s/same/safe/ The question is about whether it's safe to do the same conversion outside of the Go runtime.
On Friday, June 19, 2020 at 10:04:01 PM UTC+3, Iskander Sharipov wrote: > > Hello! > > https://golang.org/src/runtime/symtab.go?s=7594:7745#L244 > > type Func struct { > > opaque struct{} // unexported field to disallow conversions > > } > > > func (f *Func) raw() *_func { > > return (*_func)(unsafe.Pointer(f)) > > } > > > An empty struct Func (T1) is converted to a non-zero struct _func (T2). > > From the unsafe.Pointer documentation ( > https://golang.org/pkg/unsafe/#Pointer): > > > T1->T2 conversion is safe if T2 is no larger than T1 ... (shortened for > clarity) > > I'm guessing that documentation probably meant "allocation size", not the > "static type size"? > T1 pointer can be obtained from the T2 allocation, so it's allocation size > can be different from the unsafe.Sizeof(T1{}). > > Or it could be that runtime can violate that particular rule. > > *My question*: is it same to convert T1<->T2 even if > sizeof(T1)<sizeof(T2), but the memory was allocated for the bigger object? > > Thank you in advance. > > > > -- 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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/aff200fb-cbc9-44a1-a009-f8f9965fefefo%40googlegroups.com.
