Re: [go-nuts] About 64bits alignment

On Sat, Jan 26, 2019 at 7:56 AM Marvin Renich wrote: > > * Ian Lance Taylor [190125 18:11]: > > On Fri, Jan 25, 2019 at 2:59 PM wrote: > > > I still can't find anything "authoritative and unambiguous" on this. > > > Therefore apps are going to be released with bugs in them. Can > > > someone pl

Re: [go-nuts] About 64bits alignment

* Ian Lance Taylor [190125 18:11]: > On Fri, Jan 25, 2019 at 2:59 PM wrote: > > I still can't find anything "authoritative and unambiguous" on this. > > Therefore apps are going to be released with bugs in them. Can > > someone please say specifically when it is _not_ safe to use 64-bit > > atom

Re: [go-nuts] About 64bits alignment

On Fri, Jan 25, 2019 at 2:59 PM wrote: > > I still can't find anything "authoritative and unambiguous" on this. > Therefore apps are going to be released with bugs in them. Can someone > please say specifically when it is _not_ safe to use 64-bit atomic operations? > > When it is unsafe on a 6

Re: [go-nuts] About 64bits alignment

I still can't find anything "authoritative and unambiguous" on this. Therefore apps are going to be released with bugs in them. Can someone please say specifically when it is _not_ safe to use 64-bit atomic operations? When it is unsafe on a 64-bit OS? When it is unsafe on a 32-bit OS? John

Re: [go-nuts] About 64bits alignment

On Thursday, March 15, 2018 at 12:54:22 PM UTC-4, Ian Lance Taylor wrote: > > On Thu, Mar 15, 2018 at 8:11 AM, T L > > wrote: > > > > On Thursday, March 15, 2018 at 10:57:50 AM UTC-4, Jan Mercl wrote: > >> > >> > >> On Thu, Mar 15, 2018 at 3:29 PM T L wrote: > >> > >> > I mean "always ma

Re: [go-nuts] About 64bits alignment

On Thu, Mar 15, 2018 at 8:11 AM, T L wrote: > > On Thursday, March 15, 2018 at 10:57:50 AM UTC-4, Jan Mercl wrote: >> >> >> On Thu, Mar 15, 2018 at 3:29 PM T L wrote: >> >> > I mean "always makes 64-bit words 64-bit aligned on i386 OSes." >> >> AFAIK, that's not the case, ie. not always. >> >> --

Re: [go-nuts] About 64bits alignment

On Thursday, March 15, 2018 at 10:57:50 AM UTC-4, Jan Mercl wrote: > > > On Thu, Mar 15, 2018 at 3:29 PM T L > > wrote: > > > I mean "always makes 64-bit words 64-bit aligned on i386 OSes." > > AFAIK, that's not the case, ie. not always. > > -- > > -j > But it looks the results from Go playgro

Re: [go-nuts] About 64bits alignment

On Thu, Mar 15, 2018 at 3:29 PM T L wrote: > I mean "always makes 64-bit words 64-bit aligned on i386 OSes." AFAIK, that's not the case, ie. not always. -- -j -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group an

Re: [go-nuts] About 64bits alignment

On Thursday, March 15, 2018 at 10:09:36 AM UTC-4, T L wrote: > > > > On Monday, February 6, 2017 at 7:43:33 AM UTC-5, T L wrote: >> >> >> >> On Monday, February 6, 2017 at 11:16:22 AM UTC, T L wrote: >>> >>> >>> >>> On Monday, February 6, 2017 at 6:43:04 PM UTC+8, T L wrote: O

Re: [go-nuts] About 64bits alignment

On Monday, February 6, 2017 at 7:43:33 AM UTC-5, T L wrote: > > > > On Monday, February 6, 2017 at 11:16:22 AM UTC, T L wrote: >> >> >> >> On Monday, February 6, 2017 at 6:43:04 PM UTC+8, T L wrote: >>> >>> >>> >>> On Monday, February 6, 2017 at 3:14:22 AM UTC+8, Ian Lance Taylor wrote:

Re: [go-nuts] About 64bits alignment

On Monday, February 6, 2017 at 11:16:22 AM UTC, T L wrote: > > > > On Monday, February 6, 2017 at 6:43:04 PM UTC+8, T L wrote: >> >> >> >> On Monday, February 6, 2017 at 3:14:22 AM UTC+8, Ian Lance Taylor wrote: >>> >>> On Sun, Feb 5, 2017 at 10:52 AM, T L wrote: >>> > Ian, thanks for the answe

Re: [go-nuts] About 64bits alignment

On Monday, February 6, 2017 at 6:43:04 PM UTC+8, T L wrote: > > > > On Monday, February 6, 2017 at 3:14:22 AM UTC+8, Ian Lance Taylor wrote: >> >> On Sun, Feb 5, 2017 at 10:52 AM, T L wrote: >> > Ian, thanks for the answers. >> > >> > But I still not very confirm on many points. >> > >> > U

Re: [go-nuts] About 64bits alignment

On Monday, February 6, 2017 at 3:14:22 AM UTC+8, Ian Lance Taylor wrote: > > On Sun, Feb 5, 2017 at 10:52 AM, T L > > wrote: > > Ian, thanks for the answers. > > > > But I still not very confirm on many points. > > > > Up to now, there are two places mention the alignments in Go. > > > >

