Hi,
When using cgo its my understanding that strings created with C.CString
must be freed with C.free, but yet numeric types do not need to be
explicitly freed.
Firstly, is CString a special case here, or are there other types that need
to be explicitly freed as well?
Secondly, Im writing a lot of wrappers to cgo functions that will requiring
converting go 'string' arguments in the outer function, into C.String
arguments in the cgo inner function. Im looking for a simple way to ensure
that I dont create any memory leaks. In view of this I have an idea to wrap
the CString in a go struct and set the finalizer to free the CString :
// -------------------------------------- wrapped.go
--------------------------------------
package golasso
import (
// #include <stdlib.h>
"C"
"fmt"
"runtime"
"unsafe"
)
type WrappedString struct {
s *C.char
}
func FreeWrappedString(s *WrappedString) {
fmt.Print("Freeing WrappedString")
C.free(unsafe.Pointer(s.s))
}
func NewWrappedString(s string) WrappedString {
wrappedString := WrappedString{s: C.CString(s)}
runtime.SetFinalizer(&wrappedString, FreeWrappedString)
return wrappedString
}
// --------------------------------------
func simulatedCCall(s *C.char) {
fmt.Print("simulated C call")
}
// -------------------------------------- wrapped_test.go
--------------------------------------
package golasso
import (
"runtime"
"testing"
)
func TestWrapped(t *testing.T) {
simulatedCCall(NewWrappedString("fred").s)
t.Logf("simulated C call")
runtime.GC()
}
NB: I do realise that, in a production scenario, it might be a long time
before the GC runs and therefore a long time before the GC calls the
finalizer to free the CString. Im not so worried about this, as my primary
concern is ensuring that *every* CString is definitely going to be freed at
some point, and therefore I have no *true* memory leaks.
What are the pros/cons of this? Is it even correct? Is there an easier way
to achieve this?
Andy
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
