func newExceptionValue(s *C.mrb_state) *Exception {
if s.exc == nil {
panic("exception value init without exception")
}
arenaIndex := C.mrb_gc_arena_save(s)
defer C.mrb_gc_arena_restore(s, C.int(arenaIndex))
// Convert the RObject* to an mrb_value
value := C.mrb_obj_value(unsafe.Pointer(s.exc))
// Retrieve and convert backtrace to []string (avoiding reflection in Decode)
var backtrace []string
mrbBacktrace := newValue(s, C.mrb_exc_backtrace(s, value)).Array()
for i := 0; i < mrbBacktrace.Len(); i++ {
ln, _ := mrbBacktrace.Get(i)
backtrace = append(backtrace, ln.String())
}
// Extract file + line from first backtrace line
file := "Unknown"
line := 0
if len(backtrace) > 0 {
fileAndLine := strings.Split(backtrace[0], ":")
if len(fileAndLine) >= 2 {
file = fileAndLine[0]
line, _ = strconv.Atoi(fileAndLine[1])
}
}
result := newValue(s, value)
return &Exception{
MrbValue: result,
Message: result.String(),
File: file,
Line: line,
Backtrace: backtrace,
}
}
// This saves the index into the arena.
//
// Restore the arena index later by calling ArenaRestore.
//
// The arena is where objects returned by functions such as LoadString
// are stored. By saving the index and then later restoring it with
// ArenaRestore, these objects can be garbage collected. Otherwise, the
// objects will never be garbage collected.
//
// The recommended usage pattern for memory management is to save
// the arena index prior to any Ruby execution, to turn the resulting
// Ruby value into Go values as you see fit, then to restore the arena
// index so that GC can collect any values.
//
// Of course, when Close() is called, all objects in the arena are
// garbage collected anyways, so if you're only calling mruby for a short
// period of time, you might not have to worry about saving/restoring the
// arena.
func (m *Mrb) ArenaSave() ArenaIndex {
return ArenaIndex(C.mrb_gc_arena_save(m.state))
}