Re: [go-nuts] About 64bits alignment

On Monday, February 6, 2017 at 12:44:38 PM UTC+8, Ian Lance Taylor wrote: > > On Sun, Feb 5, 2017 at 8:15 PM, T L > > wrote: > > > > In fact, I still have another question needs to be clarify: what does > the > > "word" in "The first word in a global variable or in an allocated struct > or

Re: [go-nuts] About 64bits alignment

On Sun, Feb 5, 2017 at 8:15 PM, T L wrote: > > In fact, I still have another question needs to be clarify: what does the > "word" in "The first word in a global variable or in an allocated struct or > slice" mean? > A field with the same length with int values? In this case it means a 64-bit valu

Re: [go-nuts] About 64bits alignment

On Sun, Feb 5, 2017 at 11:55 AM, T L wrote: > > In short, when structs and slices are used as the non-first fields of other > structs, > then the struct and slice fields may be not 64bit aligned on 32bit OSes. > > But what about arrays? Can the first word in an allocated array be relied > upon to

Re: [go-nuts] About 64bits alignment

On Monday, February 6, 2017 at 3:55:35 AM UTC+8, T L wrote: > > > > On Monday, February 6, 2017 at 3:14:22 AM UTC+8, Ian Lance Taylor wrote: >> >> On Sun, Feb 5, 2017 at 10:52 AM, T L wrote: >> > Ian, thanks for the answers. >> > >> > But I still not very confirm on many points. >> > >> > U

Re: [go-nuts] About 64bits alignment

On Monday, February 6, 2017 at 3:14:22 AM UTC+8, Ian Lance Taylor wrote: > > On Sun, Feb 5, 2017 at 10:52 AM, T L > > wrote: > > Ian, thanks for the answers. > > > > But I still not very confirm on many points. > > > > Up to now, there are two places mention the alignments in Go. > > > >

Re: [go-nuts] About 64bits alignment

On Sun, Feb 5, 2017 at 10:52 AM, T L wrote: > Ian, thanks for the answers. > > But I still not very confirm on many points. > > Up to now, there are two places mention the alignments in Go. > > The first is in the end of Go spec: > > > Size and alignment guarantees > > For the numeric types, the f

Re: [go-nuts] About 64bits alignment

Ian, thanks for the answers. But I still not very confirm on many points. Up to now, there are two places mention the alignments in Go. The first is in the end of Go spec: Size and alignment guarantees For the numeric types , the following sizes ar

Re: [go-nuts] About 64bits alignment

On Sat, Feb 4, 2017 at 2:38 PM, Axel Wagner wrote: > On Sat, Feb 4, 2017 at 11:13 PM, Ian Lance Taylor wrote: >> >> The spec does not say that unsafe.Alignof(s.B) will return 8. In >> fact, on 32-bit targets, with the gc toolchain, it will return 4. > > > To me, that seems to contradict the comb

Re: [go-nuts] About 64bits alignment

On Sat, Feb 4, 2017 at 11:13 PM, Ian Lance Taylor wrote: > On Sat, Feb 4, 2017 at 7:33 AM, Axel Wagner > wrote: > > > > I believe, that fields do not necessarily need to be properly aligned > > (explaining 599). However, *structs* have a necessary alignment, as > required > > by their fields. So

Re: [go-nuts] About 64bits alignment

Basically, to most of your disagreements: I'm wildly guessing, trying to make sense of the information I do have :) Just one specific answer: On Sat, Feb 4, 2017 at 11:05 PM, Matt Harden wrote: > > Wait, I don't think you've explained why expvar.Float would be aligned > even if embedded in anothe

Re: [go-nuts] About 64bits alignment

On Sat, Feb 4, 2017 at 7:33 AM, Axel Wagner wrote: > > I believe, that fields do not necessarily need to be properly aligned > (explaining 599). However, *structs* have a necessary alignment, as required > by their fields. So, if you do > type S struct { > A uint32 > B uint64 > } > then th

Re: [go-nuts] About 64bits alignment

On Sat, Feb 4, 2017 at 7:34 AM 'Axel Wagner' via golang-nuts < golang-nuts@googlegroups.com> wrote: > I find this an inappropriate answer. Yes, they need care, but it should at > least be possible to figure out how to use them from reading documentation > (carefully). I tend to agree, that neither

Re: [go-nuts] About 64bits alignment

I find this an inappropriate answer. Yes, they need care, but it should at least be possible to figure out how to use them from reading documentation (carefully). I tend to agree, that neither the spec nor the documentation of the atomic package is particularly helpful about these questions; at lea

Re: [go-nuts] About 64bits alignment

On Sat, Feb 04, 2017 at 01:30:49AM -0800, T L wrote: > Get it. This is quite bug prone to write programs on 64bit OSes and the > programs are expected to run on 32bit OSes too. Well, there's a reason the sync/atomic package docs have this statement right at the top: > These functions require gre

