From 39fcc9a984e2820e4ea0fa2ac4abd17d9f3a31df Mon Sep 17 00:00:00 2001
From: dim <dim@FreeBSD.org>
Date: Sun, 20 Feb 2011 13:06:31 +0000
Subject: Vendor import of clang trunk r126079:
http://llvm.org/svn/llvm-project/cfe/trunk@126079
---
lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp | 205 +++++++++++++++++++++
1 file changed, 205 insertions(+)
create mode 100644 lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp
(limited to 'lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp')
diff --git a/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp b/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp
new file mode 100644
index 0000000..606ac4a
--- /dev/null
+++ b/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp
@@ -0,0 +1,205 @@
+//== NullDerefChecker.cpp - Null dereference checker ------------*- C++ -*--==//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This defines NullDerefChecker, a builtin check in ExprEngine that performs
+// checks for null pointers at loads and stores.
+//
+//===----------------------------------------------------------------------===//
+
+#include "InternalChecks.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Checkers/DereferenceChecker.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/Checker.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class DereferenceChecker : public Checker {
+ BuiltinBug *BT_null;
+ BuiltinBug *BT_undef;
+ llvm::SmallVector<ExplodedNode*, 2> ImplicitNullDerefNodes;
+public:
+ DereferenceChecker() : BT_null(0), BT_undef(0) {}
+ static void *getTag() { static int tag = 0; return &tag; }
+ void visitLocation(CheckerContext &C, const Stmt *S, SVal location,
+ bool isLoad);
+
+ std::pair<ExplodedNode * const*, ExplodedNode * const*>
+ getImplicitNodes() const {
+ return std::make_pair(ImplicitNullDerefNodes.data(),
+ ImplicitNullDerefNodes.data() +
+ ImplicitNullDerefNodes.size());
+ }
+ void AddDerefSource(llvm::raw_ostream &os,
+ llvm::SmallVectorImpl<SourceRange> &Ranges,
+ const Expr *Ex, bool loadedFrom = false);
+};
+} // end anonymous namespace
+
+void ento::RegisterDereferenceChecker(ExprEngine &Eng) {
+ Eng.registerCheck(new DereferenceChecker());
+}
+
+std::pair<ExplodedNode * const *, ExplodedNode * const *>
+ento::GetImplicitNullDereferences(ExprEngine &Eng) {
+ DereferenceChecker *checker = Eng.getChecker<DereferenceChecker>();
+ if (!checker)
+ return std::make_pair((ExplodedNode * const *) 0,
+ (ExplodedNode * const *) 0);
+ return checker->getImplicitNodes();
+}
+
+void DereferenceChecker::AddDerefSource(llvm::raw_ostream &os,
+ llvm::SmallVectorImpl<SourceRange> &Ranges,
+ const Expr *Ex,
+ bool loadedFrom) {
+ Ex = Ex->IgnoreParenLValueCasts();
+ switch (Ex->getStmtClass()) {
+ default:
+ return;
+ case Stmt::DeclRefExprClass: {
+ const DeclRefExpr *DR = cast<DeclRefExpr>(Ex);
+ if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
+ os << " (" << (loadedFrom ? "loaded from" : "from")
+ << " variable '" << VD->getName() << "')";
+ Ranges.push_back(DR->getSourceRange());
+ }
+ return;
+ }
+ case Stmt::MemberExprClass: {
+ const MemberExpr *ME = cast<MemberExpr>(Ex);
+ os << " (" << (loadedFrom ? "loaded from" : "via")
+ << " field '" << ME->getMemberNameInfo() << "')";
+ SourceLocation L = ME->getMemberLoc();
+ Ranges.push_back(SourceRange(L, L));
+ break;
+ }
+ }
+}
+
+void DereferenceChecker::visitLocation(CheckerContext &C, const Stmt *S,
+ SVal l, bool isLoad) {
+ // Check for dereference of an undefined value.
