The latest Go release, version 1.3, arrives six months after 1.2, and contains no language changes. It focuses primarily on implementation work, providing precise garbage collection, a major refactoring of the compiler tool chain that results in faster builds, especially for large projects, significant performance improvements across the board, and support for Solaris and Google's Native Client architecture (NaCl). It also has an important refinement to the memory model regarding synchronization. As always, Go 1.3 keeps the promise of compatibility, and almost everything will continue to compile and run without change when moved to 1.3.
TODO
TODO
Microsoft stopped supporting Windows 2000 in 2010. Since it has implementation difficulties regarding exception handling (signals in Unix terminology), as of Go 1.3 it is not supported by Go either.
The Go 1.3 memory model adds a new rule concerning sending and receiving on buffered channels, to make explicit that a buffered channel can be used as a simple semaphore, using a send into the channel to acquire and a receive from the channel to release. This is not a language change, just a clarification about an expected property of communication.
Go 1.3 has changed the implementation of goroutine stacks away from the old, "segmented" model to a contiguous model. When a goroutine needs more stack than is available, its stack is transferred to a larger single block of memory. The overhead of this transfer operation amortizes well and eliminates the old "hot spot" problem when a calculation repeatedly steps across a segment boundary. Details including performance numbers are in this design document.
Go 1.2 increased the minimum stack size to 8 kilobytes; with the new stack model, it has been put back to 4 kilobytes.
precision (TODO what to say) liveness (TODO what to say)
As part of the general overhaul to
the Go linker, the compilers and linkers have been refactored.
The linker is still a C program, but now the instruction selection phase that
was part of the linker has been moved to the compiler through the creation of a new
library called liblink.
By doing instruction selection only once, when the package is first compiled,
this can speed up compilation of large projects significantly.
Updating: Although this is a major internal change, it should have no effect on programs.
GCC release 4.9 will contain the Go 1.2 (not 1.3) version of gccgo. The release schedules for the GCC and Go projects do not coincide, which means that 1.3 will be available in the development branch but that the next GCC release, 4.10, will likely have the Go 1.4 version of gccgo.
TODO cmd/go, go/build: support .m files (CL 60590044) cmd/go: add -exec to 'go run' and 'go test' (CL 68580043) cmd/go: cover -atomic for -race (CL 76370043)
The program misc/benchcmp that compares
performance across benchmarking runs has been rewritten.
Once a shell and awk script in the main repository, it is now a Go program in the go.tools repo.
Documentation is here.
misc/dist has been
moved and renamed; it now lives in misc/makerelease, still in the main repository.
The performance of Go binaries for this release has improved in many cases due to changes in the runtime and garbage collection, plus some changes to libraries. Significant instances include:
regexp
is now significantly faster for certain simple expressions due to the implemenation of
a second, one-pass execution engine. The choice of which engine to use is automatic;
the details are hidden from the user.
Also, the runtime now includes in stack dumps how long a goroutine has been blocked, which can be useful information when debugging deadlocks or performance issues.
No new packages appear in the core libraries in Go 1.3.
There is an important new type added to the standard library: sync.Pool.
It provides an efficient mechanism for implementing certain types of caches whose memory
can be reclaimed automatically by the system.
TODO: crypto/tls: ServerName or InsecureSkipVerify (CL 67010043) possible breaking change
The following list summarizes a number of minor changes to the library, mostly additions. See the relevant package documentation for more information about each change.
Pow,
now specifies the behavior when the first argument is zero. It was undefined before.
The details are in the documentation for the function.
fmt package now define %F
as a synonym for %f when printing floating-point values.
net/http package now exposes the
the properties of a TLS connection used to make a client request in the new
Response.TLS field.
net/http package now
allows setting an optional server error logger
with Server.ErrorLog.
The default is still that all errors go to stderr.
os/exec package now implements
what the documentation has always said with regard to relative paths for the binary.
In particular, it only calls LookPath
when the binary's file name contains no path separators.
CanBackquote
function in the strconv package
now considers the DEL character, U+007F, to be
non-printing.
testing package now
diagnoses tests that call panic(nil), which are almost always erroneous.
unicode package and associated
support throughout the system has been upgraded from
Unicode 6.2.0 to Unicode 6.3.0.