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1311 lines
47 KiB
1311 lines
47 KiB
<!--{
|
|
"Title": "Go 1.5 Release Notes",
|
|
"Path": "/doc/go1.5",
|
|
"Template": true
|
|
}-->
|
|
|
|
|
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<h2 id="introduction">Introduction to Go 1.5</h2>
|
|
|
|
<p>
|
|
The latest Go release, version 1.5,
|
|
is a significant release, including major architectural changes to the implementation.
|
|
Despite that, we expect almost all Go programs to continue to compile and run as before,
|
|
because the release still maintains the Go 1 <a href="/doc/go1compat.html">promise
|
|
of compatibility</a>.
|
|
</p>
|
|
|
|
<p>
|
|
The biggest developments in the implementation are:
|
|
</p>
|
|
|
|
<ul>
|
|
|
|
<li>
|
|
The compiler and runtime are now written entirely in Go (with a little assembler).
|
|
C is no longer involved in the implementation, and so the C compiler that was
|
|
once necessary for building the distribution is gone.
|
|
</li>
|
|
|
|
<li>
|
|
The garbage collector is now <a href="https://golang.org/s/go14gc">concurrent</a> and provides dramatically lower
|
|
pause times by running, when possible, in parallel with other goroutines.
|
|
</li>
|
|
|
|
<li>
|
|
By default, Go programs run with <code>GOMAXPROCS</code> set to the
|
|
number of cores available; in prior releases it defaulted to 1.
|
|
</li>
|
|
|
|
<li>
|
|
Support for <a href="https://golang.org/s/go14internal">internal packages</a>
|
|
is now provided for all repositories, not just the Go core.
|
|
</li>
|
|
|
|
<li>
|
|
The <code>go</code> command now provides <a href="https://golang.org/s/go15vendor">experimental
|
|
support</a> for "vendoring" external dependencies.
|
|
</li>
|
|
|
|
<li>
|
|
A new <code>go tool trace</code> command supports fine-grained
|
|
tracing of program execution.
|
|
</li>
|
|
|
|
<li>
|
|
A new <code>go doc</code> command (distinct from <code>godoc</code>)
|
|
is customized for command-line use.
|
|
</li>
|
|
|
|
</ul>
|
|
|
|
<p>
|
|
These and a number of other changes to the implementation and tools
|
|
are discussed below.
|
|
</p>
|
|
|
|
<p>
|
|
The release also contains one small language change involving map literals.
|
|
</p>
|
|
|
|
<p>
|
|
Finally, the timing of the <a href="https://golang.org/s/releasesched">release</a>
|
|
strays from the usual six-month interval,
|
|
both to provide more time to prepare this major release and to shift the schedule thereafter to
|
|
time the release dates more conveniently.
|
|
</p>
|
|
|
|
<h2 id="language">Changes to the language</h2>
|
|
|
|
<h3 id="map_literals">Map literals</h3>
|
|
|
|
<p>
|
|
Due to an oversight, the rule that allowed the element type to be elided from slice literals was not
|
|
applied to map keys.
|
|
This has been <a href="/cl/2591">corrected</a> in Go 1.5.
|
|
An example will make this clear.
|
|
As of Go 1.5, this map literal,
|
|
</p>
|
|
|
|
<pre>
|
|
m := map[Point]string{
|
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Point{29.935523, 52.891566}: "Persepolis",
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Point{-25.352594, 131.034361}: "Uluru",
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Point{37.422455, -122.084306}: "Googleplex",
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|
}
|
|
</pre>
|
|
|
|
<p>
|
|
may be written as follows, without the <code>Point</code> type listed explicitly:
|
|
</p>
|
|
|
|
<pre>
|
|
m := map[Point]string{
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{29.935523, 52.891566}: "Persepolis",
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{-25.352594, 131.034361}: "Uluru",
|
|
{37.422455, -122.084306}: "Googleplex",
|
|
}
|
|
</pre>
|
|
|
|
<h2 id="implementation">The Implementation</h2>
|
|
|
|
<h3 id="c">No more C</h3>
|
|
|
|
<p>
|
|
The compiler and runtime are now implemented in Go and assembler, without C.
|
|
The only C source left in the tree is related to testing or to <code>cgo</code>.
|
|
There was a C compiler in the tree in 1.4 and earlier.
|
|
It was used to build the runtime; a custom compiler was necessary in part to
|
|
guarantee the C code would work with the stack management of goroutines.
|
|
Since the runtime is in Go now, there is no need for this C compiler and it is gone.
|
|
Details of the process to eliminate C are discussed <a href="https://golang.org/s/go13compiler">elsewhere</a>.
|
|
</p>
|
|
|
|
<p>
|
|
The conversion from C was done with the help of custom tools created for the job.
|
|
Most important, the compiler was actually moved by automatic translation of
|
|
the C code into Go.
|
|
It is in effect the same program in a different language.
|
|
It is not a new implementation
|
|
of the compiler so we expect the process will not have introduced new compiler
|
|
bugs.
|
|
An overview of this process is available in the slides for
|
|
<a href="https://talks.golang.org/2015/gogo.slide">this presentation</a>.
|
|
</p>
|
|
|
|
<h3 id="compiler_and_tools">Compiler and tools</h3>
|
|
|
|
<p>
|
|
Independent of but encouraged by the move to Go, the names of the tools have changed.
|
|
The old names <code>6g</code>, <code>8g</code> and so on are gone; instead there
|
|
is just one binary, accessible as <code>go</code> <code>tool</code> <code>compile</code>,
|
|
that compiles Go source into binaries suitable for the architecture and operating system
|
|
specified by <code>$GOARCH</code> and <code>$GOOS</code>.
|
|
Similarly, there is now one linker (<code>go</code> <code>tool</code> <code>link</code>)
|
|
and one assembler (<code>go</code> <code>tool</code> <code>asm</code>).
|
|
The linker was translated automatically from the old C implementation,
|
|
but the assembler is a new native Go implementation discussed
|
|
in more detail below.
|
|
</p>
|
|
|
|
<p>
|
|
Similar to the drop of the names <code>6g</code>, <code>8g</code>, and so on,
|
|
the output of the compiler and assembler are now given a plain <code>.o</code> suffix
|
|
rather than <code>.8</code>, <code>.6</code>, etc.
|
|
</p>
|
|
|
|
|
|
<h3 id="gc">Garbage collector</h3>
|
|
|
|
<p>
|
|
The garbage collector has been re-engineered for 1.5 as part of the development
|
|
outlined in the <a href="https://golang.org/s/go14gc">design document</a>.
|
|
Expected latencies are much lower than with the collector
|
|
in prior releases, through a combination of advanced algorithms,
|
|
better <a href="https://golang.org/s/go15gcpacing">scheduling</a> of the collector,
|
|
and running more of the collection in parallel with the user program.
|
|
The "stop the world" phase of the collector
|
|
will almost always be under 10 milliseconds and usually much less.
|
|
</p>
|
|
|
|
<p>
|
|
For systems that benefit from low latency, such as user-responsive web sites,
|
|
the drop in expected latency with the new collector may be important.
|
|
</p>
|
|
|
|
<p>
|
|
Details of the new collector were presented in a
|
|
<a href="https://talks.golang.org/2015/go-gc.pdf">talk</a> at GopherCon 2015.
