// SValBuilder.cpp - Basic class for all SValBuilder implementations -*- 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 SValBuilder, the base class for all (complete) SValBuilder
// implementations.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/ExprCXX.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
using namespace clang;
using namespace ento;
//===----------------------------------------------------------------------===//
// Basic SVal creation.
//===----------------------------------------------------------------------===//
void SValBuilder::anchor() { }
DefinedOrUnknownSVal SValBuilder::makeZeroVal(QualType type) {
if (Loc::isLocType(type))
return makeNull();
if (type->isIntegralOrEnumerationType())
return makeIntVal(0, type);
// FIXME: Handle floats.
// FIXME: Handle structs.
return UnknownVal();
}
NonLoc SValBuilder::makeNonLoc(const SymExpr *lhs, BinaryOperator::Opcode op,
const llvm::APSInt& rhs, QualType type) {
// The Environment ensures we always get a persistent APSInt in
// BasicValueFactory, so we don't need to get the APSInt from
// BasicValueFactory again.
assert(lhs);
assert(!Loc::isLocType(type));
return nonloc::SymbolVal(SymMgr.getSymIntExpr(lhs, op, rhs, type));
}
NonLoc SValBuilder::makeNonLoc(const llvm::APSInt& lhs,
BinaryOperator::Opcode op, const SymExpr *rhs,
QualType type) {
assert(rhs);
assert(!Loc::isLocType(type));
return nonloc::SymbolVal(SymMgr.getIntSymExpr(lhs, op, rhs, type));
}
NonLoc SValBuilder::makeNonLoc(const SymExpr *lhs, BinaryOperator::Opcode op,
const SymExpr *rhs, QualType type) {
assert(lhs && rhs);
assert(!Loc::isLocType(type));
return nonloc::SymbolVal(SymMgr.getSymSymExpr(lhs, op, rhs, type));
}
NonLoc SValBuilder::makeNonLoc(const SymExpr *operand,
QualType fromTy, QualType toTy) {
assert(operand);
assert(!Loc::isLocType(toTy));
return nonloc::SymbolVal(SymMgr.getCastSymbol(operand, fromTy, toTy));
}
SVal SValBuilder::convertToArrayIndex(SVal val) {
if (val.isUnknownOrUndef())
return val;
// Common case: we have an appropriately sized integer.
if (Optional<nonloc::ConcreteInt> CI = val.getAs<nonloc::ConcreteInt>()) {
const llvm::APSInt& I = CI->getValue();
if (I.getBitWidth() == ArrayIndexWidth && I.isSigned())
return val;
}
return evalCastFromNonLoc(val.castAs<NonLoc>(), ArrayIndexTy);
}
nonloc::ConcreteInt SValBuilder::makeBoolVal(const CXXBoolLiteralExpr *boolean){
return makeTruthVal(boolean->getValue());
}
DefinedOrUnknownSVal
SValBuilder::getRegionValueSymbolVal(const TypedValueRegion* region) {
QualType T = region->getValueType();
if (!SymbolManager::canSymbolicate(T))
return UnknownVal();
SymbolRef sym = SymMgr.getRegionValueSymbol(region);
if (Loc::isLocType(T))
return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
return nonloc::SymbolVal(sym);
}
DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *SymbolTag,
const Expr *Ex,
const LocationContext *LCtx,
unsigned Count) {
QualType T = Ex->getType();
// Compute the type of the result. If the expression is not an R-value, the
// result should be a location.
