On Tue, Feb 1, 2011 at 8:45 PM, Andrew Gerrand <a...@google.com> wrote:
> We've just tagged a new Go release, release.2011-02-01. As usual, you
> can update by running:
>  hg pull
>  hg update release

> This release includes significant changes to channel operations and minor
> changes to the log package. Your code will require modification if it uses
> channels in non-blocking communications or the log package's Exit functions.

> Non-blocking channel operations have been removed from the language.
> The equivalent operations have always been possible using a select statement
> with a default clause.  If a default clause is present in a select, that clause
> will execute (only) if no other is ready, which allows one to avoid blocking on
> a communication.

> For example, the old non-blocking send operation,

>        if ch <- v {
>                // sent
>        } else {
>                // not sent
>        }

> should be rewritten as,

>        select {
>        case ch <- v:
>                // sent
>        default:
>                // not sent
>        }

> Similarly, this receive,

>        v, ok := <-ch
>        if ok {
>                // received
>        } else {
>                // not received
>        }

> should be rewritten as,

>        select {
>        case v := <-ch:
>                // received
>        default:
>                // not received
>        }

> This change is a prelude to redefining the 'comma-ok' syntax for a receive.
> In a later release, a receive expression will return the received value and an
> optional boolean indicating whether the channel has been closed. These changes
> are being made in two stages to prevent this semantic change from silently
> breaking code that uses 'comma-ok' with receives.
> There are no plans to have a boolean expression form for sends.

> Sends to a closed channel will panic immediately. Previously, an unspecified
> number of sends would fail silently before causing a panic.

> The log package's Exit, Exitf, and Exitln functions have been renamed Fatal,
> Fatalf, and Fatalln respectively. This brings them in line with the naming of
> the testing package.

> The port to the "tiny" operating system has been removed. It is unmaintained
> and untested. It was a toy to show that Go can run on raw hardware and it
> served its purpose. The source code will of course remain in the repository
> history, so it could be brought back if needed later.

> This release also changes some of the internal structure of the memory
> allocator in preparation for other garbage collector changes.
> If you run into problems, please let us know.
> There is one known issue that we are aware of but have not debugged yet:
>        http://code.google.com/p/go/issues/detail?id=1464&.

> Other changes in this release:
> * 5l: document -F, force it on old ARMs (software floating point emulation)
> * 6g: fix registerization of temporaries (thanks Eoghan Sherry),
>        fix uint64(uintptr(unsafe.Pointer(&x))).
> * 6l: Relocate CMOV* instructions (thanks Gustavo Niemeyer),
>        windows/amd64 port (thanks Wei Guangjing).
> * 8l: add PE dynexport, emit DWARF in Windows PE, and
>        code generation fixes (thanks Wei Guangjing).
> * bufio: make Flush a no-op when the buffer is empty.
> * bytes: Add Buffer.ReadBytes, Buffer.ReadString (thanks Evan Shaw).
> * cc: mode to generate go-code for types and variables.
> * cgo: define CGO_CFLAGS and CGO_LDFLAGS in Go files (thanks Gustavo Niemeyer),
>        windows/386 port (thanks Wei Guangjing).
> * codereview: fix windows (thanks Hector Chu),
>        handle file patterns better,
>        more ASCII vs. Unicode nonsense.
> * crypto/dsa: add support for DSA.
> * crypto/openpgp: add s2k.
> * crypto/rand: use defer to unlock mutex (thanks Anschel Schaffer-Cohen).
> * crypto/rsa: correct docstring for SignPKCS1v15.
> * crypto: add package, a common place to store identifiers for hash functions.
> * doc/codelab/wiki: update to work with template changes, add to run.bash.
> * doc/spec: clarify address operators.
> * ebnflint: exit with non-zero status on error.
> * encoding/base32: new package (thanks Miek Gieben).
> * encoding/line: make it an io.Reader too.
> * exec: use custom error for LookPath (thanks Gustavo Niemeyer).
> * fmt/doc: define width and precision for strings.
> * gc: clearer error for struct == struct,
>        fix send precedence,
>        handle invalid name in type switch,
>        special case code for single-op blocking and non-blocking selects.
> * go/scanner: fix build (adjust scanner EOF linecount).
> * gob: better debugging, commentary,
>        make nested interfaces work,
>        report an error when encoding a non-empty struct with no public fields.
> * godoc: full text index for whitelisted non-Go files,
>        show line numbers for non-go files (bug fix).
> * gofmt -r: match(...) arguments may be nil; add missing guards.
> * govet: add Panic to the list of functions.
> * http: add host patterns (thanks Jose Luis Vázquez González),
>        follow relative redirect in Get.
> * json: handle capital floating point exponent (1E100) (thanks Pieter
> Droogendijk).
> * ld: add -I option to set ELF interpreter,
>        more robust decoding of reflection type info in generating dwarf.
> * lib9: update to Unicode 6.0.0.
> * make.bash: stricter selinux test (don't complain unless it is enabled).
> * misc/vim: Import/Drop commands (thanks Gustavo Niemeyer),
>        set 'syntax sync' to a large value (thanks Yasuhiro Matsumoto).
> * net: fix race condition in test,
>        return cname in LookupHost.
> * netchan: avoid race condition in test,
>        fixed documentation for import (thanks Anschel Schaffer-Cohen).
> * os: add ETIMEDOUT (thanks Albert Strasheim).
> * runtime: generate Go defs for C types,
>        implementation of callback functions for windows (thanks Alex Brainman),
>        make Walk web browser example work (thanks Hector Chu),
>        make select fairer,
>        prefer fixed stack allocator over general memory allocator,
>        simpler heap map, memory allocation.
> * scanner: fix Position returned by Scan, Pos,
>        don't read ahead in Init.
> * suffixarray: use binary search for both ends of Lookup (thanks Eric Eisner).
> * syscall: add missing network interface constants (thanks Mikio Hara).
> * template: treat map keys as zero, not non-existent (thanks Roger Peppe).
> * time: allow cancelling of After events (thanks Roger Peppe),
>        support Solaris zoneinfo directory.
> * token/position: added SetLinesForContent.
> * unicode: update to unicode 6.0.0.
> * unsafe: add missing case to doc for Pointer.