|
|
</p>
|
|
|
|
<h3 id="runtime">Runtime</h3>
|
|
|
|
<p>
|
|
In Go 1.5, the order in which goroutines are scheduled has been changed.
|
|
The properties of the scheduler were never defined by the language,
|
|
but programs that depend on the scheduling order may be broken
|
|
by this change.
|
|
We have seen a few (erroneous) programs affected by this change.
|
|
If you have programs that implicitly depend on the scheduling
|
|
order, you will need to update them.
|
|
</p>
|
|
|
|
<p>
|
|
Another potentially breaking change is that the runtime now
|
|
sets the default number of threads to run simultaneously,
|
|
defined by <code>GOMAXPROCS</code>, to the number
|
|
of cores available on the CPU.
|
|
In prior releases the default was 1.
|
|
Programs that do not expect to run with multiple cores may
|
|
break inadvertently.
|
|
They can be updated by removing the restriction or by setting
|
|
<code>GOMAXPROCS</code> explicitly.
|
|
For a more detailed discussion of this change, see
|
|
the <a href="https://golang.org/s/go15gomaxprocs">design document</a>.
|
|
</p>
|
|
|
|
<h3 id="build">Build</h3>
|
|
|
|
<p>
|
|
Now that the Go compiler and runtime are implemented in Go, a Go compiler
|
|
must be available to compile the distribution from source.
|
|
Thus, to build the Go core, a working Go distribution must already be in place.
|
|
(Go programmers who do not work on the core are unaffected by this change.)
|
|
Any Go 1.4 or later distribution (including <code>gccgo</code>) will serve.
|
|
For details, see the <a href="https://golang.org/s/go15bootstrap">design document</a>.
|
|
</p>
|
|
|
|
<h2 id="ports">Ports</h2>
|
|
|
|
<p>
|
|
Due mostly to the industry's move away from the 32-bit x86 architecture,
|
|
the set of binary downloads provided is reduced in 1.5.
|
|
A distribution for the OS X operating system is provided only for the
|
|
<code>amd64</code> architecture, not <code>386</code>.
|
|
Similarly, the ports for Snow Leopard (Apple OS X 10.6) still work but are no
|
|
longer released as a download or maintained since Apple no longer maintains that version
|
|
of the operating system.
|
|
Also, the <code>dragonfly/386</code> port is no longer supported at all
|
|
because DragonflyBSD itself no longer supports the 32-bit 386 architecture.
|
|
</p>
|
|
|
|
<p>
|
|
There are however several new ports available to be built from source.
|
|
These include <code>darwin/arm</code> and <code>darwin/arm64</code>.
|
|
The new port <code>linux/arm64</code> is mostly in place, but <code>cgo</code>
|
|
is only supported using external linking.
|
|
</p>
|
|
|
|
<p>
|
|
Also available as experiments are <code>ppc64</code>
|
|
and <code>ppc64le</code> (64-bit PowerPC, big- and little-endian).
|
|
Both these ports support <code>cgo</code> but
|
|
only with internal linking.
|
|
</p>
|
|
|
|
<p>
|
|
On FreeBSD, Go 1.5 requires FreeBSD 8-STABLE+ because of its new use of the <code>SYSCALL</code> instruction.
|
|
</p>
|
|
|
|
<p>
|
|
On NaCl, Go 1.5 requires SDK version pepper-41. Later pepper versions are not
|
|
compatible due to the removal of the sRPC subsystem from the NaCl runtime.
|
|
</p>
|
|
|
|
<p>
|
|
On Darwin, the use of the system X.509 certificate interface can be disabled
|
|
with the <code>ios</code> build tag.
|
|
</p>
|
|
|
|
<p>
|
|
The Solaris port now has full support for cgo and the packages
|
|
<a href="/pkg/net/"><code>net</code></a> and
|
|
<a href="/pkg/crypto/x509/"><code>crypto/x509</code></a>,
|
|
as well as a number of other fixes and improvements.
|
|
</p>
|
|
|
|
<h2 id="tools">Tools</h2>
|
|
|
|
<h3 id="translate">Translating</h3>
|
|
|
|
<p>
|
|
As part of the process to eliminate C from the tree, the compiler and
|
|
linker were translated from C to Go.
|
|
It was a genuine (machine assisted) translation, so the new programs are essentially
|
|
the old programs translated rather than new ones with new bugs.
|
|
We are confident the translation process has introduced few if any new bugs,
|
|
and in fact uncovered a number of previously unknown bugs, now fixed.
|
|
</p>
|
|
|
|
<p>
|
|
The assembler is a new program, however; it is described below.
|
|
</p>
|
|
|
|
<h3 id="rename">Renaming</h3>
|
|
|
|
<p>
|
|
The suites of programs that were the compilers (<code>6g</code>, <code>8g</code>, etc.),
|
|
the assemblers (<code>6a</code>, <code>8a</code>, etc.),
|
|
and the linkers (<code>6l</code>, <code>8l</code>, etc.)
|
|
have each been consolidated into a single tool that is configured
|
|
by the environment variables <code>GOOS</code> and <code>GOARCH</code>.
|
|
The old names are gone; the new tools are available through the <code>go</code> <code>tool</code>
|
|
mechanism as <code>go tool compile</code>,
|
|
<code>go tool asm</code>,
|
|
<code>and go tool link</code>.
|
|
Also, the file suffixes <code>.6</code>, <code>.8</code>, etc. for the
|
|
intermediate object files are also gone; now they are just plain <code>.o</code> files.
|
|
</p>
|
|
|
|
<p>
|
|
For example, to build and link a program on amd64 for Darwin
|
|
using the tools directly, rather than through <code>go build</code>,
|
|
one would run:
|
|
</p>
|
|
|
|
<pre>
|
|
$ export GOOS=darwin GOARCH=amd64
|
|
$ go tool compile program.go
|
|
$ go tool link program.o
|
|
</pre>
|
|
|
|
<h3 id="moving">Moving</h3>
|
|
|
|
<p>
|
|
Because the <a href="/pkg/go/types/"><code>go/types</code></a> package
|
|
has now moved into the main repository (see below),
|
|
the <a href="/cmd/vet"><code>vet</code></a> and
|
|
<a href="/cmd/cover"><code>cover</code></a>
|
|
tools have also been moved.
|
|
They are no longer maintained in the external <code>golang.org/x/tools</code> repository,
|
|
although (deprecated) source still resides there for compatibility with old releases.
|
|
</p>
|
|
|
|
<h3 id="compiler">Compiler</h3>
|
|
|
|
<p>
|
|
As described above, the compiler in Go 1.5 is a single Go program,
|
|
translated from the old C source, that replaces <code>6g</code>, <code>8g</code>,
|
|
and so on.
|
|
Its target is configured by the environment variables <code>GOOS</code> and <code>GOARCH</code>.
|
|
</p>
|
|
|
|
<p>
|
|
The 1.5 compiler is mostly equivalent to the old,
|
|
but some internal details have changed.
|
|
One significant change is that evaluation of constants now uses
|
|
the <a href="/pkg/math/big/"><code>math/big</code></a> package
|
|
rather than a custom (and less well tested) implementation of high precision
|
|
arithmetic.
|
|
We do not expect this to affect the results.
