112 lines
3.7 KiB
C++
112 lines
3.7 KiB
C++
//=== UndefBranchChecker.cpp -----------------------------------*- C++ -*--===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines UndefBranchChecker, which checks for undefined branch
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// condition.
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//
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//===----------------------------------------------------------------------===//
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#include "ClangSACheckers.h"
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#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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using namespace clang;
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using namespace ento;
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namespace {
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class UndefBranchChecker : public Checker<check::BranchCondition> {
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mutable OwningPtr<BuiltinBug> BT;
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struct FindUndefExpr {
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ProgramStateRef St;
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const LocationContext *LCtx;
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FindUndefExpr(ProgramStateRef S, const LocationContext *L)
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: St(S), LCtx(L) {}
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const Expr *FindExpr(const Expr *Ex) {
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if (!MatchesCriteria(Ex))
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return 0;
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for (Stmt::const_child_iterator I = Ex->child_begin(),
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E = Ex->child_end();I!=E;++I)
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if (const Expr *ExI = dyn_cast_or_null<Expr>(*I)) {
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const Expr *E2 = FindExpr(ExI);
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if (E2) return E2;
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}
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return Ex;
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}
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bool MatchesCriteria(const Expr *Ex) {
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return St->getSVal(Ex, LCtx).isUndef();
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}
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};
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public:
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void checkBranchCondition(const Stmt *Condition, CheckerContext &Ctx) const;
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};
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}
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void UndefBranchChecker::checkBranchCondition(const Stmt *Condition,
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CheckerContext &Ctx) const {
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SVal X = Ctx.getState()->getSVal(Condition, Ctx.getLocationContext());
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if (X.isUndef()) {
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// Generate a sink node, which implicitly marks both outgoing branches as
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// infeasible.
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ExplodedNode *N = Ctx.generateSink();
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if (N) {
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if (!BT)
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BT.reset(
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new BuiltinBug("Branch condition evaluates to a garbage value"));
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// What's going on here: we want to highlight the subexpression of the
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// condition that is the most likely source of the "uninitialized
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// branch condition." We do a recursive walk of the condition's
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// subexpressions and roughly look for the most nested subexpression
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// that binds to Undefined. We then highlight that expression's range.
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// Get the predecessor node and check if is a PostStmt with the Stmt
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// being the terminator condition. We want to inspect the state
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// of that node instead because it will contain main information about
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// the subexpressions.
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// Note: any predecessor will do. They should have identical state,
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// since all the BlockEdge did was act as an error sink since the value
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// had to already be undefined.
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assert (!N->pred_empty());
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const Expr *Ex = cast<Expr>(Condition);
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ExplodedNode *PrevN = *N->pred_begin();
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ProgramPoint P = PrevN->getLocation();
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ProgramStateRef St = N->getState();
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if (Optional<PostStmt> PS = P.getAs<PostStmt>())
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if (PS->getStmt() == Ex)
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St = PrevN->getState();
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FindUndefExpr FindIt(St, Ctx.getLocationContext());
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Ex = FindIt.FindExpr(Ex);
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// Emit the bug report.
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BugReport *R = new BugReport(*BT, BT->getDescription(), N);
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bugreporter::trackNullOrUndefValue(N, Ex, *R);
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R->addRange(Ex->getSourceRange());
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Ctx.emitReport(R);
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}
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}
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}
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void ento::registerUndefBranchChecker(CheckerManager &mgr) {
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mgr.registerChecker<UndefBranchChecker>();
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}
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