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