|
|
</p>
|
|
|
|
<p>
|
|
For the amd64 architecture only, the compiler has a new option, <code>-dynlink</code>,
|
|
that assists dynamic linking by supporting references to Go symbols
|
|
defined in external shared libraries.
|
|
</p>
|
|
|
|
<h3 id="assembler">Assembler</h3>
|
|
|
|
<p>
|
|
Like the compiler and linker, the assembler in Go 1.5 is a single program
|
|
that replaces the suite of assemblers (<code>6a</code>,
|
|
<code>8a</code>, etc.) and the environment variables
|
|
<code>GOARCH</code> and <code>GOOS</code>
|
|
configure the architecture and operating system.
|
|
Unlike the other programs, the assembler is a wholly new program
|
|
written in Go.
|
|
</p>
|
|
|
|
<p>
|
|
The new assembler is very nearly compatible with the previous
|
|
ones, but there are a few changes that may affect some
|
|
assembler source files.
|
|
See the updated <a href="/doc/asm">assembler guide</a>
|
|
for more specific information about these changes. In summary:
|
|
|
|
</p>
|
|
|
|
<p>
|
|
First, the expression evaluation used for constants is a little
|
|
different.
|
|
It now uses unsigned 64-bit arithmetic and the precedence
|
|
of operators (<code>+</code>, <code>-</code>, <code><<</code>, etc.)
|
|
comes from Go, not C.
|
|
We expect these changes to affect very few programs but
|
|
manual verification may be required.
|
|
</p>
|
|
|
|
<p>
|
|
Perhaps more important is that on machines where
|
|
<code>SP</code> or <code>PC</code> is only an alias
|
|
for a numbered register,
|
|
such as <code>R13</code> for the stack pointer and
|
|
<code>R15</code> for the hardware program counter
|
|
on ARM,
|
|
a reference to such a register that does not include a symbol
|
|
is now illegal.
|
|
For example, <code>SP</code> and <code>4(SP)</code> are
|
|
illegal but <code>sym+4(SP)</code> is fine.
|
|
On such machines, to refer to the hardware register use its
|
|
true <code>R</code> name.
|
|
</p>
|
|
|
|
<p>
|
|
One minor change is that some of the old assemblers
|
|
permitted the notation
|
|
</p>
|
|
|
|
<pre>
|
|
constant=value
|
|
</pre>
|
|
|
|
<p>
|
|
to define a named constant.
|
|
Since this is always possible to do with the traditional
|
|
C-like <code>#define</code> notation, which is still
|
|
supported (the assembler includes an implementation
|
|
of a simplified C preprocessor), the feature was removed.
|
|
</p>
|
|
|
|
<h3 id="link">Linker</h3>
|
|
|
|
<p>
|
|
The linker in Go 1.5 is now one Go program,
|
|
that replaces <code>6l</code>, <code>8l</code>, etc.
|
|
Its operating system and instruction set are specified
|
|
by the environment variables <code>GOOS</code> and <code>GOARCH</code>.
|
|
</p>
|
|
|
|
<p>
|
|
There are several other changes.
|
|
The most significant is the addition of a <code>-buildmode</code> option that
|
|
expands the style of linking; it now supports
|
|
situations such as building shared libraries and allowing other languages
|
|
to call into Go libraries.
|
|
Some of these were outlined in a <a href="https://golang.org/s/execmodes">design document</a>.
|
|
For a list of the available build modes and their use, run
|
|
</p>
|
|
|
|
<pre>
|
|
$ go help buildmode
|
|
</pre>
|
|
|
|
<p>
|
|
Another minor change is that the linker no longer records build time stamps in
|
|
the header of Windows executables.
|
|
Also, although this may be fixed, Windows cgo executables are missing some
|
|
DWARF information.
|
|
</p>
|
|
|
|
<p>
|
|
Finally, the <code>-X</code> flag, which takes two arguments,
|
|
as in
|
|
</p>
|
|
|
|
<pre>
|
|
-X importpath.name value
|
|
</pre>
|
|
|
|
<p>
|
|
now also accepts a more common Go flag style with a single argument
|
|
that is itself a <code>name=value</code> pair:
|
|
</p>
|
|
|
|
<pre>
|
|
-X importpath.name=value
|
|
</pre>
|
|
|
|
<p>
|
|
Although the old syntax still works, it is recommended that uses of this
|
|
flag in scripts and the like be updated to the new form.
|
|
</p>
|
|
|
|
<h3 id="go_command">Go command</h3>
|
|
|
|
<p>
|
|
The <a href="/cmd/go"><code>go</code></a> command's basic operation
|
|
is unchanged, but there are a number of changes worth noting.
|
|
</p>
|
|
|
|
<p>
|
|
The previous release introduced the idea of a directory internal to a package
|
|
being unimportable through the <code>go</code> command.
|
|
In 1.4, it was tested with the introduction of some internal elements
|
|
in the core repository.
|
|
As suggested in the <a href="https://golang.org/s/go14internal">design document</a>,
|
|
that change is now being made available to all repositories.
|
|
The rules are explained in the design document, but in summary any
|
|
package in or under a directory named <code>internal</code> may
|
|
be imported by packages rooted in the same subtree.
|
|
Existing packages with directory elements named <code>internal</code> may be
|
|
inadvertently broken by this change, which was why it was advertised
|
|
in the last release.
|
|
</p>
|
|
|
|
<p>
|
|
Another change in how packages are handled is the experimental
|
|
addition of support for "vendoring".
|
|
For details, see the documentation for the <a href="/cmd/go/#hdr-Vendor_Directories"><code>go</code> command</a>
|
|
and the <a href="https://golang.org/s/go15vendor">design document</a>.
|
|
</p>
|
|
|
|
<p>
|
|
There have also been several minor changes.
|
|
Read the <a href="/cmd/go">documentation</a> for full details.
|
|
</p>
|
|
|
|
<ul>
|
|
|
|
<li>
|
|
SWIG support has been updated such that
|
|
<code>.swig</code> and <code>.swigcxx</code>
|
|
now require SWIG 3.0.6 or later.
|
|
</li>
|
|
|
|
<li>
|
|
The <code>install</code> subcommand now removes the
|
|
binary created by the <code>build</code> subcommand
|
|
in the source directory, if present,
|
|
to avoid problems having two binaries present in the tree.
|
|
</li>
|
|
|
|
<li>
|
|
The <code>std</code> (standard library) wildcard package name
|
|
now excludes commands.
|
|
A new <code>cmd</code> wildcard covers the commands.
|
|
</li>
|
|
|
|
<li>
|
|
A new <code>-asmflags</code> build option
|
|
sets flags to pass to the assembler.
|
|
However,
|
|
the <code>-ccflags</code> build option has been dropped;
|
|
it was specific to the old, now deleted C compiler .
|
|
</li>
|
|
|
|
<li>
|
|
A new <code>-buildmode</code> build option
|
|
sets the build mode, described above.
|
|
</li>
|
|
|
|
<li>
|
|
A new <code>-pkgdir</code> build option
|
|
sets the location of installed package archives,
|
|
to help isolate custom builds.
|
|
</li>
|
|
|
|
<li>
|
|
A new <code>-toolexec</code> build option
|
|
allows substitution of a different command to invoke
|
|
the compiler and so on.