QualType ExType = Ex->getType();
if (Ex->isGLValue())
T = LCtx->getAnalysisDeclContext()->getASTContext().getPointerType(ExType);
return conjureSymbolVal(SymbolTag, Ex, LCtx, T, Count);
}
DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *symbolTag,
const Expr *expr,
const LocationContext *LCtx,
QualType type,
unsigned count) {
if (!SymbolManager::canSymbolicate(type))
return UnknownVal();
SymbolRef sym = SymMgr.conjureSymbol(expr, LCtx, type, count, symbolTag);
if (Loc::isLocType(type))
return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
return nonloc::SymbolVal(sym);
}
DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const Stmt *stmt,
const LocationContext *LCtx,
QualType type,
unsigned visitCount) {
if (!SymbolManager::canSymbolicate(type))
return UnknownVal();
SymbolRef sym = SymMgr.conjureSymbol(stmt, LCtx, type, visitCount);
if (Loc::isLocType(type))
return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
return nonloc::SymbolVal(sym);
}
DefinedOrUnknownSVal
SValBuilder::getConjuredHeapSymbolVal(const Expr *E,
const LocationContext *LCtx,
unsigned VisitCount) {
QualType T = E->getType();
assert(Loc::isLocType(T));
assert(SymbolManager::canSymbolicate(T));
SymbolRef sym = SymMgr.conjureSymbol(E, LCtx, T, VisitCount);
return loc::MemRegionVal(MemMgr.getSymbolicHeapRegion(sym));
}
DefinedSVal SValBuilder::getMetadataSymbolVal(const void *symbolTag,
const MemRegion *region,
const Expr *expr, QualType type,
unsigned count) {
assert(SymbolManager::canSymbolicate(type) && "Invalid metadata symbol type");
SymbolRef sym =
SymMgr.getMetadataSymbol(region, expr, type, count, symbolTag);
if (Loc::isLocType(type))
return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
return nonloc::SymbolVal(sym);
}
DefinedOrUnknownSVal
SValBuilder::getDerivedRegionValueSymbolVal(SymbolRef parentSymbol,
const TypedValueRegion *region) {
QualType T = region->getValueType();
if (!SymbolManager::canSymbolicate(T))
return UnknownVal();
SymbolRef sym = SymMgr.getDerivedSymbol(parentSymbol, region);
if (Loc::isLocType(T))
return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
return nonloc::SymbolVal(sym);
}
DefinedSVal SValBuilder::getFunctionPointer(const FunctionDecl *func) {
return loc::MemRegionVal(MemMgr.getFunctionTextRegion(func));
}
DefinedSVal SValBuilder::getBlockPointer(const BlockDecl *block,
CanQualType locTy,
const LocationContext *locContext,
unsigned blockCount) {
const BlockTextRegion *BC =
MemMgr.getBlockTextRegion(block, locTy, locContext->getAnalysisDeclContext());
const BlockDataRegion *BD = MemMgr.getBlockDataRegion(BC, locContext,
blockCount);
return loc::MemRegionVal(BD);
}
/// Return a memory region for the 'this' object reference.
loc::MemRegionVal SValBuilder::getCXXThis(const CXXMethodDecl *D,
const StackFrameContext *SFC) {
return loc::MemRegionVal(getRegionManager().
getCXXThisRegion(D->getThisType(getContext()), SFC));
}
/// Return a memory region for the 'this' object reference.
loc::MemRegionVal SValBuilder::getCXXThis(const CXXRecordDecl *D,
const StackFrameContext *SFC) {
const Type *T = D->getTypeForDecl();
QualType PT = getContext().getPointerType(QualType(T, 0));
return loc::MemRegionVal(getRegionManager().getCXXThisRegion(PT, SFC));
}
Optional<SVal> SValBuilder::getConstantVal(const Expr *E) {
E = E->IgnoreParens();
switch (E->getStmtClass()) {
// Handle expressions that we treat differently from the AST's constant
// evaluator.
case Stmt::AddrLabelExprClass:
return makeLoc(cast<AddrLabelExpr>(E));
case Stmt::CXXScalarValueInitExprClass:
case Stmt::ImplicitValueInitExprClass:
return makeZeroVal(E->getType());
case Stmt::ObjCStringLiteralClass: {
const ObjCStringLiteral *SL = cast<ObjCStringLiteral>(E);
return makeLoc(getRegionManager().getObjCStringRegion(SL));
}
case Stmt::StringLiteralClass: {
const StringLiteral *SL = cast<StringLiteral>(E);
return makeLoc(getRegionManager().getStringRegion(SL));
}
// Fast-path some expressions to avoid the overhead of going through the AST's
// constant evaluator
case Stmt::CharacterLiteralClass: {
const CharacterLiteral *C = cast<CharacterLiteral>(E);
return makeIntVal(C->getValue(), C->getType());
}
case Stmt::CXXBoolLiteralExprClass:
return makeBoolVal(cast<CXXBoolLiteralExpr>(E));
case Stmt::IntegerLiteralClass:
return makeIntVal(cast<IntegerLiteral>(E));
case Stmt::ObjCBoolLiteralExprClass:
return makeBoolVal(cast<ObjCBoolLiteralExpr>(E));
case Stmt::CXXNullPtrLiteralExprClass:
return makeNull();
case Stmt::ImplicitCastExprClass: {
const CastExpr *CE = cast<CastExpr>(E);
if (CE->getCastKind() == CK_ArrayToPointerDecay) {
Optional<SVal> ArrayVal = getConstantVal(CE->getSubExpr());
if (!ArrayVal)
return None;
return evalCast(*ArrayVal, CE->getType(), CE->getSubExpr()->getType());
}
// FALLTHROUGH
}
// If we don't have a special case, fall back to the AST's constant evaluator.
