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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 "GRExprEngineInternalChecks.h"
#include "clang/Checker/PathSensitive/Checker.h"
using namespace clang;
namespace {
class UndefBranchChecker : public Checker {
BuiltinBug *BT;
struct FindUndefExpr {
GRStateManager& VM;
const GRState* St;
FindUndefExpr(GRStateManager& V, const GRState* S) : VM(V), St(S) {}
Expr* FindExpr(Expr* Ex) {
if (!MatchesCriteria(Ex))
return 0;
for (Stmt::child_iterator I=Ex->child_begin(), E=Ex->child_end();I!=E;++I)
if (Expr* ExI = dyn_cast_or_null<Expr>(*I)) {
Expr* E2 = FindExpr(ExI);
if (E2) return E2;
return Ex;
bool MatchesCriteria(Expr* Ex) { return St->getSVal(Ex).isUndef(); }
UndefBranchChecker() : BT(0) {}
static void *getTag();
void VisitBranchCondition(GRBranchNodeBuilder &Builder, GRExprEngine &Eng,
Stmt *Condition, void *tag);
void clang::RegisterUndefBranchChecker(GRExprEngine &Eng) {
Eng.registerCheck(new UndefBranchChecker());
void *UndefBranchChecker::getTag() {
static int x;
return &x;
void UndefBranchChecker::VisitBranchCondition(GRBranchNodeBuilder &Builder,
GRExprEngine &Eng,
Stmt *Condition, void *tag) {
const GRState *state = Builder.getState();
SVal X = state->getSVal(Condition);
if (X.isUndef()) {
ExplodedNode *N = Builder.generateNode(state, true);
if (N) {
if (!BT)
BT = 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.
BlockEdge B = cast<BlockEdge>(N->getLocation());
Expr* Ex = cast<Expr>(B.getSrc()->getTerminatorCondition());
assert (Ex && "Block must have a terminator.");
// 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.
assert (!N->pred_empty());
// 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.
ExplodedNode *PrevN = *N->pred_begin();
ProgramPoint P = PrevN->getLocation();
const GRState* St = N->getState();
if (PostStmt* PS = dyn_cast<PostStmt>(&P))
if (PS->getStmt() == Ex)
St = PrevN->getState();
FindUndefExpr FindIt(Eng.getStateManager(), St);
Ex = FindIt.FindExpr(Ex);
// Emit the bug report.
EnhancedBugReport *R = new EnhancedBugReport(*BT, BT->getDescription(),N);
R->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, Ex);