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llvm-project/clang/AST/Expr.cpp

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//===--- Expr.cpp - Expression AST Node Implementation --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Chris Lattner and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the Expr class and subclasses.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/Expr.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Lex/IdentifierTable.h"
using namespace clang;
//===----------------------------------------------------------------------===//
// Primary Expressions.
//===----------------------------------------------------------------------===//
StringLiteral::StringLiteral(const char *strData, unsigned byteLength,
bool Wide, QualType t, SourceLocation firstLoc,
SourceLocation lastLoc) :
Expr(StringLiteralClass, t) {
// OPTIMIZE: could allocate this appended to the StringLiteral.
char *AStrData = new char[byteLength];
memcpy(AStrData, strData, byteLength);
StrData = AStrData;
ByteLength = byteLength;
IsWide = Wide;
firstTokLoc = firstLoc;
lastTokLoc = lastLoc;
}
StringLiteral::~StringLiteral() {
delete[] StrData;
}
bool UnaryOperator::isPostfix(Opcode Op) {
switch (Op) {
case PostInc:
case PostDec:
return true;
default:
return false;
}
}
/// getOpcodeStr - Turn an Opcode enum value into the punctuation char it
/// corresponds to, e.g. "sizeof" or "[pre]++".
const char *UnaryOperator::getOpcodeStr(Opcode Op) {
switch (Op) {
default: assert(0 && "Unknown unary operator");
case PostInc: return "++";
case PostDec: return "--";
case PreInc: return "++";
case PreDec: return "--";
case AddrOf: return "&";
case Deref: return "*";
case Plus: return "+";
case Minus: return "-";
case Not: return "~";
case LNot: return "!";
case Real: return "__real";
case Imag: return "__imag";
case SizeOf: return "sizeof";
case AlignOf: return "alignof";
case Extension: return "__extension__";
}
}
//===----------------------------------------------------------------------===//
// Postfix Operators.
//===----------------------------------------------------------------------===//
CallExpr::CallExpr(Expr *fn, Expr **args, unsigned numargs, QualType t,
SourceLocation rparenloc)
: Expr(CallExprClass, t), Fn(fn), NumArgs(numargs) {
Args = new Expr*[numargs];
for (unsigned i = 0; i != numargs; ++i)
Args[i] = args[i];
RParenLoc = rparenloc;
}
/// getOpcodeStr - Turn an Opcode enum value into the punctuation char it
/// corresponds to, e.g. "<<=".
const char *BinaryOperator::getOpcodeStr(Opcode Op) {
switch (Op) {
default: assert(0 && "Unknown binary operator");
case Mul: return "*";
case Div: return "/";
case Rem: return "%";
case Add: return "+";
case Sub: return "-";
case Shl: return "<<";
case Shr: return ">>";
case LT: return "<";
case GT: return ">";
case LE: return "<=";
case GE: return ">=";
case EQ: return "==";
case NE: return "!=";
case And: return "&";
case Xor: return "^";
case Or: return "|";
case LAnd: return "&&";
case LOr: return "||";
case Assign: return "=";
case MulAssign: return "*=";
case DivAssign: return "/=";
case RemAssign: return "%=";
case AddAssign: return "+=";
case SubAssign: return "-=";
case ShlAssign: return "<<=";
case ShrAssign: return ">>=";
case AndAssign: return "&=";
case XorAssign: return "^=";
case OrAssign: return "|=";
case Comma: return ",";
}
}
//===----------------------------------------------------------------------===//
// Generic Expression Routines
//===----------------------------------------------------------------------===//
/// hasLocalSideEffect - Return true if this immediate expression has side
/// effects, not counting any sub-expressions.
bool Expr::hasLocalSideEffect() const {
switch (getStmtClass()) {
default:
return false;
case ParenExprClass:
return cast<ParenExpr>(this)->getSubExpr()->hasLocalSideEffect();
case UnaryOperatorClass: {
const UnaryOperator *UO = cast<UnaryOperator>(this);
switch (UO->getOpcode()) {
default: return false;
case UnaryOperator::PostInc:
case UnaryOperator::PostDec:
case UnaryOperator::PreInc:
case UnaryOperator::PreDec:
return true; // ++/--
case UnaryOperator::Deref:
// Dereferencing a volatile pointer is a side-effect.
return getType().isVolatileQualified();
case UnaryOperator::Real:
case UnaryOperator::Imag:
// accessing a piece of a volatile complex is a side-effect.
return UO->getSubExpr()->getType().isVolatileQualified();
case UnaryOperator::Extension:
return UO->getSubExpr()->hasLocalSideEffect();
}
}
case BinaryOperatorClass:
return cast<BinaryOperator>(this)->isAssignmentOp();
case MemberExprClass:
case ArraySubscriptExprClass:
// If the base pointer or element is to a volatile pointer/field, accessing
// if is a side effect.
