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diff --git a/doc/go1.5.html b/doc/go1.5.html deleted file mode 100644 index 2c77cf4169..0000000000 --- a/doc/go1.5.html +++ /dev/null @@ -1,1310 +0,0 @@ -<!--{ - "Title": "Go 1.5 Release Notes", - "Path": "/doc/go1.5", - "Template": true -}--> - - -<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{ - Point{29.935523, 52.891566}: "Persepolis", - Point{-25.352594, 131.034361}: "Uluru", - Point{37.422455, -122.084306}: "Googleplex", -} -</pre> - -<p> -may be written as follows, without the <code>Point</code> type listed explicitly: -</p> - -<pre> -m := map[Point]string{ - {29.935523, 52.891566}: "Persepolis", - {-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> |