Re: [go-nuts] About 64bits alignment

On Saturday, February 4, 2017 at 6:32:52 PM UTC+8, Axel Wagner wrote: > > The spec says this: > https://golang.org/ref/spec#Size_and_alignment_guarantees > Now, I can't really read from this whether this applies to fields or not. > If it does, it would seem to me, that, indeed, WaitGroup wouldn

Re: [go-nuts] About 64bits alignment

The spec says this: https://golang.org/ref/spec#Size_and_alignment_guarantees Now, I can't really read from this whether this applies to fields or not. If it does, it would seem to me, that, indeed, WaitGroup wouldn't need to use the trick it does. For the example you name: It isn't particularly t

Re: [go-nuts] About 64bits alignment

On Saturday, February 4, 2017 at 2:18:44 PM UTC+8, Matt Harden wrote: > > https://play.golang.org/p/VWysBwbPCu > > The above program prints 64-bit aligned addresses on the playground, but > that's a 64 bit platform (with 32 bit pointers). On a 32 bit platform x.j > is not guaranteed to be 64-bi

Re: [go-nuts] About 64bits alignment

On Saturday, February 4, 2017 at 5:56:30 PM UTC+8, T L wrote: > > > > On Saturday, February 4, 2017 at 5:40:25 PM UTC+8, T L wrote: >> >> >> >> 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 wrote: >>> > Why does WaitGroup.s

Re: [go-nuts] About 64bits alignment

On Saturday, February 4, 2017 at 5:40:25 PM UTC+8, T L wrote: > > > > 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 wrote: >> > Why does WaitGroup.state method check 64-bit alignment at run time? >> > Why not make the state

Re: [go-nuts] About 64bits alignment

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 > > 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://gola

Re: [go-nuts] About 64bits alignment

On Saturday, February 4, 2017 at 2:51:53 PM UTC+8, Axel Wagner wrote: > > On Sat, Feb 4, 2017 at 5:49 AM, T L > > wrote: > >> On Saturday, February 4, 2017 at 11:03:11 AM UTC+8, Matt Harden wrote: >>> >>> Never mind; I just realized that a WaitGroup is not necessarily at the >>> start of an all

Re: [go-nuts] About 64bits alignment

On Sat, Feb 4, 2017 at 5:49 AM, T L wrote: > On Saturday, February 4, 2017 at 11:03:11 AM UTC+8, Matt Harden wrote: >> >> Never mind; I just realized that a WaitGroup is not necessarily at the >> start of an allocation or global variable. >> > > Not very get it. > Do you mean WaitGroup will be em

Re: [go-nuts] About 64bits alignment

https://play.golang.org/p/VWysBwbPCu The above program prints 64-bit aligned addresses on the playground, but that's a 64 bit platform (with 32 bit pointers). On a 32 bit platform x.j is not guaranteed to be 64-bit aligned. The same would be true if we substituted a WaitGroup for int64 in that exa

Re: [go-nuts] About 64bits alignment

On Saturday, February 4, 2017 at 11:03:11 AM UTC+8, Matt Harden wrote: > > Never mind; I just realized that a WaitGroup is not necessarily at the > start of an allocation or global variable. > Not very get it. Do you mean WaitGroup will be embedded in other types? So we can't use the 64bit atom

Re: [go-nuts] About 64bits alignment

Never mind; I just realized that a WaitGroup is not necessarily at the start of an allocation or global variable. On Fri, Feb 3, 2017 at 7:01 PM Matt Harden wrote: > Doesn't the statement "32-bit compilers to not ensure [64 bit alignment at > the start of an allocation]" contradict the sync/atom

Re: [go-nuts] About 64bits alignment

Doesn't the statement "32-bit compilers to not ensure [64 bit alignment at the start of an allocation]" contradict the sync/atomic statement "The first word in a global variable or in an allocated struct or slice can be relied upon to be 64-bit aligned."? On Fri, Feb 3, 2017 at 6:44 AM Ian Lance T

Re: [go-nuts] About 64bits alignment

On Fri, Feb 3, 2017 at 5:38 AM, T L 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 > > /

Re: [go-nuts] About 64bits alignment

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, lo

Re: [go-nuts] About 64bits alignment

On Thursday, February 2, 2017 at 12:11:39 AM UTC+8, Jan Mercl wrote: > > On Wed, Feb 1, 2017 at 5:04 PM T L > > wrote: > > > But what does an allocated struct or slice means? A struct or slice > allocated on heap, not stack? > > There's no heap nor stack from the POV of the language spec. Alloc

Re: [go-nuts] About 64bits alignment

On Wed, Feb 1, 2017 at 5:04 PM T L wrote: > But what does an allocated struct or slice means? A struct or slice allocated on heap, not stack? There's no heap nor stack from the POV of the language spec. Allocated means appropriate amount of storage is now used by the instance. Everything else is

[go-nuts] About 64bits alignment

the sync/atomic docs, https://golang.org/pkg/sync/atomic/, says in the end of the docs On x86-32, the 64-bit functions use instructions unavailable before the > Pentium MMX. > On non-Linux ARM, the 64-bit functions use instructions unavailable before > the ARMv6k core. > > On both ARM and x8