On Sat, Mar 13, 2021 at 10:26 PM rmfr <remus.clearwa...@gmail.com> wrote: > > Maybe the reason for such a strict rule on using cgo is just to take > precautions if our GC moves object in the future? And at that time, the > syscall implementation must be rewritten to add some codes to pinning the > objects used by each syscall from being moved. Am I correct?
Yes, exactly. There are special rules for syscall, and the Go project promises that syscall will keep working, including pinning pointers, and internal pointers, that are passed to syscalls. Ian > On Sunday, March 14, 2021 at 2:11:18 PM UTC+8 rmfr wrote: >> >> I am watching the implementation of syscall `writev` from >> [here](https://github.com/golang/sys/blob/bd2e13477e9c63125302cd9da2d61879c6aa1721/unix/zsyscall_linux.go#L1641), >> and comparing it with the >> [proposal](https://github.com/golang/proposal/blob/master/design/12416-cgo-pointers.md) >> of cgo. I found the rule applies on cgo and syscall is inconsistent. >> >> If the object could be moved during GC, then the code to implement `writev` >> is incorrect. Because GC could happen during the syscall and the byte slices >> kernel is using has been moved! :-( >> >> If the object may not be moved during GC, then the code to implement syscall >> `writev` is correct. But from the perspective of go runtime, cgo is just a >> kind of special "syscall", then the rule applies to cgo now is far too >> strict -- you simply couldn't call a C API like `writev` which takes array >> of byte slices as input arg (because the rule applies on cgo now only allow >> one input arg contains at most one go pointer). >> >> Maybe I have missed something, please correct me. Thanks a lot for your >> patient and kindness :-) > > -- > 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. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/57c3f2e9-e28c-43e3-b765-b33434b6d1f5n%40googlegroups.com. -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAOyqgcUBUgw55HMMDp68mSZPhHCyRBjoL9di%3DGffrUBmB_L6bQ%40mail.gmail.com.