|
|
This acts as a custom replacement for <code>go tool</code>.
|
|
</li>
|
|
|
|
<li>
|
|
The <code>test</code> subcommand now has a <code>-count</code>
|
|
flag to specify how many times to run each test and benchmark.
|
|
The <a href="/pkg/testing/"><code>testing</code></a> package
|
|
does the work here, through the <code>-test.count</code> flag.
|
|
</li>
|
|
|
|
<li>
|
|
The <code>generate</code> subcommand has a couple of new features.
|
|
The <code>-run</code> option specifies a regular expression to select which directives
|
|
to execute; this was proposed but never implemented in 1.4.
|
|
The executing pattern now has access to two new environment variables:
|
|
<code>$GOLINE</code> returns the source line number of the directive
|
|
and <code>$DOLLAR</code> expands to a dollar sign.
|
|
</li>
|
|
|
|
<li>
|
|
The <code>get</code> subcommand now has a <code>-insecure</code>
|
|
flag that must be enabled if fetching from an insecure repository, one that
|
|
does not encrypt the connection.
|
|
</li>
|
|
|
|
</ul>
|
|
|
|
<h3 id="vet_command">Go vet command</h3>
|
|
|
|
<p>
|
|
The <a href="/cmd/vet"><code>go tool vet</code></a> command now does
|
|
more thorough validation of struct tags.
|
|
</p>
|
|
|
|
<h3 id="trace_command">Trace command</h3>
|
|
|
|
<p>
|
|
A new tool is available for dynamic execution tracing of Go programs.
|
|
The usage is analogous to how the test coverage tool works.
|
|
Generation of traces is integrated into <code>go test</code>,
|
|
and then a separate execution of the tracing tool itself analyzes the results:
|
|
</p>
|
|
|
|
<pre>
|
|
$ go test -trace=trace.out path/to/package
|
|
$ go tool trace [flags] pkg.test trace.out
|
|
</pre>
|
|
|
|
<p>
|
|
The flags enable the output to be displayed in a browser window.
|
|
For details, run <code>go tool trace -help</code>.
|
|
There is also a description of the tracing facility in this
|
|
<a href="https://talks.golang.org/2015/dynamic-tools.slide">talk</a>
|
|
from GopherCon 2015.
|
|
</p>
|
|
|
|
<h3 id="doc_command">Go doc command</h3>
|
|
|
|
<p>
|
|
A few releases back, the <code>go doc</code>
|
|
command was deleted as being unnecessary.
|
|
One could always run "<code>godoc .</code>" instead.
|
|
The 1.5 release introduces a new <a href="/cmd/doc"><code>go doc</code></a>
|
|
command with a more convenient command-line interface than
|
|
<code>godoc</code>'s.
|
|
It is designed for command-line usage specifically, and provides a more
|
|
compact and focused presentation of the documentation for a package
|
|
or its elements, according to the invocation.
|
|
It also provides case-insensitive matching and
|
|
support for showing the documentation for unexported symbols.
|
|
For details run "<code>go help doc</code>".
|
|
</p>
|
|
|
|
<h3 id="cgo">Cgo</h3>
|
|
|
|
<p>
|
|
When parsing <code>#cgo</code> lines,
|
|
the invocation <code>${SRCDIR}</code> is now
|
|
expanded into the path to the source directory.
|
|
This allows options to be passed to the
|
|
compiler and linker that involve file paths relative to the
|
|
source code directory. Without the expansion the paths would be
|
|
invalid when the current working directory changes.
|
|
</p>
|
|
|
|
<p>
|
|
Solaris now has full cgo support.
|
|
</p>
|
|
|
|
<p>
|
|
On Windows, cgo now uses external linking by default.
|
|
</p>
|
|
|
|
<p>
|
|
When a C struct ends with a zero-sized field, but the struct itself is
|
|
not zero-sized, Go code can no longer refer to the zero-sized field.
|
|
Any such references will have to be rewritten.
|
|
</p>
|
|
|
|
<h2 id="performance">Performance</h2>
|
|
|
|
<p>
|
|
As always, the changes are so general and varied that precise statements
|
|
about performance are difficult to make.
|
|
The changes are even broader ranging than usual in this release, which
|
|
includes a new garbage collector and a conversion of the runtime to Go.
|
|
Some programs may run faster, some slower.
|
|
On average the programs in the Go 1 benchmark suite run a few percent faster in Go 1.5
|
|
than they did in Go 1.4,
|
|
while as mentioned above the garbage collector's pauses are
|
|
dramatically shorter, and almost always under 10 milliseconds.
|
|
</p>
|
|
|
|
<p>
|
|
Builds in Go 1.5 will be slower by a factor of about two.
|
|
The automatic translation of the compiler and linker from C to Go resulted in
|
|
unidiomatic Go code that performs poorly compared to well-written Go.
|
|
Analysis tools and refactoring helped to improve the code, but much remains to be done.
|
|
Further profiling and optimization will continue in Go 1.6 and future releases.
|
|
For more details, see these <a href="https://talks.golang.org/2015/gogo.slide">slides</a>
|
|
and associated <a href="https://www.youtube.com/watch?v=cF1zJYkBW4A">video</a>.
|
|
</p>
|
|
|
|
<h2 id="library">Core library</h2>
|
|
|
|
<h3 id="flag">Flag</h3>
|
|
|
|
<p>
|
|
The flag package's
|
|
<a href="/pkg/flag/#PrintDefaults"><code>PrintDefaults</code></a>
|
|
function, and method on <a href="/pkg/flag/#FlagSet"><code>FlagSet</code></a>,
|
|
have been modified to create nicer usage messages.
|
|
The format has been changed to be more human-friendly and in the usage
|
|
messages a word quoted with `backquotes` is taken to be the name of the
|
|
flag's operand to display in the usage message.
|
|
For instance, a flag created with the invocation,
|
|
</p>
|
|
|
|
<pre>
|
|
cpuFlag = flag.Int("cpu", 1, "run `N` processes in parallel")
|
|
</pre>
|
|
|
|
<p>
|
|
will show the help message,
|
|
</p>
|
|
|
|
<pre>
|
|
-cpu N
|
|
run N processes in parallel (default 1)
|
|
</pre>
|
|
|
|
<p>
|
|
Also, the default is now listed only when it is not the zero value for the type.
|
|
</p>
|
|
|
|
<h3 id="math_big">Floats in math/big</h3>
|
|
|
|
<p>
|
|
The <a href="/pkg/math/big/"><code>math/big</code></a> package
|
|
has a new, fundamental data type,
|
|
<a href="/pkg/math/big/#Float"><code>Float</code></a>,
|
|
which implements arbitrary-precision floating-point numbers.
|
|
A <code>Float</code> value is represented by a boolean sign,
|
|
a variable-length mantissa, and a 32-bit fixed-size signed exponent.
|
|
The precision of a <code>Float</code> (the mantissa size in bits)
|
|
can be specified explicitly or is otherwise determined by the first
|
|
operation that creates the value.
|
|
Once created, the size of a <code>Float</code>'s mantissa may be modified with the
|
|
<a href="/pkg/math/big/#Float.SetPrec"><code>SetPrec</code></a> method.