> Apologies if we missed anyone in the list above. We appreciate all your help.

> To see a full list of changes between this and the previous release,
> after updating, run:
>  hg log -r release.2011-01-20:release.2011-02-01.1

> Enjoy.

> Andrew

On Tue, Feb 1, 2011 at 6:45 PM, Andrew Gerrand <a...@google.com> wrote:
> We've just tagged a new Go release, release.2011-02-01. As usual, you
> can update by running:
>  hg pull
>  hg update release

> This release includes significant changes to channel operations and minor
> changes to the log package. Your code will require modification if it uses
> channels in non-blocking communications or the log package's Exit functions.

> Non-blocking channel operations have been removed from the language.
> The equivalent operations have always been possible using a select statement
> with a default clause.  If a default clause is present in a select, that clause
> will execute (only) if no other is ready, which allows one to avoid blocking on
> a communication.

> For example, the old non-blocking send operation,

>        if ch <- v {
>                // sent
>        } else {
>                // not sent
>        }

> should be rewritten as,

>        select {
>        case ch <- v:
>                // sent
>        default:
>                // not sent
>        }

> Similarly, this receive,

>        v, ok := <-ch
>        if ok {
>                // received
>        } else {
>                // not received
>        }

> should be rewritten as,

>        select {
>        case v := <-ch:
>                // received
>        default:
>                // not received
>        }

> This change is a prelude to redefining the 'comma-ok' syntax for a receive.
> In a later release, a receive expression will return the received value and an
> optional boolean indicating whether the channel has been closed. These changes
> are being made in two stages to prevent this semantic change from silently
> breaking code that uses 'comma-ok' with receives.
> There are no plans to have a boolean expression form for sends.

> Sends to a closed channel will panic immediately. Previously, an unspecified
> number of sends would fail silently before causing a panic.

> The log package's Exit, Exitf, and Exitln functions have been renamed Fatal,
> Fatalf, and Fatalln respectively. This brings them in line with the naming of
> the testing package.

> The port to the "tiny" operating system has been removed. It is unmaintained
> and untested. It was a toy to show that Go can run on raw hardware and it
> served its purpose. The source code will of course remain in the repository
> history, so it could be brought back if needed later.

> This release also changes some of the internal structure of the memory
> allocator in preparation for other garbage collector changes.
> If you run into problems, please let us know.
> There is one known issue that we are aware of but have not debugged yet:
>        http://code.google.com/p/go/issues/detail?id=1464&.