default: {
// Don't try to come up with a value for materialized temporaries.
if (E->isGLValue())
return None;
ASTContext &Ctx = getContext();
llvm::APSInt Result;
if (E->EvaluateAsInt(Result, Ctx))
return makeIntVal(Result);
if (Loc::isLocType(E->getType()))
if (E->isNullPointerConstant(Ctx, Expr::NPC_ValueDependentIsNotNull))
return makeNull();
return None;
}
}
}
//===----------------------------------------------------------------------===//
SVal SValBuilder::makeSymExprValNN(ProgramStateRef State,
BinaryOperator::Opcode Op,
NonLoc LHS, NonLoc RHS,
QualType ResultTy) {
if (!State->isTainted(RHS) && !State->isTainted(LHS))
return UnknownVal();
const SymExpr *symLHS = LHS.getAsSymExpr();
const SymExpr *symRHS = RHS.getAsSymExpr();
// TODO: When the Max Complexity is reached, we should conjure a symbol
// instead of generating an Unknown value and propagate the taint info to it.
const unsigned MaxComp = 10000; // 100000 28X
if (symLHS && symRHS &&
(symLHS->computeComplexity() + symRHS->computeComplexity()) < MaxComp)
return makeNonLoc(symLHS, Op, symRHS, ResultTy);
if (symLHS && symLHS->computeComplexity() < MaxComp)
if (Optional<nonloc::ConcreteInt> rInt = RHS.getAs<nonloc::ConcreteInt>())
return makeNonLoc(symLHS, Op, rInt->getValue(), ResultTy);
if (symRHS && symRHS->computeComplexity() < MaxComp)
if (Optional<nonloc::ConcreteInt> lInt = LHS.getAs<nonloc::ConcreteInt>())
return makeNonLoc(lInt->getValue(), Op, symRHS, ResultTy);
return UnknownVal();
}
SVal SValBuilder::evalBinOp(ProgramStateRef state, BinaryOperator::Opcode op,
SVal lhs, SVal rhs, QualType type) {
if (lhs.isUndef() || rhs.isUndef())
return UndefinedVal();
if (lhs.isUnknown() || rhs.isUnknown())
return UnknownVal();
if (Optional<Loc> LV = lhs.getAs<Loc>()) {
if (Optional<Loc> RV = rhs.getAs<Loc>())
return evalBinOpLL(state, op, *LV, *RV, type);
return evalBinOpLN(state, op, *LV, rhs.castAs<NonLoc>(), type);
}
if (Optional<Loc> RV = rhs.getAs<Loc>()) {
// Support pointer arithmetic where the addend is on the left
// and the pointer on the right.
assert(op == BO_Add);
// Commute the operands.
return evalBinOpLN(state, op, *RV, lhs.castAs<NonLoc>(), type);
}
return evalBinOpNN(state, op, lhs.castAs<NonLoc>(), rhs.castAs<NonLoc>(),
type);
}
DefinedOrUnknownSVal SValBuilder::evalEQ(ProgramStateRef state,
DefinedOrUnknownSVal lhs,
DefinedOrUnknownSVal rhs) {
return evalBinOp(state, BO_EQ, lhs, rhs, getConditionType())
.castAs<DefinedOrUnknownSVal>();
}
/// Recursively check if the pointer types are equal modulo const, volatile,
/// and restrict qualifiers. Also, assume that all types are similar to 'void'.
/// Assumes the input types are canonical.
static bool shouldBeModeledWithNoOp(ASTContext &Context, QualType ToTy,
QualType FromTy) {
while (Context.UnwrapSimilarPointerTypes(ToTy, FromTy)) {
Qualifiers Quals1, Quals2;
ToTy = Context.getUnqualifiedArrayType(ToTy, Quals1);
FromTy = Context.getUnqualifiedArrayType(FromTy, Quals2);
// Make sure that non-cvr-qualifiers the other qualifiers (e.g., address
// spaces) are identical.
Quals1.removeCVRQualifiers();
Quals2.removeCVRQualifiers();
if (Quals1 != Quals2)
return false;
}
// If we are casting to void, the 'From' value can be used to represent the
// 'To' value.
if (ToTy->isVoidType())
return true;
if (ToTy != FromTy)
return false;
return true;
}
// FIXME: should rewrite according to the cast kind.
