24b5375636
In some cases, the global character of a value was lost, leading to undefined behaviour. Now a node level field of -1 means that the value is global, and that it should be accessed from the root data frame. Fixes #993.
235 lines
6.7 KiB
Go
235 lines
6.7 KiB
Go
package interp
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import (
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"log"
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"reflect"
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"strconv"
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)
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// A sKind represents the kind of symbol.
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type sKind uint
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// Symbol kinds for the Go interpreter.
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const (
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undefSym sKind = iota
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binSym // Binary from runtime
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bltnSym // Builtin
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constSym // Constant
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funcSym // Function
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labelSym // Label
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pkgSym // Package
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typeSym // Type
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varSym // Variable
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)
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var symKinds = [...]string{
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undefSym: "undefSym",
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binSym: "binSym",
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bltnSym: "bltnSym",
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constSym: "constSym",
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funcSym: "funcSym",
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labelSym: "labelSym",
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pkgSym: "pkgSym",
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typeSym: "typeSym",
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varSym: "varSym",
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}
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func (k sKind) String() string {
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if k < sKind(len(symKinds)) {
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return symKinds[k]
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}
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return "SymKind(" + strconv.Itoa(int(k)) + ")"
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}
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// A symbol represents an interpreter object such as type, constant, var, func,
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// label, builtin or binary object. Symbols are defined within a scope.
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type symbol struct {
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kind sKind
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typ *itype // Type of value
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node *node // Node value if index is negative
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from []*node // list of nodes jumping to node if kind is label, or nil
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recv *receiver // receiver node value, if sym refers to a method
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index int // index of value in frame or -1
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rval reflect.Value // default value (used for constants)
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builtin bltnGenerator // Builtin function or nil
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global bool // true if symbol is defined in global space
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}
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// scope type stores symbols in maps, and frame layout as array of types
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// The purposes of scopes are to manage the visibility of each symbol
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// and to store the memory frame layout information (type and index in frame)
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// at each level (global, package, functions)
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//
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// scopes are organized in a stack fashion: a first scope (universe) is created
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// once at global level, and for each block (package, func, for, etc...), a new
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// scope is pushed at entry, and poped at exit.
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//
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// Nested scopes with the same level value use the same frame: it allows to have
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// exactly one frame per function, with a fixed position for each variable (named
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// or not), no matter the inner complexity (number of nested blocks in the function)
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//
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// In symbols, the index value corresponds to the index in scope.types, and at
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// execution to the index in frame, created exactly from the types layout.
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//
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type scope struct {
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anc *scope // ancestor upper scope
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child []*scope // included scopes
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def *node // function definition node this scope belongs to, or nil
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loop *node // loop exit node for break statement
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loopRestart *node // loop restart node for continue statement
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pkgID string // unique id of package in which scope is defined
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types []reflect.Type // frame layout, may be shared by same level scopes
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level int // frame level: number of frame indirections to access var during execution
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sym map[string]*symbol // map of symbols defined in this current scope
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global bool // true if scope refers to global space (single frame for universe and package level scopes)
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iota int // iota value in this scope
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}
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// push creates a new child scope and chain it to the current one.
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func (s *scope) push(indirect bool) *scope {
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sc := &scope{anc: s, level: s.level, sym: map[string]*symbol{}}
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s.child = append(s.child, sc)
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if indirect {
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sc.types = []reflect.Type{}
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sc.level = s.level + 1
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} else {
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// Propagate size, types, def and global as scopes at same level share the same frame.
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sc.types = s.types
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sc.def = s.def
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sc.global = s.global
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sc.level = s.level
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}
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// inherit loop state and pkgID from ancestor
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sc.loop, sc.loopRestart, sc.pkgID = s.loop, s.loopRestart, s.pkgID
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return sc
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}
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func (s *scope) pushBloc() *scope { return s.push(false) }
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func (s *scope) pushFunc() *scope { return s.push(true) }
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func (s *scope) pop() *scope {
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if s.level == s.anc.level {
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// Propagate size and types, as scopes at same level share the same frame.
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s.anc.types = s.types
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}
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return s.anc
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}
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func (s *scope) upperLevel() *scope {
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level := s.level
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for s != nil && s.level == level {
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s = s.anc
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}
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return s
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}
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// lookup searches for a symbol in the current scope, and upper ones if not found
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// it returns the symbol, the number of indirections level from the current scope
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// and status (false if no result).
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func (s *scope) lookup(ident string) (*symbol, int, bool) {
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level := s.level
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for {
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if sym, ok := s.sym[ident]; ok {
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if sym.global {
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return sym, globalFrame, true
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}
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return sym, level - s.level, true
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}
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if s.anc == nil {
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break
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}
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s = s.anc
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}
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return nil, 0, false
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}
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// lookdown searches for a symbol in the current scope and included ones, recursively.
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// It returns the first found symbol and true, or nil and false.
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func (s *scope) lookdown(ident string) (*symbol, bool) {
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if sym, ok := s.sym[ident]; ok {
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return sym, true
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}
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for _, c := range s.child {
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if sym, ok := c.lookdown(ident); ok {
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return sym, true
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}
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}
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return nil, false
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}
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func (s *scope) rangeChanType(n *node) *itype {
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if sym, _, found := s.lookup(n.child[1].ident); found {
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if t := sym.typ; len(n.child) == 3 && t != nil && (t.cat == chanT || t.cat == chanRecvT) {
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return t
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}
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}
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c := n.child[1]
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if c.typ == nil {
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return nil
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}
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switch {
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case c.typ.cat == chanT, c.typ.cat == chanRecvT:
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return c.typ
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case c.typ.cat == valueT && c.typ.rtype.Kind() == reflect.Chan:
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return &itype{cat: chanT, val: &itype{cat: valueT, rtype: c.typ.rtype.Elem()}}
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}
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return nil
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}
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// fixType returns the input type, or a valid default type for untyped constant.
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func (s *scope) fixType(t *itype) *itype {
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if !t.untyped || t.cat != valueT {
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return t
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}
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switch typ := t.TypeOf(); typ.Kind() {
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case reflect.Int64:
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return s.getType("int")
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case reflect.Uint64:
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return s.getType("uint")
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case reflect.Float64:
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return s.getType("float64")
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case reflect.Complex128:
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return s.getType("complex128")
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}
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return t
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}
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func (s *scope) getType(ident string) *itype {
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var t *itype
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if sym, _, found := s.lookup(ident); found {
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if sym.kind == typeSym {
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t = sym.typ
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}
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}
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return t
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}
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// add adds a type to the scope types array, and returns its index.
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func (s *scope) add(typ *itype) (index int) {
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if typ == nil {
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log.Panic("nil type")
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}
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index = len(s.types)
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t := typ.frameType()
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if t == nil {
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log.Panic("nil reflect type")
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}
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s.types = append(s.types, t)
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return
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}
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func (interp *Interpreter) initScopePkg(pkgID string) *scope {
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sc := interp.universe
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interp.mutex.Lock()
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if _, ok := interp.scopes[pkgID]; !ok {
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interp.scopes[pkgID] = sc.pushBloc()
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}
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sc = interp.scopes[pkgID]
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sc.pkgID = pkgID
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interp.mutex.Unlock()
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return sc
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}
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