> Other changes in this release:
> * 5l: document -F, force it on old ARMs (software floating point emulation)
> * 6g: fix registerization of temporaries (thanks Eoghan Sherry),
>        fix uint64(uintptr(unsafe.Pointer(&x))).
> * 6l: Relocate CMOV* instructions (thanks Gustavo Niemeyer),
>        windows/amd64 port (thanks Wei Guangjing).
> * 8l: add PE dynexport, emit DWARF in Windows PE, and
>        code generation fixes (thanks Wei Guangjing).
> * bufio: make Flush a no-op when the buffer is empty.
> * bytes: Add Buffer.ReadBytes, Buffer.ReadString (thanks Evan Shaw).
> * cc: mode to generate go-code for types and variables.
> * cgo: define CGO_CFLAGS and CGO_LDFLAGS in Go files (thanks Gustavo Niemeyer),
>        windows/386 port (thanks Wei Guangjing).
> * codereview: fix windows (thanks Hector Chu),
>        handle file patterns better,
>        more ASCII vs. Unicode nonsense.
> * crypto/dsa: add support for DSA.
> * crypto/openpgp: add s2k.
> * crypto/rand: use defer to unlock mutex (thanks Anschel Schaffer-Cohen).
> * crypto/rsa: correct docstring for SignPKCS1v15.
> * crypto: add package, a common place to store identifiers for hash functions.
> * doc/codelab/wiki: update to work with template changes, add to run.bash.
> * doc/spec: clarify address operators.
> * ebnflint: exit with non-zero status on error.
> * encoding/base32: new package (thanks Miek Gieben).
> * encoding/line: make it an io.Reader too.
> * exec: use custom error for LookPath (thanks Gustavo Niemeyer).
> * fmt/doc: define width and precision for strings.
> * gc: clearer error for struct == struct,
>        fix send precedence,
>        handle invalid name in type switch,
>        special case code for single-op blocking and non-blocking selects.
> * go/scanner: fix build (adjust scanner EOF linecount).
> * gob: better debugging, commentary,
>        make nested interfaces work,
>        report an error when encoding a non-empty struct with no public fields.
> * godoc: full text index for whitelisted non-Go files,
>        show line numbers for non-go files (bug fix).
> * gofmt -r: match(...) arguments may be nil; add missing guards.
> * govet: add Panic to the list of functions.
> * http: add host patterns (thanks Jose Luis Vázquez González),
>        follow relative redirect in Get.
> * json: handle capital floating point exponent (1E100) (thanks Pieter
> Droogendijk).
> * ld: add -I option to set ELF interpreter,
>        more robust decoding of reflection type info in generating dwarf.
> * lib9: update to Unicode 6.0.0.
> * make.bash: stricter selinux test (don't complain unless it is enabled).
> * misc/vim: Import/Drop commands (thanks Gustavo Niemeyer),
>        set 'syntax sync' to a large value (thanks Yasuhiro Matsumoto).
> * net: fix race condition in test,
>        return cname in LookupHost.
> * netchan: avoid race condition in test,
>        fixed documentation for import (thanks Anschel Schaffer-Cohen).
> * os: add ETIMEDOUT (thanks Albert Strasheim).
> * runtime: generate Go defs for C types,
>        implementation of callback functions for windows (thanks Alex Brainman),
>        make Walk web browser example work (thanks Hector Chu),
>        make select fairer,
>        prefer fixed stack allocator over general memory allocator,
>        simpler heap map, memory allocation.
> * scanner: fix Position returned by Scan, Pos,
>        don't read ahead in Init.
> * suffixarray: use binary search for both ends of Lookup (thanks Eric Eisner).
> * syscall: add missing network interface constants (thanks Mikio Hara).
> * template: treat map keys as zero, not non-existent (thanks Roger Peppe).
> * time: allow cancelling of After events (thanks Roger Peppe),
>        support Solaris zoneinfo directory.
> * token/position: added SetLinesForContent.
> * unicode: update to unicode 6.0.0.
> * unsafe: add missing case to doc for Pointer.

> Apologies if we missed anyone in the list above. We appreciate all your help.