|
|
<code>Floats</code> support the concept of infinities, such as are created by
|
|
overflow, but values that would lead to the equivalent of IEEE 754 NaNs
|
|
trigger a panic.
|
|
<code>Float</code> operations support all IEEE-754 rounding modes.
|
|
When the precision is set to 24 (53) bits,
|
|
operations that stay within the range of normalized <code>float32</code>
|
|
(<code>float64</code>)
|
|
values produce the same results as the corresponding IEEE-754
|
|
arithmetic on those values.
|
|
</p>
|
|
|
|
<h3 id="go_types">Go types</h3>
|
|
|
|
<p>
|
|
The <a href="/pkg/go/types/"><code>go/types</code></a> package
|
|
up to now has been maintained in the <code>golang.org/x</code>
|
|
repository; as of Go 1.5 it has been relocated to the main repository.
|
|
The code at the old location is now deprecated.
|
|
There is also a modest API change in the package, discussed below.
|
|
</p>
|
|
|
|
<p>
|
|
Associated with this move, the
|
|
<a href="/pkg/go/constant/"><code>go/constant</code></a>
|
|
package also moved to the main repository;
|
|
it was <code>golang.org/x/tools/exact</code> before.
|
|
The <a href="/pkg/go/importer/"><code>go/importer</code></a> package
|
|
also moved to the main repository,
|
|
as well as some tools described above.
|
|
</p>
|
|
|
|
<h3 id="net">Net</h3>
|
|
|
|
<p>
|
|
The DNS resolver in the net package has almost always used <code>cgo</code> to access
|
|
the system interface.
|
|
A change in Go 1.5 means that on most Unix systems DNS resolution
|
|
will no longer require <code>cgo</code>, which simplifies execution
|
|
on those platforms.
|
|
Now, if the system's networking configuration permits, the native Go resolver
|
|
will suffice.
|
|
The important effect of this change is that each DNS resolution occupies a goroutine
|
|
rather than a thread,
|
|
so a program with multiple outstanding DNS requests will consume fewer operating
|
|
system resources.
|
|
</p>
|
|
|
|
<p>
|
|
The decision of how to run the resolver applies at run time, not build time.
|
|
The <code>netgo</code> build tag that has been used to enforce the use
|
|
of the Go resolver is no longer necessary, although it still works.
|
|
A new <code>netcgo</code> build tag forces the use of the <code>cgo</code> resolver at
|
|
build time.
|
|
To force <code>cgo</code> resolution at run time set
|
|
<code>GODEBUG=netdns=cgo</code> in the environment.
|
|
More debug options are documented <a href="https://golang.org/cl/11584">here</a>.
|
|
</p>
|
|
|
|
<p>
|
|
This change applies to Unix systems only.
|
|
Windows, Mac OS X, and Plan 9 systems behave as before.
|
|
</p>
|
|
|
|
<h3 id="reflect">Reflect</h3>
|
|
|
|
<p>
|
|
The <a href="/pkg/reflect/"><code>reflect</code></a> package
|
|
has two new functions: <a href="/pkg/reflect/#ArrayOf"><code>ArrayOf</code></a>
|
|
and <a href="/pkg/reflect/#FuncOf"><code>FuncOf</code></a>.
|
|
These functions, analogous to the extant
|
|
<a href="/pkg/reflect/#SliceOf"><code>SliceOf</code></a> function,
|
|
create new types at runtime to describe arrays and functions.
|
|
</p>
|
|
|
|
<h3 id="hardening">Hardening</h3>
|
|
|
|
<p>
|
|
Several dozen bugs were found in the standard library
|
|
through randomized testing with the
|
|
<a href="https://github.com/dvyukov/go-fuzz"><code>go-fuzz</code></a> tool.
|
|
Bugs were fixed in the
|
|
<a href="/pkg/archive/tar/"><code>archive/tar</code></a>,
|
|
<a href="/pkg/archive/zip/"><code>archive/zip</code></a>,
|
|
<a href="/pkg/compress/flate/"><code>compress/flate</code></a>,
|
|
<a href="/pkg/encoding/gob/"><code>encoding/gob</code></a>,
|
|
<a href="/pkg/fmt/"><code>fmt</code></a>,
|
|
<a href="/pkg/html/template/"><code>html/template</code></a>,
|
|
<a href="/pkg/image/gif/"><code>image/gif</code></a>,
|
|
<a href="/pkg/image/jpeg/"><code>image/jpeg</code></a>,
|
|
<a href="/pkg/image/png/"><code>image/png</code></a>, and
|
|
<a href="/pkg/text/template/"><code>text/template</code></a>,
|
|
packages.
|
|
The fixes harden the implementation against incorrect and malicious inputs.
|
|
</p>
|
|
|
|
<h3 id="minor_library_changes">Minor changes to the library</h3>
|
|
|
|
<ul>
|
|
|
|
<li>
|
|
The <a href="/pkg/archive/zip/"><code>archive/zip</code></a> package's
|
|
<a href="/pkg/archive/zip/#Writer"><code>Writer</code></a> type now has a
|
|
<a href="/pkg/archive/zip/#Writer.SetOffset"><code>SetOffset</code></a>
|
|
method to specify the location within the output stream at which to write the archive.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/bufio/#Reader"><code>Reader</code></a> in the
|
|
<a href="/pkg/bufio/"><code>bufio</code></a> package now has a
|
|
<a href="/pkg/bufio/#Reader.Discard"><code>Discard</code></a>
|
|
method to discard data from the input.
|
|
</li>
|
|
|
|
<li>
|
|
In the <a href="/pkg/bytes/"><code>bytes</code></a> package,
|
|
the <a href="/pkg/bytes/#Buffer"><code>Buffer</code></a> type
|
|
now has a <a href="/pkg/bytes/#Buffer.Cap"><code>Cap</code></a> method
|
|
that reports the number of bytes allocated within the buffer.
|
|
Similarly, in both the <a href="/pkg/bytes/"><code>bytes</code></a>
|
|
and <a href="/pkg/strings/"><code>strings</code></a> packages,
|
|
the <a href="/pkg/bytes/#Reader"><code>Reader</code></a>
|
|
type now has a <a href="/pkg/bytes/#Reader.Size"><code>Size</code></a>
|
|
method that reports the original length of the underlying slice or string.
|
|
</li>
|
|
|
|
<li>
|
|
Both the <a href="/pkg/bytes/"><code>bytes</code></a> and
|
|
<a href="/pkg/strings/"><code>strings</code></a> packages
|
|
also now have a <a href="/pkg/bytes/#LastIndexByte"><code>LastIndexByte</code></a>
|
|
function that locates the rightmost byte with that value in the argument.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/crypto/"><code>crypto</code></a> package
|
|
has a new interface, <a href="/pkg/crypto/#Decrypter"><code>Decrypter</code></a>,
|
|
that abstracts the behavior of a private key used in asymmetric decryption.
|
|
</li>
|
|
|
|
<li>
|
|
In the <a href="/pkg/crypto/cipher/"><code>crypto/cipher</code></a> package,
|
|
the documentation for the <a href="/pkg/crypto/cipher/#Stream"><code>Stream</code></a>
|
|
interface has been clarified regarding the behavior when the source and destination are
|
|
different lengths.
|
|
If the destination is shorter than the source, the method will panic.
