    // dereference the pointer.
57    Expr *ArgEx = E->getArgumentExpr();
58    if (!isa<DeclRefExpr>(ArgEx->IgnoreParens()))
59      return;
60
61    SourceRange R = ArgEx->getSourceRange();
62    BR.EmitBasicReport("Potential unintended use of sizeof() on pointer type",
63                       "Logic",
64                       "The code calls sizeof() on a pointer type. "
65                       "This can produce an unexpected result.",
66                       E->getLocStart(), &R, 1);
67  }
68}
69
70//===----------------------------------------------------------------------===//
71// SizeofPointerChecker
72//===----------------------------------------------------------------------===//
73
74namespace {
75class SizeofPointerChecker : public Checker<check::ASTCodeBody> {
76public:
77  void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
78                        BugReporter &BR) const {
79    WalkAST walker(BR);
80    walker.Visit(D->getBody());
81  }
82};
83}
84
85void ento::registerSizeofPointerChecker(CheckerManager &mgr) {
86  mgr.registerChecker<SizeofPointerChecker>();
87}
88