return getType().isVolatileQualified();
case CallExprClass:
// TODO: check attributes for pure/const. "void foo() { strlen("bar"); }"
// should warn.
return true;
case CastExprClass:
// If this is a cast to void, check the operand. Otherwise, the result of
// the cast is unused.
if (getType()->isVoidType())
return cast<CastExpr>(this)->getSubExpr()->hasLocalSideEffect();
return false;
}
}
/// isLvalue - C99 6.3.2.1: an lvalue is an expression with an object type or an
/// incomplete type other than void. Nonarray expressions that can be lvalues:
/// - name, where name must be a variable
/// - e[i]
/// - (e), where e must be an lvalue
/// - e.name, where e must be an lvalue
/// - e->name
/// - *e, the type of e cannot be a function type
/// - string-constant
///
Expr::isLvalueResult Expr::isLvalue() {
// first, check the type (C99 6.3.2.1)
if (isa<FunctionType>(TR.getCanonicalType())) // from isObjectType()
return LV_NotObjectType;
if (TR->isIncompleteType() && TR->isVoidType())
return LV_IncompleteVoidType;
// the type looks fine, now check the expression
switch (getStmtClass()) {
case StringLiteralClass: // C99 6.5.1p4
case ArraySubscriptExprClass: // C99 6.5.3p4 (e1[e2] == (*((e1)+(e2))))
// For vectors, make sure base is an lvalue (i.e. not a function call).
if (cast<ArraySubscriptExpr>(this)->getBase()->getType()->isVectorType())
return cast<ArraySubscriptExpr>(this)->getBase()->isLvalue();
return LV_Valid;
case DeclRefExprClass: // C99 6.5.1p2
if (isa<VarDecl>(cast<DeclRefExpr>(this)->getDecl()))
return LV_Valid;
break;
case MemberExprClass: { // C99 6.5.2.3p4
const MemberExpr *m = cast<MemberExpr>(this);
return m->isArrow() ? LV_Valid : m->getBase()->isLvalue();
}
case UnaryOperatorClass: // C99 6.5.3p4
if (cast<UnaryOperator>(this)->getOpcode() == UnaryOperator::Deref)
return LV_Valid;
break;
case ParenExprClass: // C99 6.5.1p5
return cast<ParenExpr>(this)->getSubExpr()->isLvalue();
default:
break;
}
return LV_InvalidExpression;
}
/// isModifiableLvalue - C99 6.3.2.1: an lvalue that does not have array type,
/// does not have an incomplete type, does not have a const-qualified type, and
/// if it is a structure or union, does not have any member (including,
/// recursively, any member or element of all contained aggregates or unions)
/// with a const-qualified type.
Expr::isModifiableLvalueResult Expr::isModifiableLvalue() {
isLvalueResult lvalResult = isLvalue();
switch (lvalResult) {
case LV_Valid: break;
case LV_NotObjectType: return MLV_NotObjectType;
case LV_IncompleteVoidType: return MLV_IncompleteVoidType;
case LV_InvalidExpression: return MLV_InvalidExpression;
}
if (TR.isConstQualified())
return MLV_ConstQualified;
if (TR->isArrayType())
return MLV_ArrayType;
if (TR->isIncompleteType())
return MLV_IncompleteType;
if (const RecordType *r = dyn_cast<RecordType>(TR.getCanonicalType())) {
if (r->hasConstFields())
return MLV_ConstQualified;
}
return MLV_Valid;
}
/// isIntegerConstantExpr - this recursive routine will test if an expression is
/// an integer constant expression. Note: With the introduction of VLA's in
/// C99 the result of the sizeof operator is no longer always a constant
/// expression. The generalization of the wording to include any subexpression
/// that is not evaluated (C99 6.6p3) means that nonconstant subexpressions
/// can appear as operands to other operators (e.g. &&, ||, ?:). For instance,
/// "0 || f()" can be treated as a constant expression. In C90 this expression,
/// occurring in a context requiring a constant, would have been a constraint
/// violation. FIXME: This routine currently implements C90 semantics.
/// To properly implement C99 semantics this routine will need to evaluate
/// expressions involving operators previously mentioned.
