On Tue, Jan 31, 2017 at 10:59 PM, Eliot Hedeman
<eliot.d.hede...@gmail.com> wrote:
> It may not be the most elegant solution, but you could possibly check for
> the high bit set on any pointer during GC. If the high bit is set, you know
> for sure that that pointer is not actually pointing to anything, but rather
> is data. Technically speaking, the top 16 bits of any pointer in x86-64 is
> completely ignored
> by the cpu, So To make this work, you would have to change the order of the
> stringStruct to be { len int, str unsafe.Pointer}, but the principle is the
> same, the last 8 bits could be used the exact same way.1) Go runs on processors other than x86_64. 2) Even on x86_64, Solaris, for example, sign extends the stack addresses, so the top 16 bits are not completely ignored by the OS. Ian > On Tuesday, January 31, 2017 at 9:15:54 PM UTC-8, Ian Lance wrote: >> >> On Tue, Jan 31, 2017 at 9:10 PM, Eliot Hedeman >> <eliot.d...@gmail.com> wrote: >> > I was writing up a proposal about adding the small string >> > optimization(putting strings on the heap if they will fit within the >> > sringStruct)to the go runtime, and I realized there might be good reason >> > why >> > this has not been done yet. Are there any glaring reasons you can think >> > of? >> > Here is the really rough draft of the proposal. Thanks for the feedback! >> >> The problem is that the concurrent garbage collector needs to be able >> to determine reliably and safely whether a word in memory, including >> on the stack, contains a pointer or not. It's not OK to have a word >> in memory that might or might contain a pointer. It's a good thing >> that Go doesn't have unions in the language, because they would be >> very difficult to implement in the garbage collector. >> >> Ian > > -- > 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. -- 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.