|
|
This is not a change in the implementation, only the documentation.
|
|
</li>
|
|
|
|
<li>
|
|
Also in the <a href="/pkg/crypto/cipher/"><code>crypto/cipher</code></a> package,
|
|
there is now support for nonce lengths other than 96 bytes in AES's Galois/Counter mode (GCM),
|
|
which some protocols require.
|
|
</li>
|
|
|
|
<li>
|
|
In the <a href="/pkg/crypto/elliptic/"><code>crypto/elliptic</code></a> package,
|
|
there is now a <code>Name</code> field in the
|
|
<a href="/pkg/crypto/elliptic/#CurveParams"><code>CurveParams</code></a> struct,
|
|
and the curves implemented in the package have been given names.
|
|
These names provide a safer way to select a curve, as opposed to
|
|
selecting its bit size, for cryptographic systems that are curve-dependent.
|
|
</li>
|
|
|
|
<li>
|
|
Also in the <a href="/pkg/crypto/elliptic/"><code>crypto/elliptic</code></a> package,
|
|
the <a href="/pkg/crypto/elliptic/#Unmarshal"><code>Unmarshal</code></a> function
|
|
now verifies that the point is actually on the curve.
|
|
(If it is not, the function returns nils).
|
|
This change guards against certain attacks.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/crypto/sha512/"><code>crypto/sha512</code></a>
|
|
package now has support for the two truncated versions of
|
|
the SHA-512 hash algorithm, SHA-512/224 and SHA-512/256.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/crypto/tls/"><code>crypto/tls</code></a> package
|
|
minimum protocol version now defaults to TLS 1.0.
|
|
The old default, SSLv3, is still available through <a href="/pkg/crypto/tls/#Config"><code>Config</code></a> if needed.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/crypto/tls/"><code>crypto/tls</code></a> package
|
|
now supports Signed Certificate Timestamps (SCTs) as specified in RFC 6962.
|
|
The server serves them if they are listed in the
|
|
<a href="/pkg/crypto/tls/#Certificate"><code>Certificate</code></a> struct,
|
|
and the client requests them and exposes them, if present,
|
|
in its <a href="/pkg/crypto/tls/#ConnectionState"><code>ConnectionState</code></a> struct.
|
|
|
|
<li>
|
|
The stapled OCSP response to a <a href="/pkg/crypto/tls/"><code>crypto/tls</code></a> client connection,
|
|
previously only available via the
|
|
<a href="/pkg/crypto/tls/#Conn.OCSPResponse"><code>OCSPResponse</code></a> method,
|
|
is now exposed in the <a href="/pkg/crypto/tls/#ConnectionState"><code>ConnectionState</code></a> struct.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/crypto/tls/"><code>crypto/tls</code></a> server implementation
|
|
will now always call the
|
|
<code>GetCertificate</code> function in
|
|
the <a href="/pkg/crypto/tls/#Config"><code>Config</code></a> struct
|
|
to select a certificate for the connection when none is supplied.
|
|
</li>
|
|
|
|
<li>
|
|
Finally, the session ticket keys in the
|
|
<a href="/pkg/crypto/tls/"><code>crypto/tls</code></a> package
|
|
can now be changed while the server is running.
|
|
This is done through the new
|
|
<a href="/pkg/crypto/tls/#Config.SetSessionTicketKeys"><code>SetSessionTicketKeys</code></a>
|
|
method of the
|
|
<a href="/pkg/crypto/tls/#Config"><code>Config</code></a> type.
|
|
</li>
|
|
|
|
<li>
|
|
In the <a href="/pkg/crypto/x509/"><code>crypto/x509</code></a> package,
|
|
wildcards are now accepted only in the leftmost label as defined in
|
|
<a href="https://tools.ietf.org/html/rfc6125#section-6.4.3">the specification</a>.
|
|
</li>
|
|
|
|
<li>
|
|
Also in the <a href="/pkg/crypto/x509/"><code>crypto/x509</code></a> package,
|
|
the handling of unknown critical extensions has been changed.
|
|
They used to cause parse errors but now they are parsed and caused errors only
|
|
in <a href="/pkg/crypto/x509/#Certificate.Verify"><code>Verify</code></a>.
|
|
The new field <code>UnhandledCriticalExtensions</code> of
|
|
<a href="/pkg/crypto/x509/#Certificate"><code>Certificate</code></a> records these extensions.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/database/sql/#DB"><code>DB</code></a> type of the
|
|
<a href="/pkg/database/sql/"><code>database/sql</code></a> package
|
|
now has a <a href="/pkg/database/sql/#DB.Stats"><code>Stats</code></a> method
|
|
to retrieve database statistics.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/debug/dwarf/"><code>debug/dwarf</code></a>
|
|
package has extensive additions to better support DWARF version 4.
|
|
See for example the definition of the new type
|
|
<a href="/pkg/debug/dwarf/#Class"><code>Class</code></a>.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/debug/dwarf/"><code>debug/dwarf</code></a> package
|
|
also now supports decoding of DWARF line tables.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/debug/elf/"><code>debug/elf</code></a>
|
|
package now has support for the 64-bit PowerPC architecture.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/encoding/base64/"><code>encoding/base64</code></a> package
|
|
now supports unpadded encodings through two new encoding variables,
|
|
<a href="/pkg/encoding/base64/#RawStdEncoding"><code>RawStdEncoding</code></a> and
|
|
<a href="/pkg/encoding/base64/#RawURLEncoding"><code>RawURLEncoding</code></a>.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/encoding/json/"><code>encoding/json</code></a> package
|
|
now returns an <a href="/pkg/encoding/json/#UnmarshalTypeError"><code>UnmarshalTypeError</code></a>
|
|
if a JSON value is not appropriate for the target variable or component
|
|
to which it is being unmarshaled.
|
|
</li>
|
|
|
|
<li>
|
|
The <code>encoding/json</code>'s
|
|
<a href="/pkg/encoding/json/#Decoder"><code>Decoder</code></a>
|
|
type has a new method that provides a streaming interface for decoding
|
|
a JSON document:
|
|
<a href="/pkg/encoding/json/#Decoder.Token"><code>Token</code></a>.
|
|
It also interoperates with the existing functionality of <code>Decode</code>,
|
|
which will continue a decode operation already started with <code>Decoder.Token</code>.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/flag/"><code>flag</code></a> package
|
|
has a new function, <a href="/pkg/flag/#UnquoteUsage"><code>UnquoteUsage</code></a>,
|
|
to assist in the creation of usage messages using the new convention
|
|
described above.
|
|
</li>
|
|
|
|
<li>
|
|
In the <a href="/pkg/fmt/"><code>fmt</code></a> package,
|
|
a value of type <a href="/pkg/reflect/#Value"><code>Value</code></a> now
|
|
prints what it holds, rather than use the <code>reflect.Value</code>'s <code>Stringer</code>
|
|
method, which produces things like <code><int Value></code>.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/ast/#EmptyStmt"><code>EmptyStmt</code></a> type
|
|
in the <a href="/pkg/go/ast/"><code>go/ast</code></a> package now
|
|
has a boolean <code>Implicit</code> field that records whether the
|
|
semicolon was implicitly added or was present in the source.