> To see a full list of changes between this and the previous release,
> after updating, run:
>  hg log -r release.2011-01-20:release.2011-02-01.1

> Enjoy.

> Andrew

> * 8l: add PE dynexport, emit DWARF in Windows PE [...] (thanks Wei Guangjing).
> * cgo: [...]
>         windows/386 port (thanks Wei Guangjing).
> * runtime: [...]
>         implementation of callback functions for windows (thanks Alex Brainman),
>         make Walk web browser example work (thanks Hector Chu),

> and this:
>                _ = ch <- v

> changed to this, i think:

>                select {
>                case ch <- v:
>                 }

> should be rewritten as,

>        select {
>        case ch <- v:
>                // sent
>        default:
>                // not sent
>        }

> On Feb 2, 3:45 am, Andrew Gerrand <a...@google.com> wrote:
>> * 8l: add PE dynexport, emit DWARF in Windows PE [...] (thanks Wei Guangjing).
>> * cgo: [...]
>>         windows/386 port (thanks Wei Guangjing).
>> * runtime: [...]
>>         implementation of callback functions for windows (thanks Alex Brainman),
>>         make Walk web browser example work (thanks Hector Chu),

> Wow, as for Windows, that's MAJOR! :)
> Big thanks to Alex, Wei, Hector, and all other Win32 magicians! :)

> We've just tagged a new Go release, release.2011-02-01. As usual, you
> can update by running:
>  hg pull
>  hg update release

> This release includes significant changes to channel operations and minor
> changes to the log package. Your code will require modification if it uses
> channels in non-blocking communications or the log package's Exit functions.

> Non-blocking channel operations have been removed from the language.
> The equivalent operations have always been possible using a select statement
> with a default clause.  If a default clause is present in a select, that clause
> will execute (only) if no other is ready, which allows one to avoid blocking on
> a communication.

> For example, the old non-blocking send operation,

>         if ch <- v {
>                 // sent
>         } else {
>                 // not sent
>         }

> should be rewritten as,

>         select {
>         case ch <- v:
>                 // sent
>         default:
>                 // not sent
>         }

> Similarly, this receive,

>         v, ok := <-ch
>         if ok {
>                 // received
>         } else {
>                 // not received
>         }

> should be rewritten as,

>         select {
>         case v := <-ch:
>                 // received
>         default:
>                 // not received
>         }

> This change is a prelude to redefining the 'comma-ok' syntax for a receive.
> In a later release, a receive expression will return the received value and an
> optional boolean indicating whether the channel has been closed. These changes
> are being made in two stages to prevent this semantic change from silently
> breaking code that uses 'comma-ok' with receives.
> There are no plans to have a boolean expression form for sends.

> Sends to a closed channel will panic immediately. Previously, an unspecified
> number of sends would fail silently before causing a panic.

> The log package's Exit, Exitf, and Exitln functions have been renamed Fatal,
> Fatalf, and Fatalln respectively. This brings them in line with the naming of
> the testing package.

> The port to the "tiny" operating system has been removed. It is unmaintained
> and untested. It was a toy to show that Go can run on raw hardware and it
> served its purpose. The source code will of course remain in the repository
> history, so it could be brought back if needed later.

> This release also changes some of the internal structure of the memory
> allocator in preparation for other garbage collector changes.
> If you run into problems, please let us know.
> There is one known issue that we are aware of but have not debugged yet:
>        http://code.google.com/p/go/issues/detail?id=1464&.

> Other changes in this release:
> * 5l: document -F, force it on old ARMs (software floating point emulation)
> * 6g: fix registerization of temporaries (thanks Eoghan Sherry),
>         fix uint64(uintptr(unsafe.Pointer(&x))).
> * 6l: Relocate CMOV* instructions (thanks Gustavo Niemeyer),
>         windows/amd64 port (thanks Wei Guangjing).
> * 8l: add PE dynexport, emit DWARF in Windows PE, and
>         code generation fixes (thanks Wei Guangjing).
> * bufio: make Flush a no-op when the buffer is empty.
> * bytes: Add Buffer.ReadBytes, Buffer.ReadString (thanks Evan Shaw).
> * cc: mode to generate go-code for types and variables.
> * cgo: define CGO_CFLAGS and CGO_LDFLAGS in Go files (thanks Gustavo Niemeyer),
>         windows/386 port (thanks Wei Guangjing).
> * codereview: fix windows (thanks Hector Chu),
>         handle file patterns better,
>         more ASCII vs. Unicode nonsense.
> * crypto/dsa: add support for DSA.
> * crypto/openpgp: add s2k.
> * crypto/rand: use defer to unlock mutex (thanks Anschel Schaffer-Cohen).
> * crypto/rsa: correct docstring for SignPKCS1v15.
> * crypto: add package, a common place to store identifiers for hash functions.
> * doc/codelab/wiki: update to work with template changes, add to run.bash.
> * doc/spec: clarify address operators.
> * ebnflint: exit with non-zero status on error.
> * encoding/base32: new package (thanks Miek Gieben).

