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diff --git a/doc/go1.20.html b/doc/go1.20.html new file mode 100644 index 0000000..1fef452 --- /dev/null +++ b/doc/go1.20.html @@ -0,0 +1,1246 @@ +<!--{ + "Title": "Go 1.20 Release Notes", + "Path": "/doc/go1.20" +}--> + +<!-- +NOTE: In this document and others in this directory, the convention is to +set fixed-width phrases with non-fixed-width spaces, as in +<code>hello</code> <code>world</code>. +Do not send CLs removing the interior tags from such phrases. +--> + +<style> + main ul li { margin: 0.5em 0; } +</style> + +<h2 id="introduction">DRAFT RELEASE NOTES — Introduction to Go 1.20</h2> + +<p> + <strong> + Go 1.20 is not yet released. These are work-in-progress + release notes. Go 1.20 is expected to be released in February 2023. + </strong> +</p> + +<h2 id="language">Changes to the language</h2> + +<p> + Go 1.20 includes four changes to the language. +</p> + +<p><!-- https://go.dev/issue/46505 --> + Go 1.17 added <a href="/ref/spec#Conversions_from_slice_to_array_or_array_pointer">conversions from slice to an array pointer</a>. + Go 1.20 extends this to allow conversions from a slice to an array: + given a slice <code>x</code>, <code>[4]byte(x)</code> can now be written + instead of <code>*(*[4]byte)(x)</code>. +</p> + +<p><!-- https://go.dev/issue/53003 --> + The <a href="/ref/spec/#Package_unsafe"><code>unsafe</code> package</a> defines + three new functions <code>SliceData</code>, <code>String</code>, and <code>StringData</code>. + Along with Go 1.17's <code>Slice</code>, these functions now provide the complete ability to + construct and deconstruct slice and string values, without depending on their exact representation. +</p> + +<p><!-- https://go.dev/issue/8606 --> + The specification now defines that struct values are compared one field at a time, + considering fields in the order they appear in the struct type definition, + and stopping at the first mismatch. + The specification could previously have been read as if + all fields needed to be compared beyond the first mismatch. + Similarly, the specification now defines that array values are compared + one element at a time, in increasing index order. + In both cases, the difference affects whether certain comparisons must panic. + Existing programs are unchanged: the new spec wording describes + what the implementations have always done. +</p> + +<p><!-- https://go.dev/issue/56548 --> + <a href="/ref/spec#Comparison_operators">Comparable types</a> (such as ordinary interfaces) + may now satisfy <code>comparable</code> constraints, even if the type arguments + are not strictly comparable (comparison may panic at runtime). + This makes it possible to instantiate a type parameter constrained by <code>comparable</code> + (e.g., a type parameter for a user-defined generic map key) with a non-strictly comparable type argument + such as an interface type, or a composite type containing an interface type. +</p> + +<h2 id="ports">Ports</h2> + +<h3 id="windows">Windows</h3> + +<p><!-- https://go.dev/issue/57003, https://go.dev/issue/57004 --> + Go 1.20 is the last release that will run on any release of Windows 7, 8, Server 2008 and Server 2012. + Go 1.21 will require at least Windows 10 or Server 2016. +</p> + +<h3 id="darwin">Darwin and iOS</h3> + +<p><!-- https://go.dev/issue/23011 --> + Go 1.20 is the last release that will run on macOS 10.13 High Sierra or 10.14 Mojave. + Go 1.21 will require macOS 10.15 Catalina or later. +</p> + +<h3 id="freebsd-riscv">FreeBSD/RISC-V</h3> + +<p><!-- https://go.dev/issue/53466 --> + Go 1.20 adds experimental support for FreeBSD on RISC-V (<code>GOOS=freebsd</code>, <code>GOARCH=riscv64</code>). +</p> + +<h2 id="tools">Tools</h2> + +<h3 id="go-command">Go command</h3> + +<p><!-- CL 432535, https://go.dev/issue/47257 --> + The directory <code>$GOROOT/pkg</code> no longer stores + pre-compiled package archives for the standard library: + <code>go</code> <code>install</code> no longer writes them, + the <code>go</code> build no longer checks for them, + and the Go distribution no longer ships them. + Instead, packages in the standard library are built as needed + and cached in the build cache, just like packages outside <code>GOROOT</code>. + This change reduces the size of the Go distribution and also + avoids C toolchain skew for packages that use cgo. +</p> + +<p><!