|
|
</li>
|
|
|
|
<li>
|
|
For forward compatibility the <a href="/pkg/go/build/"><code>go/build</code></a> package
|
|
reserves <code>GOARCH</code> values for a number of architectures that Go might support one day.
|
|
This is not a promise that it will.
|
|
Also, the <a href="/pkg/go/build/#Package"><code>Package</code></a> struct
|
|
now has a <code>PkgTargetRoot</code> field that stores the
|
|
architecture-dependent root directory in which to install, if known.
|
|
</li>
|
|
|
|
<li>
|
|
The (newly migrated) <a href="/pkg/go/types/"><code>go/types</code></a>
|
|
package allows one to control the prefix attached to package-level names using
|
|
the new <a href="/pkg/go/types/#Qualifier"><code>Qualifier</code></a>
|
|
function type as an argument to several functions. This is an API change for
|
|
the package, but since it is new to the core, it is not breaking the Go 1 compatibility
|
|
rules since code that uses the package must explicitly ask for it at its new location.
|
|
To update, run
|
|
<a href="https://golang.org/cmd/go/#hdr-Run_go_tool_fix_on_packages"><code>go fix</code></a> on your package.
|
|
</li>
|
|
|
|
<li>
|
|
In the <a href="/pkg/image/"><code>image</code></a> package,
|
|
the <a href="/pkg/image/#Rectangle"><code>Rectangle</code></a> type
|
|
now implements the <a href="/pkg/image/#Image"><code>Image</code></a> interface,
|
|
so a <code>Rectangle</code> can serve as a mask when drawing.
|
|
</li>
|
|
|
|
<li>
|
|
Also in the <a href="/pkg/image/"><code>image</code></a> package,
|
|
to assist in the handling of some JPEG images,
|
|
there is now support for 4:1:1 and 4:1:0 YCbCr subsampling and basic
|
|
CMYK support, represented by the new <code>image.CMYK</code> struct.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/image/color/"><code>image/color</code></a> package
|
|
adds basic CMYK support, through the new
|
|
<a href="/pkg/image/color/#CMYK"><code>CMYK</code></a> struct,
|
|
the <a href="/pkg/image/color/#CMYKModel"><code>CMYKModel</code></a> color model, and the
|
|
<a href="/pkg/image/color/#CMYKToRGB"><code>CMYKToRGB</code></a> function, as
|
|
needed by some JPEG images.
|
|
</li>
|
|
|
|
<li>
|
|
Also in the <a href="/pkg/image/color/"><code>image/color</code></a> package,
|
|
the conversion of a <a href="/pkg/image/color/#YCbCr"><code>YCbCr</code></a>
|
|
value to <code>RGBA</code> has become more precise.
|
|
Previously, the low 8 bits were just an echo of the high 8 bits;
|
|
now they contain more accurate information.
|
|
Because of the echo property of the old code, the operation
|
|
<code>uint8(r)</code> to extract an 8-bit red value worked, but is incorrect.
|
|
In Go 1.5, that operation may yield a different value.
|
|
The correct code is, and always was, to select the high 8 bits:
|
|
<code>uint8(r>>8)</code>.
|
|
Incidentally, the <code>image/draw</code> package
|
|
provides better support for such conversions; see
|
|
<a href="https://blog.golang.org/go-imagedraw-package">this blog post</a>
|
|
for more information.
|
|
</li>
|
|
|
|
<li>
|
|
Finally, as of Go 1.5 the closest match check in
|
|
<a href="/pkg/image/color/#Palette.Index"><code>Index</code></a>
|
|
now honors the alpha channel.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/image/gif/"><code>image/gif</code></a> package
|
|
includes a couple of generalizations.
|
|
A multiple-frame GIF file can now have an overall bounds different
|
|
from all the contained single frames' bounds.
|
|
Also, the <a href="/pkg/image/gif/#GIF"><code>GIF</code></a> struct
|
|
now has a <code>Disposal</code> field
|
|
that specifies the disposal method for each frame.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/io/"><code>io</code></a> package
|
|
adds a <a href="/pkg/io/#CopyBuffer"><code>CopyBuffer</code></a> function
|
|
that is like <a href="/pkg/io/#Copy"><code>Copy</code></a> but
|
|
uses a caller-provided buffer, permitting control of allocation and buffer size.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/log/"><code>log</code></a> package
|
|
has a new <a href="/pkg/log/#LUTC"><code>LUTC</code></a> flag
|
|
that causes time stamps to be printed in the UTC time zone.
|
|
It also adds a <a href="/pkg/log/#Logger.SetOutput"><code>SetOutput</code></a> method
|
|
for user-created loggers.
|
|
</li>
|
|
|
|
<li>
|
|
In Go 1.4, <a href="/pkg/math/#Max"><code>Max</code></a> was not detecting all possible NaN bit patterns.
|
|
This is fixed in Go 1.5, so programs that use <code>math.Max</code> on data including NaNs may behave differently,
|
|
but now correctly according to the IEEE754 definition of NaNs.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/math/big/"><code>math/big</code></a> package
|
|
adds a new <a href="/pkg/math/big/#Jacobi"><code>Jacobi</code></a>
|
|
function for integers and a new
|
|
<a href="/pkg/math/big/#Int.ModSqrt"><code>ModSqrt</code></a>
|
|
method for the <a href="/pkg/math/big/#Int"><code>Int</code></a> type.
|
|
</li>
|
|
|
|
<li>
|
|
The mime package
|
|
adds a new <a href="/pkg/mime/#WordDecoder"><code>WordDecoder</code></a> type
|
|
to decode MIME headers containing RFC 204-encoded words.
|
|
It also provides <a href="/pkg/mime/#BEncoding"><code>BEncoding</code></a> and
|
|
<a href="/pkg/mime/#QEncoding"><code>QEncoding</code></a>
|
|
as implementations of the encoding schemes of RFC 2045 and RFC 2047.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/mime/"><code>mime</code></a> package also adds an
|
|
<a href="/pkg/mime/#ExtensionsByType"><code>ExtensionsByType</code></a>
|
|
function that returns the MIME extensions know to be associated with a given MIME type.
|
|
</li>
|
|
|
|
<li>
|
|
There is a new <a href="/pkg/mime/quotedprintable/"><code>mime/quotedprintable</code></a>
|
|
package that implements the quoted-printable encoding defined by RFC 2045.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/net/"><code>net</code></a> package will now
|
|
<a href="/pkg/net/#Dial"><code>Dial</code></a> hostnames by trying each
|
|
IP address in order until one succeeds.
|
|
The <code><a href="/pkg/net/#Dialer">Dialer</a>.DualStack</code>
|
|
mode now implements Happy Eyeballs
|
|
(<a href="https://tools.ietf.org/html/rfc6555">RFC 6555</a>) by giving the
|
|
first address family a 300ms head start; this value can be overridden by
|
|
the new <code>Dialer.FallbackDelay</code>.
|
|
</li>
|
|
|
|
<li>
|
|
A number of inconsistencies in the types returned by errors in the
|
|
<a href="/pkg/net/"><code>net</code></a> package have been
|
|
tidied up.
|
|
Most now return an
|
|
<a href="/pkg/net/#OpError"><code>OpError</code></a> value
|
|
with more information than before.
