Documentation
¶
Overview ¶
Package vm executes compiled Kukel programs on a stack machine.
Each call has a frame. A frame's slots (parameters, locals, hidden slots) sit on the value stack at frame.base, followed by its operand stack. The callee value sits just below the slots.
Index ¶
- Constants
- type Builtins
- type Canceller
- type DebugFrame
- type DebugVar
- type RuntimeError
- type TraceEntry
- type VM
- func (vm *VM) BuiltinLookup() Builtins
- func (vm *VM) Call(fn value.Value, args []value.Value) (value.Value, error)
- func (vm *VM) Cancellable() *Canceller
- func (vm *VM) CloseOutput()
- func (vm *VM) Config() *native.Config
- func (vm *VM) CurrentCanceller() *Canceller
- func (vm *VM) Done() <-chan struct{}
- func (vm *VM) Err() error
- func (vm *VM) Extend(prog *bytecode.Program) error
- func (vm *VM) Frames() []DebugFrame
- func (vm *VM) Global(name string) (value.Value, bool)
- func (vm *VM) Init() error
- func (vm *VM) Local(key any, init func() any) any
- func (vm *VM) Program() *bytecode.Program
- func (vm *VM) Rand() *rand.Rand
- func (vm *VM) ResetSteps()
- func (vm *VM) Run(args []string) (int, error)
- func (vm *VM) SetStderr(w io.Writer)
- func (vm *VM) ShareCanceller(c *Canceller)
- func (vm *VM) ShareOutput() (stdout, stderr io.Writer)
- func (vm *VM) Start(fn value.Value, args []value.Value) (value.Value, error)
- func (vm *VM) Started() time.Time
- func (vm *VM) Stderr() io.Writer
- func (vm *VM) Stdin() *bufio.Reader
- func (vm *VM) Stdout() io.Writer
- func (vm *VM) Thrown(err error) (value.Value, bool)
- func (vm *VM) Vars(i int) []DebugVar
Constants ¶
const MaxFrames = 10000
MaxFrames bounds the call depth; deeper recursion is a stack overflow.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Builtins ¶
type Builtins func(name string) (*value.BuiltinObj, bool)
Builtins resolves built-in functions by name.
type Canceller ¶ added in v0.2.0
type Canceller struct {
// contains filtered or unexported fields
}
Canceller stops a running program from another goroutine. Cancellers form a tree: cancelling one cancels the ones made from it (Child).
func NewCanceller ¶ added in v0.2.1
func NewCanceller() *Canceller
NewCanceller makes a Canceller that nothing has cancelled yet.
func (*Canceller) Cancel ¶ added in v0.2.0
Cancel makes the programs that use c (and its children) stop at their next step with a CancelledError that try cannot catch; Go functions that wait (sleep, receive) return at once. It may be called from any goroutine, and more than once.
func (*Canceller) Child ¶ added in v0.2.1
Child makes a Canceller that is cancelled when c is (at once if c already is).
type DebugFrame ¶ added in v0.15.0
type DebugFrame struct {
Func *bytecode.Function
Line int // the line it is at (where it called the next frame)
This *value.ObjectObj // the object of a member function call, or nil
}
DebugFrame is a call the program is in, for the debugger.
type DebugVar ¶ added in v0.15.0
DebugVar is a variable of a frame: a parameter, local or captured one.
type RuntimeError ¶
type RuntimeError struct {
Value value.Value // the thrown Error object (nil for the step limit, cancellation, exit)
Kind string // its kind (never "": an empty kind becomes the class name)
Msg string // its message ("" without one)
Trace []TraceEntry // innermost call first
Fatal bool // try cannot catch it (exit, the step limit, cancellation)
Exit *int // set by exit(code): not an error, the program ends
}
RuntimeError is a thrown exception: the thrown value and the stack trace at the throw. It is what Run returns for an exception nobody caught.
func (*RuntimeError) Error ¶
func (e *RuntimeError) Error() string
Error returns the message and the stack trace. Long traces (deep recursion) show only the first and last traceEnds calls.
type TraceEntry ¶
TraceEntry is one line of a stack trace.
type VM ¶
type VM struct {
// StepLimit, when positive, stops the program with a fatal error after
// that many backward jumps, calls of Kukel functions and thrown
// exceptions: for tests, and for Go programs that run untrusted code
// (the kukel package resets the count for every call from Go).
