Example #1
0
File: stmt.go Project: tcard/sgo
// goVal returns the Go value for val, or nil.
func goVal(val constant.Value) interface{} {
	// val should exist, but be conservative and check
	if val == nil {
		return nil
	}
	// Match implementation restriction of other compilers.
	// gc only checks duplicates for integer, floating-point
	// and string values, so only create Go values for these
	// types.
	switch val.Kind() {
	case constant.Int:
		if x, ok := constant.Int64Val(val); ok {
			return x
		}
		if x, ok := constant.Uint64Val(val); ok {
			return x
		}
	case constant.Float:
		if x, ok := constant.Float64Val(val); ok {
			return x
		}
	case constant.String:
		return constant.StringVal(val)
	}
	return nil
}
Example #2
0
File: expr.go Project: tcard/sgo
func (check *Checker) shift(x, y *operand, e *ast.BinaryExpr, op token.Token) {
	untypedx := isUntyped(x.typ)

	var xval constant.Value
	if x.mode == constant_ {
		xval = constant.ToInt(x.val)
	}

	if isInteger(x.typ) || untypedx && xval != nil && xval.Kind() == constant.Int {
		// The lhs is of integer type or an untyped constant representable
		// as an integer. Nothing to do.
	} else {
		// shift has no chance
		check.invalidOp(x.pos(), "shifted operand %s must be integer", x)
		x.mode = invalid
		return
	}

	// spec: "The right operand in a shift expression must have unsigned
	// integer type or be an untyped constant that can be converted to
	// unsigned integer type."
	switch {
	case isUnsigned(y.typ):
		// nothing to do
	case isUntyped(y.typ):
		check.convertUntyped(y, Typ[UntypedInt])
		if y.mode == invalid {
			x.mode = invalid
			return
		}
	default:
		check.invalidOp(y.pos(), "shift count %s must be unsigned integer", y)
		x.mode = invalid
		return
	}

	if x.mode == constant_ {
		if y.mode == constant_ {
			// rhs must be an integer value
			yval := constant.ToInt(y.val)
			if yval.Kind() != constant.Int {
				check.invalidOp(y.pos(), "shift count %s must be unsigned integer", y)
				x.mode = invalid
				return
			}
			// rhs must be within reasonable bounds
			const shiftBound = 1023 - 1 + 52 // so we can express smallestFloat64
			s, ok := constant.Uint64Val(yval)
			if !ok || s > shiftBound {
				check.invalidOp(y.pos(), "invalid shift count %s", y)
				x.mode = invalid
				return
			}
			// The lhs is representable as an integer but may not be an integer
			// (e.g., 2.0, an untyped float) - this can only happen for untyped
			// non-integer numeric constants. Correct the type so that the shift
			// result is of integer type.
			if !isInteger(x.typ) {
				x.typ = Typ[UntypedInt]
			}
			// x is a constant so xval != nil and it must be of Int kind.
			x.val = constant.Shift(xval, op, uint(s))
			// Typed constants must be representable in
			// their type after each constant operation.
			if isTyped(x.typ) {
				if e != nil {
					x.expr = e // for better error message
				}
				check.representable(x, x.typ.Underlying().(*Basic))
			}
			return
		}

		// non-constant shift with constant lhs
		if untypedx {
			// spec: "If the left operand of a non-constant shift
			// expression is an untyped constant, the type of the
			// constant is what it would be if the shift expression
			// were replaced by its left operand alone.".
			//
			// Delay operand checking until we know the final type
			// by marking the lhs expression as lhs shift operand.
			//
			// Usually (in correct programs), the lhs expression
			// is in the untyped map. However, it is possible to
			// create incorrect programs where the same expression
			// is evaluated twice (via a declaration cycle) such
			// that the lhs expression type is determined in the
			// first round and thus deleted from the map, and then
			// not found in the second round (double insertion of
			// the same expr node still just leads to one entry for
			// that node, and it can only be deleted once).
			// Be cautious and check for presence of entry.
			// Example: var e, f = int(1<<""[f]) // issue 11347
			if info, found := check.untyped[x.expr]; found {
				info.isLhs = true
				check.untyped[x.expr] = info
			}
			// keep x's type
			x.mode = value
			return
		}
	}

	// constant rhs must be >= 0
	if y.mode == constant_ && constant.Sign(y.val) < 0 {
		check.invalidOp(y.pos(), "shift count %s must not be negative", y)
	}