> * encoding/line: make it an io.Reader too.
> * exec: use custom error for LookPath (thanks Gustavo Niemeyer).
> * fmt/doc: define width and precision for strings.
> * gc: clearer error for struct == struct,
>         fix send precedence,
>         handle invalid name in type switch,
>         special case code for single-op blocking and non-blocking selects.
> * go/scanner: fix build (adjust scanner EOF linecount).
> * gob: better debugging, commentary,
>         make nested interfaces work,
>         report an error when encoding a non-empty struct with no public fields.
> * godoc: full text index for whitelisted non-Go files,
>         show line numbers for non-go files (bug fix).
> * gofmt -r: match(...) arguments may be nil; add missing guards.
> * govet: add Panic to the list of functions.
> * http: add host patterns (thanks Jose Luis Vázquez González),
>         follow relative redirect in Get.
> * json: handle capital floating point exponent (1E100) (thanks Pieter
> Droogendijk).
> * ld: add -I option to set ELF interpreter,
>         more robust decoding of reflection type info in generating dwarf.
> * lib9: update to Unicode 6.0.0.
> * make.bash: stricter selinux test (don't complain unless it is enabled).
> * misc/vim: Import/Drop commands (thanks Gustavo Niemeyer),
>         set 'syntax sync' to a large value (thanks Yasuhiro Matsumoto).
> * net: fix race condition in test,
>         return cname in LookupHost.
> * netchan: avoid race condition in test,
>         fixed documentation for import (thanks Anschel Schaffer-Cohen).
> * os: add ETIMEDOUT (thanks Albert Strasheim).
> * runtime: generate Go defs for C types,
>         implementation of callback functions for windows (thanks Alex Brainman),
>         make Walk web browser example work (thanks Hector Chu),
>         make select fairer,
>         prefer fixed stack allocator over general memory allocator,
>         simpler heap map, memory allocation.
> * scanner: fix Position returned by Scan, Pos,
>         don't read ahead in Init.
> * suffixarray: use binary search for both ends of Lookup (thanks Eric Eisner).
> * syscall: add missing network interface constants (thanks Mikio Hara).
> * template: treat map keys as zero, not non-existent (thanks Roger Peppe).
> * time: allow cancelling of After events (thanks Roger Peppe),
>         support Solaris zoneinfo directory.
> * token/position: added SetLinesForContent.
> * unicode: update to unicode 6.0.0.
> * unsafe: add missing case to doc for Pointer.

> Apologies if we missed anyone in the list above. We appreciate all your help.

> To see a full list of changes between this and the previous release,
> after updating, run:
>  hg log -r release.2011-01-20:release.2011-02-01.1

> Enjoy.

> Andrew

> There has been some discussion if base32 warrants an inclusion as a
> core package. I recently discovered geohash
> http://en.wikipedia.org/wiki/Geohash
> where base32 just fits fine; (Nodding towards Gustavo ;) )

> This change is a prelude to redefining the 'comma-ok' syntax for a receive.
> In a later release, a receive expression will return the received value and an
> optional boolean indicating whether the channel has been closed. These changes
> are being made in two stages to prevent this semantic change from silently
> breaking code that uses 'comma-ok' with receives.
> There are no plans to have a boolean expression form for sends.

> Sends to a closed channel will panic immediately. Previously, an unspecified
> number of sends would fail silently before causing a panic.

> I am a little confused by this. The 'close' operation is *not*
> required for construction of general-purpose concurrent programs (and
> Go has a garbage collector). Why not remove it completely?