/// FIXME: Pass up a reason why! Invalid operation in i-c-e, division by zero,
/// comma, etc
///
/// FIXME: This should ext-warn on overflow during evaluation! ISO C does not
/// permit this.
bool Expr::isIntegerConstantExpr(llvm::APSInt &Result, SourceLocation *Loc,
bool isEvaluated) const {
switch (getStmtClass()) {
default:
if (Loc) *Loc = getLocStart();
return false;
case ParenExprClass:
return cast<ParenExpr>(this)->getSubExpr()->
isIntegerConstantExpr(Result, Loc, isEvaluated);
case IntegerLiteralClass:
Result = cast<IntegerLiteral>(this)->getValue();
break;
case CharacterLiteralClass:
// FIXME: This doesn't set the right width etc.
Result.zextOrTrunc(32); // FIXME: NOT RIGHT IN GENERAL.
Result = cast<CharacterLiteral>(this)->getValue();
break;
case DeclRefExprClass:
if (const EnumConstantDecl *D =
dyn_cast<EnumConstantDecl>(cast<DeclRefExpr>(this)->getDecl())) {
Result = D->getInitVal();
break;
}
if (Loc) *Loc = getLocStart();
return false;
case UnaryOperatorClass: {
const UnaryOperator *Exp = cast<UnaryOperator>(this);
// Get the operand value. If this is sizeof/alignof, do not evalute the
// operand. This affects C99 6.6p3.
if (Exp->isSizeOfAlignOfOp()) isEvaluated = false;
if (!Exp->getSubExpr()->isIntegerConstantExpr(Result, Loc, isEvaluated))
return false;
switch (Exp->getOpcode()) {
// Address, indirect, pre/post inc/dec, etc are not valid constant exprs.
// See C99 6.6p3.
default:
if (Loc) *Loc = Exp->getOperatorLoc();
return false;
case UnaryOperator::Extension:
return true;
case UnaryOperator::SizeOf:
case UnaryOperator::AlignOf:
// sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
if (!Exp->getSubExpr()->getType()->isConstantSizeType(Loc))
return false;
// FIXME: Evaluate sizeof/alignof.
Result.zextOrTrunc(32); // FIXME: NOT RIGHT IN GENERAL.
Result = 1; // FIXME: Obviously bogus
break;
case UnaryOperator::LNot: {
bool Val = Result != 0;
Result.zextOrTrunc(32); // FIXME: NOT RIGHT IN GENERAL.
Result = Val;
break;
}
case UnaryOperator::Plus:
// FIXME: Do usual unary promotions here!
break;
case UnaryOperator::Minus:
// FIXME: Do usual unary promotions here!
Result = -Result;
break;
case UnaryOperator::Not:
// FIXME: Do usual unary promotions here!
Result = ~Result;
break;
}
break;
}
case SizeOfAlignOfTypeExprClass: {
const SizeOfAlignOfTypeExpr *Exp = cast<SizeOfAlignOfTypeExpr>(this);
// alignof always evaluates to a constant.
if (Exp->isSizeOf() && !Exp->getArgumentType()->isConstantSizeType(Loc))
return false;
// FIXME: Evaluate sizeof/alignof.
Result.zextOrTrunc(32); // FIXME: NOT RIGHT IN GENERAL.
Result = 1; // FIXME: Obviously bogus
break;
}
case BinaryOperatorClass: {
const BinaryOperator *Exp = cast<BinaryOperator>(this);
// The LHS of a constant expr is always evaluated and needed.
if (!Exp->getLHS()->isIntegerConstantExpr(Result, Loc, isEvaluated))
return false;
llvm::APSInt RHS(Result);
// The short-circuiting &&/|| operators don't necessarily evaluate their
// RHS. Make sure to pass isEvaluated down correctly.
if (Exp->isLogicalOp()) {
bool RHSEval;
if (Exp->getOpcode() == BinaryOperator::LAnd)
RHSEval = Result != 0;
else {
assert(Exp->getOpcode() == BinaryOperator::LOr &&"Unexpected logical");
RHSEval = Result == 0;
}
if (!Exp->getRHS()->isIntegerConstantExpr(RHS, Loc,
isEvaluated & RHSEval))
return false;
} else {
if (!Exp->getRHS()->isIntegerConstantExpr(RHS, Loc, isEvaluated))
return false;
}
// FIXME: These should all do the standard promotions, etc.
