On Friday, February 3, 2017 at 10:44:26 PM UTC+8, Ian Lance Taylor wrote: > > On Fri, Feb 3, 2017 at 5:38 AM, T L <tapi...@gmail.com <javascript:>> > wrote: > > Why does WaitGroup.state method check 64-bit alignment at run time? > > Why not make the state field as the first word of WaitGroup struct? > > > > // https://golang.org/src/sync/waitgroup.go?s=1857:1892#L20 > > > > type WaitGroup struct { > > > > noCopy noCopy > > > > // 64-bit value: high 32 bits are counter, low 32 bits are waiter count. > > > > // 64-bit atomic operations require 64-bit alignment, but 32-bit > > > > // compilers do not ensure it. So we allocate 12 bytes and then use > > > > // the aligned 8 bytes in them as state. > > Doesn't this comment explain the problem? > > Ian >
Part of. Ok I get it now. BTW, I have another question, can an allocated local int64 value be relied upon to be 64-bit aligned? -- 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.