	// non-constant shift - lhs must be an integer
	if !isInteger(x.typ) {
		check.invalidOp(x.pos(), "shifted operand %s must be integer", x)
		x.mode = invalid
		return
	}

	x.mode = value
}
Example #3
0
File: expr.go Project: tcard/sgo
// representableConst reports whether x can be represented as
// value of the given basic type and for the configuration
// provided (only needed for int/uint sizes).
//
// If rounded != nil, *rounded is set to the rounded value of x for
// representable floating-point and complex values, and to an Int
// value for integer values; it is left alone otherwise.
// It is ok to provide the addressof the first argument for rounded.
func representableConst(x constant.Value, conf *Config, typ *Basic, rounded *constant.Value) bool {
	if x.Kind() == constant.Unknown {
		return true // avoid follow-up errors
	}

	switch {
	case isInteger(typ):
		x := constant.ToInt(x)
		if x.Kind() != constant.Int {
			return false
		}
		if rounded != nil {
			*rounded = x
		}
		if x, ok := constant.Int64Val(x); ok {
			switch typ.kind {
			case Int:
				var s = uint(conf.sizeof(typ)) * 8
				return int64(-1)<<(s-1) <= x && x <= int64(1)<<(s-1)-1
			case Int8:
				const s = 8
				return -1<<(s-1) <= x && x <= 1<<(s-1)-1
			case Int16:
				const s = 16
				return -1<<(s-1) <= x && x <= 1<<(s-1)-1
			case Int32:
				const s = 32
				return -1<<(s-1) <= x && x <= 1<<(s-1)-1
			case Int64, UntypedInt:
				return true
			case Uint, Uintptr:
				if s := uint(conf.sizeof(typ)) * 8; s < 64 {
					return 0 <= x && x <= int64(1)<<s-1
				}
				return 0 <= x
			case Uint8:
				const s = 8
				return 0 <= x && x <= 1<<s-1
			case Uint16:
				const s = 16
				return 0 <= x && x <= 1<<s-1
			case Uint32:
				const s = 32
				return 0 <= x && x <= 1<<s-1
			case Uint64:
				return 0 <= x
			default:
				unreachable()
			}
		}
		// x does not fit into int64
		switch n := constant.BitLen(x); typ.kind {
		case Uint, Uintptr:
			var s = uint(conf.sizeof(typ)) * 8
			return constant.Sign(x) >= 0 && n <= int(s)
		case Uint64:
			return constant.Sign(x) >= 0 && n <= 64
		case UntypedInt:
			return true
		}

	case isFloat(typ):
		x := constant.ToFloat(x)
		if x.Kind() != constant.Float {
			return false
		}
		switch typ.kind {
		case Float32:
			if rounded == nil {
				return fitsFloat32(x)
			}
			r := roundFloat32(x)
			if r != nil {
				*rounded = r
				return true
			}
		case Float64:
			if rounded == nil {
				return fitsFloat64(x)
			}
			r := roundFloat64(x)
			if r != nil {
				*rounded = r
				return true
			}
		case UntypedFloat:
			return true
		default:
			unreachable()
		}

	case isComplex(typ):
		x := constant.ToComplex(x)
		if x.Kind() != constant.Complex {
			return false
		}
		switch typ.kind {
		case Complex64:
			if rounded == nil {
				return fitsFloat32(constant.Real(x)) && fitsFloat32(constant.Imag(x))
			}
			re := roundFloat32(constant.Real(x))
			im := roundFloat32(constant.Imag(x))
			if re != nil && im != nil {
				*rounded = constant.BinaryOp(re, token.ADD, constant.MakeImag(im))
				return true
			}
		case Complex128:
			if rounded == nil {
				return fitsFloat64(constant.Real(x)) && fitsFloat64(constant.Imag(x))
			}
			re := roundFloat64(constant.Real(x))
			im := roundFloat64(constant.Imag(x))
			if re != nil && im != nil {
				*rounded = constant.BinaryOp(re, token.ADD, constant.MakeImag(im))
				return true
			}
		case UntypedComplex:
			return true
		default:
			unreachable()
		}

	case isString(typ):
		return x.Kind() == constant.String

	case isBoolean(typ):
		return x.Kind() == constant.Bool
	}

	return false
}