//== ReturnStackAddressChecker.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 ReturnStackAddressChecker, which is a path-sensitive
// check which looks for the addresses of stack variables being returned to
// callers.
//
//===----------------------------------------------------------------------===//

#include "GRExprEngineInternalChecks.h"
#include "clang/Checker/PathSensitive/GRExprEngine.h"
#include "clang/Checker/BugReporter/BugReporter.h"
#include "clang/Checker/PathSensitive/CheckerVisitor.h"
#include "clang/Basic/SourceManager.h"
#include "llvm/ADT/SmallString.h"

using namespace clang;

namespace {
class ReturnStackAddressChecker : 
    public CheckerVisitor<ReturnStackAddressChecker> {      
  BuiltinBug *BT;
public:
  ReturnStackAddressChecker() : BT(0) {}
  static void *getTag();
  void PreVisitReturnStmt(CheckerContext &C, const ReturnStmt *RS);
private:
  void EmitStackError(CheckerContext &C, const MemRegion *R, const Expr *RetE);
};
}

void clang::RegisterReturnStackAddressChecker(GRExprEngine &Eng) {
  Eng.registerCheck(new ReturnStackAddressChecker());
}

void *ReturnStackAddressChecker::getTag() {
  static int x = 0; return &x;
}

void ReturnStackAddressChecker::EmitStackError(CheckerContext &C,
                                               const MemRegion *R,
                                               const Expr *RetE) {
	ExplodedNode *N = C.GenerateSink();

	if (!N)
		return;

	if (!BT)
		BT = new BuiltinBug("Return of address to stack-allocated memory");

	// Generate a report for this bug.
	llvm::SmallString<512> buf;
	llvm::raw_svector_ostream os(buf);
	SourceRange range;

	// Get the base region, stripping away fields and elements.
	R = R->getBaseRegion();

	// Check if the region is a compound literal.
	if (const CompoundLiteralRegion* CR = dyn_cast<CompoundLiteralRegion>(R)) {    
		const CompoundLiteralExpr* CL = CR->getLiteralExpr();
		os << "Address of stack memory associated with a compound literal "
          "declared on line "
       << C.getSourceManager().getInstantiationLineNumber(CL->getLocStart())
       << " returned to caller";    
		range = CL->getSourceRange();
	}
	else if (const AllocaRegion* AR = dyn_cast<AllocaRegion>(R)) {
		const Expr* ARE = AR->getExpr();
		SourceLocation L = ARE->getLocStart();
		range = ARE->getSourceRange();    
		os << "Address of stack memory allocated by call to alloca() on line "
       << C.getSourceManager().getInstantiationLineNumber(L)
       << " returned to caller";
	}
	else if (const BlockDataRegion *BR = dyn_cast<BlockDataRegion>(R)) {
		const BlockDecl *BD = BR->getCodeRegion()->getDecl();
		SourceLocation L = BD->getLocStart();
		range = BD->getSourceRange();
		os << "Address of stack-allocated block declared on line "
       << C.getSourceManager().getInstantiationLineNumber(L)
       << " returned to caller";
	}
	else if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
		os << "Address of stack memory associated with local variable '"
       << VR->getString() << "' returned";
		range = VR->getDecl()->getSourceRange();
	}
	else {
		assert(false && "Invalid region in ReturnStackAddressChecker.");
		return;
	}

	RangedBugReport *report = new RangedBugReport(*BT, os.str(), N);
	report->addRange(RetE->getSourceRange());
	if (range.isValid())
		report->addRange(range);

	C.EmitReport(report);
}	

void ReturnStackAddressChecker::PreVisitReturnStmt(CheckerContext &C,
                                                   const ReturnStmt *RS) {
  
  const Expr *RetE = RS->getRetValue();
  if (!RetE)
    return;
 
  SVal V = C.getState()->getSVal(RetE);
  const MemRegion *R = V.getAsRegion();

  if (!R || !R->hasStackStorage())
    return;  
  
  if (R->hasStackStorage()) {
    EmitStackError(C, R, RetE);
    return;
  }
}