On Mon, Jan 8, 2018 at 5:28 PM, Justin Israel <justinisr...@gmail.com> wrote:
>
> I've got a cgo library that needed a pass of adding runtime.KeepAlive() to
> prevent crashes when passing C pointers into cgo calls. Today a similar
> crash occurred in one of my functions in the library that looks like the
> following:
>
> func (i *ImageBuf) ReadFormatCallback(force bool, convert TypeDesc, progress
> *ProgressCallback) error {
> var cbk unsafe.Pointer
> if progress != nil {
> cbk = unsafe.Pointer(progress)
> }
>
> ok := C.ImageBuf_read(i.ptr, 0, 0, C.bool(force), C.TypeDesc(convert),
> cbk)
> if !bool(ok) {
> return i.LastError()
> }
>
> return nil
> }
>
> I had not added a KeepAlive() call after the C function because I assumed
> the conditional usage of i.LastError() would keep it alive. Am I wrong in
> that assumption? Should I still have a KeepAlive() call here?
>
> This could be a completely unrelated crash, although it looks the same as
> the other SIGSEGV crashes that I had fixed.
It depends. If `i.LastError()` is inlined, then whether the call
keeps `i` alive or not depends on what the method does.
Ian
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