+ if (l.isUndef()) {
+ if (ExplodedNode *N = C.generateSink()) {
+ if (!BT_undef)
+ BT_undef = new BuiltinBug("Dereference of undefined pointer value");
+
+ EnhancedBugReport *report =
+ new EnhancedBugReport(*BT_undef, BT_undef->getDescription(), N);
+ report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue,
+ bugreporter::GetDerefExpr(N));
+ C.EmitReport(report);
+ }
+ return;
+ }
+
+ DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(l);
+
+ // Check for null dereferences.
+ if (!isa<Loc>(location))
+ return;
+
+ const GRState *state = C.getState();
+ const GRState *notNullState, *nullState;
+ llvm::tie(notNullState, nullState) = state->assume(location);
+
+ // The explicit NULL case.
+ if (nullState) {
+ if (!notNullState) {
+ // Generate an error node.
+ ExplodedNode *N = C.generateSink(nullState);
+ if (!N)
+ return;
+
+ // We know that 'location' cannot be non-null. This is what
+ // we call an "explicit" null dereference.
+ if (!BT_null)
+ BT_null = new BuiltinBug("Dereference of null pointer");
+
+ llvm::SmallString<100> buf;
+ llvm::SmallVector<SourceRange, 2> Ranges;
+
+ // Walk through lvalue casts to get the original expression
+ // that syntactically caused the load.
+ if (const Expr *expr = dyn_cast<Expr>(S))
+ S = expr->IgnoreParenLValueCasts();
+
+ switch (S->getStmtClass()) {
+ case Stmt::ArraySubscriptExprClass: {
+ llvm::raw_svector_ostream os(buf);
+ os << "Array access";
+ const ArraySubscriptExpr *AE = cast<ArraySubscriptExpr>(S);
+ AddDerefSource(os, Ranges, AE->getBase()->IgnoreParenCasts());
+ os << " results in a null pointer dereference";
+ break;
+ }
+ case Stmt::UnaryOperatorClass: {
+ llvm::raw_svector_ostream os(buf);
+ os << "Dereference of null pointer";
+ const UnaryOperator *U = cast<UnaryOperator>(S);
+ AddDerefSource(os, Ranges, U->getSubExpr()->IgnoreParens(), true);
+ break;
+ }
+ case Stmt::MemberExprClass: {
+ const MemberExpr *M = cast<MemberExpr>(S);
+ if (M->isArrow()) {
+ llvm::raw_svector_ostream os(buf);
+ os << "Access to field '" << M->getMemberNameInfo()
+ << "' results in a dereference of a null pointer";
+ AddDerefSource(os, Ranges, M->getBase()->IgnoreParenCasts(), true);
+ }
+ break;
+ }
+ case Stmt::ObjCIvarRefExprClass: {
+ const ObjCIvarRefExpr *IV = cast<ObjCIvarRefExpr>(S);
+ if (const DeclRefExpr *DR =
+ dyn_cast<DeclRefExpr>(IV->getBase()->IgnoreParenCasts())) {
+ if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
+ llvm::raw_svector_ostream os(buf);
+ os << "Instance variable access (via '" << VD->getName()
+ << "') results in a null pointer dereference";
+ }
+ }
+ Ranges.push_back(IV->getSourceRange());
+ break;
+ }
+ default:
+ break;
+ }
+
+ EnhancedBugReport *report =
+ new EnhancedBugReport(*BT_null,
+ buf.empty() ? BT_null->getDescription():buf.str(),
+ N);
+
+ report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue,
+ bugreporter::GetDerefExpr(N));
+
+ for (llvm::SmallVectorImpl<SourceRange>::iterator
+ I = Ranges.begin(), E = Ranges.end(); I!=E; ++I)
+ report->addRange(*I);
+
+ C.EmitReport(report);
+ return;
+ }
+ else {
+ // Otherwise, we have the case where the location could either be
+ // null or not-null. Record the error node as an "implicit" null
+ // dereference.
+ if (ExplodedNode *N = C.generateSink(nullState))
+ ImplicitNullDerefNodes.push_back(N);
+ }
+ }
+
+ // From this point forward, we know that the location is not null.
+ C.addTransition(notNullState);
+}
--
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