switch (Exp->getOpcode()) {
default:
if (Loc) *Loc = getLocStart();
return false;
case BinaryOperator::Mul:
Result *= RHS;
break;
case BinaryOperator::Div:
if (RHS == 0) {
if (!isEvaluated) break;
if (Loc) *Loc = getLocStart();
return false;
}
Result /= RHS;
break;
case BinaryOperator::Rem:
if (RHS == 0) {
if (!isEvaluated) break;
if (Loc) *Loc = getLocStart();
return false;
}
Result %= RHS;
break;
case BinaryOperator::Add: Result += RHS; break;
case BinaryOperator::Sub: Result -= RHS; break;
case BinaryOperator::Shl:
Result <<= RHS.getLimitedValue(Result.getBitWidth()-1);
break;
case BinaryOperator::Shr:
Result >>= RHS.getLimitedValue(Result.getBitWidth()-1);
break;
case BinaryOperator::LT: Result = Result < RHS; break;
case BinaryOperator::GT: Result = Result > RHS; break;
case BinaryOperator::LE: Result = Result <= RHS; break;
case BinaryOperator::GE: Result = Result >= RHS; break;
case BinaryOperator::EQ: Result = Result == RHS; break;
case BinaryOperator::NE: Result = Result != RHS; break;
case BinaryOperator::And: Result &= RHS; break;
case BinaryOperator::Xor: Result ^= RHS; break;
case BinaryOperator::Or: Result |= RHS; break;
case BinaryOperator::LAnd:
Result = Result != 0 && RHS != 0;
break;
case BinaryOperator::LOr:
Result = Result != 0 || RHS != 0;
break;
case BinaryOperator::Comma:
// C99 6.6p3: "shall not contain assignment, ..., or comma operators,
// *except* when they are contained within a subexpression that is not
// evaluated". Note that Assignment can never happen due to constraints
// on the LHS subexpr, so we don't need to check it here.
if (isEvaluated) {
if (Loc) *Loc = getLocStart();
return false;
}
// The result of the constant expr is the RHS.
Result = RHS;
return true;
}
assert(!Exp->isAssignmentOp() && "LHS can't be a constant expr!");
break;
}
case CastExprClass: {
const CastExpr *Exp = cast<CastExpr>(this);
// C99 6.6p6: shall only convert arithmetic types to integer types.
if (!Exp->getSubExpr()->getType()->isArithmeticType() ||
!Exp->getDestType()->isIntegerType()) {
if (Loc) *Loc = Exp->getSubExpr()->getLocStart();
return false;
}
// Handle simple integer->integer casts.
if (Exp->getSubExpr()->getType()->isIntegerType()) {
if (!Exp->getSubExpr()->isIntegerConstantExpr(Result, Loc, isEvaluated))
return false;
// FIXME: do the conversion on Result.
break;
}
// Allow floating constants that are the immediate operands of casts or that
// are parenthesized.
const Expr *Operand = Exp->getSubExpr();
while (const ParenExpr *PE = dyn_cast<ParenExpr>(Operand))
Operand = PE->getSubExpr();
if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(Operand)) {
// FIXME: Evaluate this correctly!
Result = (int)FL->getValue();
break;
}
if (Loc) *Loc = Operand->getLocStart();
return false;
}
case ConditionalOperatorClass: {
const ConditionalOperator *Exp = cast<ConditionalOperator>(this);
if (!Exp->getCond()->isIntegerConstantExpr(Result, Loc, isEvaluated))
return false;
const Expr *TrueExp = Exp->getLHS();
const Expr *FalseExp = Exp->getRHS();
if (Result == 0) std::swap(TrueExp, FalseExp);
// Evaluate the false one first, discard the result.
if (!FalseExp->isIntegerConstantExpr(Result, Loc, false))
return false;
// Evalute the true one, capture the result.
if (!TrueExp->isIntegerConstantExpr(Result, Loc, isEvaluated))
return false;
// FIXME: promotions on result.
break;
}
}
// Cases that are valid constant exprs fall through to here.
Result.setIsUnsigned(getType()->isUnsignedIntegerType());
return true;
}
/// isNullPointerConstant - C99 6.3.2.3p3 - Return true if this is either an
/// integer constant expression with the value zero, or if this is one that is
/// cast to void*.
bool Expr::isNullPointerConstant() const {
// Strip off a cast to void*, if it exists.
if (const CastExpr *CE = dyn_cast<CastExpr>(this)) {
// Check that it is a cast to void*.
if (const PointerType *PT = dyn_cast<PointerType>(CE->getType())) {
QualType Pointee = PT->getPointeeType();
if (Pointee.getQualifiers() == 0 && Pointee->isVoidType() && // to void*
CE->getSubExpr()->getType()->isIntegerType()) // from int.
return CE->getSubExpr()->isNullPointerConstant();
}
} else if (const ParenExpr *PE = dyn_cast<ParenExpr>(this)) {
// Accept ((void*)0) as a null pointer constant, as many other
// implementations do.
return PE->getSubExpr()->isNullPointerConstant();
}
// This expression must be an integer type.
if (!getType()->isIntegerType())
return false;
// If we have an integer constant expression, we need to *evaluate* it and
// test for the value 0.
llvm::APSInt Val(32);
return isIntegerConstantExpr(Val, 0, true) && Val == 0;
}
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