|
|
Also, the <a href="/pkg/net/#OpError"><code>OpError</code></a>
|
|
type now includes a <code>Source</code> field that holds the local
|
|
network address.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/net/http/"><code>net/http</code></a> package now
|
|
has support for setting trailers from a server <a href="/pkg/net/http/#Handler"><code>Handler</code></a>.
|
|
For details, see the documentation for
|
|
<a href="/pkg/net/http/#ResponseWriter"><code>ResponseWriter</code></a>.
|
|
</li>
|
|
|
|
<li>
|
|
There is a new method to cancel a <a href="/pkg/net/http/"><code>net/http</code></a>
|
|
<code>Request</code> by setting the new
|
|
<a href="/pkg/net/http/#Request"><code>Request.Cancel</code></a>
|
|
field.
|
|
It is supported by <code>http.Transport</code>.
|
|
The <code>Cancel</code> field's type is compatible with the
|
|
<a href="https://godoc.org/golang.org/x/net/context"><code>context.Context.Done</code></a>
|
|
return value.
|
|
</li>
|
|
|
|
<li>
|
|
Also in the <a href="/pkg/net/http/"><code>net/http</code></a> package,
|
|
there is code to ignore the zero <a href="/pkg/time/#Time"><code>Time</code></a> value
|
|
in the <a href="/pkg/net/#ServeContent"><code>ServeContent</code></a> function.
|
|
As of Go 1.5, it now also ignores a time value equal to the Unix epoch.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/net/http/fcgi/"><code>net/http/fcgi</code></a> package
|
|
exports two new errors,
|
|
<a href="/pkg/net/http/fcgi/#ErrConnClosed"><code>ErrConnClosed</code></a> and
|
|
<a href="/pkg/net/http/fcgi/#ErrRequestAborted"><code>ErrRequestAborted</code></a>,
|
|
to report the corresponding error conditions.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/net/http/cgi/"><code>net/http/cgi</code></a> package
|
|
had a bug that mishandled the values of the environment variables
|
|
<code>REMOTE_ADDR</code> and <code>REMOTE_HOST</code>.
|
|
This has been fixed.
|
|
Also, starting with Go 1.5 the package sets the <code>REMOTE_PORT</code>
|
|
variable.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/net/mail/"><code>net/mail</code></a> package
|
|
adds an <a href="/pkg/net/mail/#AddressParser"><code>AddressParser</code></a>
|
|
type that can parse mail addresses.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/net/smtp/"><code>net/smtp</code></a> package
|
|
now has a <a href="/pkg/net/smtp/#Client.TLSConnectionState"><code>TLSConnectionState</code></a>
|
|
accessor to the <a href="/pkg/net/smtp/#Client"><code>Client</code></a>
|
|
type that returns the client's TLS state.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/os/"><code>os</code></a> package
|
|
has a new <a href="/pkg/os/#LookupEnv"><code>LookupEnv</code></a> function
|
|
that is similar to <a href="/pkg/os/#Getenv"><code>Getenv</code></a>
|
|
but can distinguish between an empty environment variable and a missing one.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/os/signal/"><code>os/signal</code></a> package
|
|
adds new <a href="/pkg/os/signal/#Ignore"><code>Ignore</code></a> and
|
|
<a href="/pkg/os/signal/#Reset"><code>Reset</code></a> functions.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/runtime/"><code>runtime</code></a>,
|
|
<a href="/pkg/runtime/trace/"><code>runtime/trace</code></a>,
|
|
and <a href="/pkg/net/http/pprof/"><code>net/http/pprof</code></a> packages
|
|
each have new functions to support the tracing facilities described above:
|
|
<a href="/pkg/runtime/#ReadTrace"><code>ReadTrace</code></a>,
|
|
<a href="/pkg/runtime/#StartTrace"><code>StartTrace</code></a>,
|
|
<a href="/pkg/runtime/#StopTrace"><code>StopTrace</code></a>,
|
|
<a href="/pkg/runtime/trace/#Start"><code>Start</code></a>,
|
|
<a href="/pkg/runtime/trace/#Stop"><code>Stop</code></a>, and
|
|
<a href="/pkg/net/http/pprof/#Trace"><code>Trace</code></a>.
|
|
See the respective documentation for details.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/runtime/pprof/"><code>runtime/pprof</code></a> package
|
|
by default now includes overall memory statistics in all memory profiles.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/strings/"><code>strings</code></a> package
|
|
has a new <a href="/pkg/strings/#Compare"><code>Compare</code></a> function.
|
|
This is present to provide symmetry with the <a href="/pkg/bytes/"><code>bytes</code></a> package
|
|
but is otherwise unnecessary as strings support comparison natively.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/sync/#WaitGroup"><code>WaitGroup</code></a> implementation in
|
|
package <a href="/pkg/sync/"><code>sync</code></a>
|
|
now diagnoses code that races a call to <a href="/pkg/sync/#WaitGroup.Add"><code>Add</code></a>
|
|
against a return from <a href="/pkg/sync/#WaitGroup.Wait"><code>Wait</code></a>.
|
|
If it detects this condition, the implementation panics.
|
|
</li>
|
|
|
|
<li>
|
|
In the <a href="/pkg/syscall/"><code>syscall</code></a> package,
|
|
the Linux <code>SysProcAttr</code> struct now has a
|
|
<code>GidMappingsEnableSetgroups</code> field, made necessary
|
|
by security changes in Linux 3.19.
|
|
On all Unix systems, the struct also has new <code>Foreground</code> and <code>Pgid</code> fields
|
|
to provide more control when exec'ing.
|
|
On Darwin, there is now a <code>Syscall9</code> function
|
|
to support calls with too many arguments.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/testing/quick/"><code>testing/quick</code></a> will now
|
|
generate <code>nil</code> values for pointer types,
|
|
making it possible to use with recursive data structures.
|
|
Also, the package now supports generation of array types.
|
|
</li>
|
|
|
|
<li>
|
|
In the <a href="/pkg/text/template/"><code>text/template</code></a> and
|
|
<a href="/pkg/html/template/"><code>html/template</code></a> packages,
|
|
integer constants too large to be represented as a Go integer now trigger a
|
|
parse error. Before, they were silently converted to floating point, losing
|
|
precision.
|
|
</li>
|
|
|
|
<li>
|
|
Also in the <a href="/pkg/text/template/"><code>text/template</code></a> and
|
|
<a href="/pkg/html/template/"><code>html/template</code></a> packages,
|
|
a new <a href="/pkg/text/template/#Template.Option"><code>Option</code></a> method
|
|
allows customization of the behavior of the template during execution.
|
|
The sole implemented option allows control over how a missing key is
|
|
handled when indexing a map.
|
|
The default, which can now be overridden, is as before: to continue with an invalid value.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/time/"><code>time</code></a> package's
|
|
<code>Time</code> type has a new method
|
|
<a href="/pkg/time/#Time.AppendFormat"><code>AppendFormat</code></a>,
|
|
which can be used to avoid allocation when printing a time value.
|
|
</li>
|
|
|
|
<li>
|
|
The <a href="/pkg/unicode/"><code>unicode</code></a> package and associated
|
|
support throughout the system has been upgraded from version 7.0 to
|
|
<a href="http://www.unicode.org/versions/Unicode8.0.0/">Unicode 8.0</a>.
|
|
</li>
|
|
|
|
</ul>
|