SVal SValBuilder::evalCast(SVal val, QualType castTy, QualType originalTy) {
castTy = Context.getCanonicalType(castTy);
originalTy = Context.getCanonicalType(originalTy);
if (val.isUnknownOrUndef() || castTy == originalTy)
return val;
if (castTy->isBooleanType()) {
if (val.isUnknownOrUndef())
return val;
if (val.isConstant())
return makeTruthVal(!val.isZeroConstant(), castTy);
if (!Loc::isLocType(originalTy) &&
!originalTy->isIntegralOrEnumerationType() &&
!originalTy->isMemberPointerType())
return UnknownVal();
if (SymbolRef Sym = val.getAsSymbol(true)) {
BasicValueFactory &BVF = getBasicValueFactory();
// FIXME: If we had a state here, we could see if the symbol is known to
// be zero, but we don't.
return makeNonLoc(Sym, BO_NE, BVF.getValue(0, Sym->getType()), castTy);
}
// Loc values are not always true, they could be weakly linked functions.
if (Optional<Loc> L = val.getAs<Loc>())
return evalCastFromLoc(*L, castTy);
Loc L = val.castAs<nonloc::LocAsInteger>().getLoc();
return evalCastFromLoc(L, castTy);
}
// For const casts, casts to void, just propagate the value.
if (!castTy->isVariableArrayType() && !originalTy->isVariableArrayType())
if (shouldBeModeledWithNoOp(Context, Context.getPointerType(castTy),
Context.getPointerType(originalTy)))
return val;
// Check for casts from pointers to integers.
if (castTy->isIntegralOrEnumerationType() && Loc::isLocType(originalTy))
return evalCastFromLoc(val.castAs<Loc>(), castTy);
// Check for casts from integers to pointers.
if (Loc::isLocType(castTy) && originalTy->isIntegralOrEnumerationType()) {
if (Optional<nonloc::LocAsInteger> LV = val.getAs<nonloc::LocAsInteger>()) {
if (const MemRegion *R = LV->getLoc().getAsRegion()) {
StoreManager &storeMgr = StateMgr.getStoreManager();
R = storeMgr.castRegion(R, castTy);
return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
}
return LV->getLoc();
}
return dispatchCast(val, castTy);
}
// Just pass through function and block pointers.
if (originalTy->isBlockPointerType() || originalTy->isFunctionPointerType()) {
assert(Loc::isLocType(castTy));
return val;
}
// Check for casts from array type to another type.
if (const ArrayType *arrayT =
dyn_cast<ArrayType>(originalTy.getCanonicalType())) {
// We will always decay to a pointer.
QualType elemTy = arrayT->getElementType();
val = StateMgr.ArrayToPointer(val.castAs<Loc>(), elemTy);
// Are we casting from an array to a pointer? If so just pass on
// the decayed value.
if (castTy->isPointerType() || castTy->isReferenceType())
return val;
// Are we casting from an array to an integer? If so, cast the decayed
// pointer value to an integer.
assert(castTy->isIntegralOrEnumerationType());
// FIXME: Keep these here for now in case we decide soon that we
// need the original decayed type.
// QualType elemTy = cast<ArrayType>(originalTy)->getElementType();
// QualType pointerTy = C.getPointerType(elemTy);
return evalCastFromLoc(val.castAs<Loc>(), castTy);
}
// Check for casts from a region to a specific type.
if (const MemRegion *R = val.getAsRegion()) {
// Handle other casts of locations to integers.
if (castTy->isIntegralOrEnumerationType())
return evalCastFromLoc(loc::MemRegionVal(R), castTy);
// FIXME: We should handle the case where we strip off view layers to get
// to a desugared type.
if (!Loc::isLocType(castTy)) {
// FIXME: There can be gross cases where one casts the result of a function
// (that returns a pointer) to some other value that happens to fit
// within that pointer value. We currently have no good way to
// model such operations. When this happens, the underlying operation
// is that the caller is reasoning about bits. Conceptually we are
// layering a "view" of a location on top of those bits. Perhaps
// we need to be more lazy about mutual possible views, even on an
// SVal? This may be necessary for bit-level reasoning as well.
return UnknownVal();
}
// We get a symbolic function pointer for a dereference of a function
// pointer, but it is of function type. Example:
// struct FPRec {
// void (*my_func)(int * x);
// };
//
// int bar(int x);
//
// int f1_a(struct FPRec* foo) {
// int x;
// (*foo->my_func)(&x);
// return bar(x)+1; // no-warning
// }
assert(Loc::isLocType(originalTy) || originalTy->isFunctionType() ||
originalTy->isBlockPointerType() || castTy->isReferenceType());
StoreManager &storeMgr = StateMgr.getStoreManager();
// Delegate to store manager to get the result of casting a region to a
// different type. If the MemRegion* returned is NULL, this expression
// Evaluates to UnknownVal.
R = storeMgr.castRegion(R, castTy);
return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
}
return dispatchCast(val, castTy);
}