> On 3 February 2011 23:36, ⚛ <0xe2.0x9a.0...@gmail.com> wrote:

> > I am a little confused by this. The 'close' operation is *not*
> > required for construction of general-purpose concurrent programs (and
> > Go has a garbage collector). Why not remove it completely?

> Close is a convenience that simplifies sending a finite set of values
> down a channel and ranging over it at the receiving end.

> The upcoming changes make it possible to detect a channel is closed
> only at the receiving end. This should allow us to keep the
> convenience of close while removing tricky the handling of race
> conditions and confusion created by its misuse.

> Andrew

> Without locks, it is impossible to implement codes such as:

> if !closed(ch) { some-actions; close(ch) }

> because the access to the channel is not atomic. You have to do:

> On Feb 3, 1:52 pm, Andrew Gerrand <a...@golang.org> wrote:
>> On 3 February 2011 23:36, ⚛ <0xe2.0x9a.0...@gmail.com> wrote:

>> > I am a little confused by this. The 'close' operation is *not*
>> > required for construction of general-purpose concurrent programs (and
>> > Go has a garbage collector). Why not remove it completely?

>> Close is a convenience that simplifies sending a finite set of values
>> down a channel and ranging over it at the receiving end.

> Yes. But supposing closing a channel is removed from the language, the
> "for ... range channel" construct could still be used. The difference
> would be that the programmer would have to explicitly break from the
> loop when the last element is detected.

>> The upcoming changes make it possible to detect a channel is closed
>> only at the receiving end. This should allow us to keep the
>> convenience of close while removing tricky the handling of race
>> conditions and confusion created by its misuse.

>> Andrew

> In my opinion, the proposed future addition (= a receive expression
> will return the received value and an optional boolean indicating
> whether the channel has been closed) will leave the tricky race
> conditions and confusions due to misuse at approximately the same
> level as they are right now.

On Thu, Feb 3, 2011 at 6:52 AM, Andrew Gerrand <a...@golang.org> wrote:
> Close is a convenience that simplifies sending a finite set of values
> down a channel and ranging over it at the receiving end.

> Because nil is a fine value to send on a channel.  Why take it away?
> It seems less magic to me to have a separate close() operator that,
> being explicit rather than implicit, is likelier to have heavier
> semantics, as indeed it does.

> -rob

> The difference would be that range would stop iterating upon receiving a
> nil.  It would be analogous to fmt.Printf stopping at a null character.  I

> > The difference would be that range would stop iterating upon receiving a
> > nil.  It would be analogous to fmt.Printf stopping at a null character.
>  I

> That's an excellent analogy, actually.  Have you noticed it doesn't? :-)

> --
> Gustavo Niemeyer
> http://niemeyer.net
> http://niemeyer.net/blog
> http://niemeyer.net/twitter

> Yeah yeah... nor am I saying it should.  Just an analogy.

> Thanks.
> Ryanne

> --www.ryannedolan.info

> On Thu, Feb 3, 2011 at 12:09 PM, Gustavo Niemeyer <gust...@niemeyer.net>wrote:

> > > The difference would be that range would stop iterating upon receiving a
> > > nil.  It would be analogous to fmt.Printf stopping at a null character.
> >  I

> > That's an excellent analogy, actually.  Have you noticed it doesn't? :-)

> > --
> > Gustavo Niemeyer
> >http://niemeyer.net
> >http://niemeyer.net/blog
> >http://niemeyer.net/twitter

> Non-blocking channel operations have been removed from the language.

>> Non-blocking channel operations have been removed from the language.

> Maybe it is not related. In "reflect" pkg, there are methods
> ChanValue.trySend()/TryRecv(). Will these methods remain in future?

> Because nil is a fine value to send on a channel.  Why take it away?
> It seems less magic to me to have a separate close() operator that,
> being explicit rather than implicit, is likelier to have heavier
> semantics, as indeed it does.

> -rob

> Shouldn't close() be removed and handled automatically due to the same
> reasons free() was removed and is being handled automatically?

> close() on a channel is analogous to free() on a memory location. Go
> does not have free(), one reason is that it is error prone and complex
> when sharing memory across multiple goroutines. Applying the same
> reasoning to channels: Go should not have close().

> Shouldn't close() be removed and handled automatically due to the same
> reasons free() was removed and is being handled automatically?

> If we can very easily forget about free() when dealing with memory,
> *what* is preventing us from forgetting about close()?