StepLimit int
// Debug, when set, runs at every BREAK instruction: at the start of each
// source line of code that the debugger made a copy of (Debuggable).
// The VM's frames are then as at the start of that line (Frames). An
// error stops the program (a fatal one, such as exit, ends it).
Debug func(vm *VM) error
// contains filtered or unexported fields
}
VM runs one program.
func New ¶
New prepares prog for running: it binds the functions and built-ins to their global slots.
func NewWith ¶ added in v0.2.0
func NewWith(prog *bytecode.Program, builtins Builtins, config *native.Config, stdout io.Writer, stdin io.Reader) (*VM, error)
NewWith is New for a program limited by config (see native.Config): it refuses a program that uses a built-in or module config does not allow.
func (*VM) BuiltinLookup ¶ added in v0.2.0
BuiltinLookup is how the VM found its built-ins (New's builtins).
func (*VM) Call ¶
Call calls fn from a built-in (sort's comparator, for example). The built-in's own arguments stay on the stack below the new call.
func (*VM) Cancellable ¶ added in v0.2.0
Cancellable makes the program cancellable from now on with the returned Canceller (replacing an earlier one). Workers started afterwards share it: cancelling the program cancels them too.
func (*VM) CloseOutput ¶ added in v0.2.1
func (vm *VM) CloseOutput()
CloseOutput flushes the output shared with workers (ShareOutput) and drops what they write later. Run does it when main returns.
func (*VM) CurrentCanceller ¶ added in v0.2.0
CurrentCanceller is the VM's Canceller, or nil.
func (*VM) Done ¶ added in v0.2.0
func (vm *VM) Done() <-chan struct{}
Done implements value.Env: closed when the program is cancelled (nil if it cannot be).
func (*VM) Err ¶ added in v0.2.0
Err implements value.Env: the error for a cancelled program, else nil.
func (*VM) Extend ¶ added in v0.7.0
Extend continues with prog, a program that adds to the VM's program (compiler.Session): globals, classes and functions after the ones the VM has, and member functions defined since for the classes it has. The values of the globals stay.
func (*VM) Frames ¶ added in v0.15.0
func (vm *VM) Frames() []DebugFrame
Frames gives the calls the program is in, outermost first; the last is the one at the BREAK the debug hook was called for.
func (*VM) Global ¶ added in v0.2.0
Global returns the value of the global called name: a top-level name of the program ("main"), or a module's ("util::f", "json::encode").
func (*VM) Init ¶ added in v0.2.0
Init runs the global initializers, the first time only. If they throw an exception, every later Init gives the same error: the globals are not usable. If the step limit or a cancellation stopped them, the next Init runs them again from the start.
func (*VM) ResetSteps ¶ added in v0.2.0
func (vm *VM) ResetSteps()
ResetSteps starts counting steps for StepLimit from zero again.
func (*VM) Run ¶
Run runs the global initializers, then main(args). It returns main's result as the exit code (an int result; anything else is 0).
When main returns, the program ends: if workers share the output (ShareOutput), it is flushed and closed, so that workers still running cannot write any more.
func (*VM) ShareCanceller ¶ added in v0.2.0
ShareCanceller makes vm stop when c is cancelled (for a worker).
func (*VM) ShareOutput ¶ added in v0.2.0
ShareOutput makes the VM's standard output and error safe to use from several goroutines (workers) and returns them; other VMs can write to them too. Calling it again gives the same writers.
func (*VM) Start ¶ added in v0.2.0
Start runs the global initializers, then calls fn(args...) and gives its result. With fn nil it calls main, with args[0] as its parameter if main has one. exit(code) gives a *RuntimeError with Exit set.
func (*VM) Stdout ¶
Stdout, Stderr, Stdin, Call, Rand, Started, Local, Thrown, Done and Err implement value.Env for the built-ins and the native modules.
Source Files