-- CL 448357: cmd/go: print test2json start events --> + The implementation of <code>go</code> <code>test</code> <code>-json</code> + has been improved to make it more robust. + Programs that run <code>go</code> <code>test</code> <code>-json</code> + do not need any updates. + Programs that invoke <code>go</code> <code>tool</code> <code>test2json</code> + directly should now run the test binary with <code>-v=test2json</code> + (for example, <code>go</code> <code>test</code> <code>-v=test2json</code> + or <code>./pkg.test</code> <code>-test.v=test2json</code>) + instead of plain <code>-v</code>. +</p> + +<p><!-- CL 448357: cmd/go: print test2json start events --> + A related change to <code>go</code> <code>test</code> <code>-json</code> + is the addition of an event with <code>Action</code> set to <code>start</code> + at the beginning of each test program's execution. + When running multiple tests using the <code>go</code> command, + these start events are guaranteed to be emitted in the same order as + the packages named on the command line. +</p> + +<p><!-- https://go.dev/issue/45454, CL 421434 --> + The <code>go</code> command now defines + architecture feature build tags, such as <code>amd64.v2</code>, + to allow selecting a package implementation file based on the presence + or absence of a particular architecture feature. + See <a href="/cmd/go#hdr-Build_constraints"><code>go</code> <code>help</code> <code>buildconstraint</code></a> for details. +</p> + +<p><!-- https://go.dev/issue/50332 --> + The <code>go</code> subcommands now accept + <code>-C</code> <code><dir></code> to change directory to <dir> + before performing the command, which may be useful for scripts that need to + execute commands in multiple different modules. +</p> + +<p><!-- https://go.dev/issue/41696, CL 416094 --> + The <code>go</code> <code>build</code> and <code>go</code> <code>test</code> + commands no longer accept the <code>-i</code> flag, + which has been <a href="https://go.dev/issue/41696">deprecated since Go 1.16</a>. +</p> + +<p><!-- https://go.dev/issue/38687, CL 421440 --> + The <code>go</code> <code>generate</code> command now accepts + <code>-skip</code> <code><pattern></code> to skip <code>//go:generate</code> directives + matching <code><pattern></code>. +</p> + +<p><!-- https://go.dev/issue/41583 --> + The <code>go</code> <code>test</code> command now accepts + <code>-skip</code> <code><pattern></code> to skip tests, subtests, or examples + matching <code><pattern></code>. +</p> + +<p><!-- https://go.dev/issue/37015 --> + When the main module is located within <code>GOPATH/src</code>, + <code>go</code> <code>install</code> no longer installs libraries for + non-<code>main</code> packages to <code>GOPATH/pkg</code>, + and <code>go</code> <code>list</code> no longer reports a <code>Target</code> + field for such packages. (In module mode, compiled packages are stored in the + <a href="https://pkg.go.dev/cmd/go#hdr-Build_and_test_caching">build cache</a> + only, but <a href="https://go.dev/issue/37015">a bug</a> had caused + the <code>GOPATH</code> install targets to unexpectedly remain in effect.) +</p> + +<p><!-- https://go.dev/issue/55022 --> + The <code>go</code> <code>build</code>, <code>go</code> <code>install</code>, + and other build-related commands now support a <code>-pgo</code> flag that enables + profile-guided optimization, which is described in more detail in the + <a href="#compiler">Compiler</a> section below. + The <code>-pgo</code> flag specifies the file path of the profile. + Specifying <code>-pgo=auto</code> causes the <code>go</code> command to search + for a file named <code>default.pgo</code> in the main package's directory and + use it if present. + This mode currently requires a single main package to be specified on the + command line, but we plan to lift this restriction in a future release. + Specifying <code>-pgo=off</code> turns off profile-guided optimization. +</p> + +<p><!-- https://go.dev/issue/51430 --> + The <code>go</code> <code>build</code>, <code>go</code> <code>install</code>, + and other build-related commands now support a <code>-cover</code> + flag that builds the specified target with code coverage instrumentation. + This is described in more detail in the + <a href="#cover">Cover</a> section below. +</p> + +<h4 id="go-version"><code>go</code> <code>version</code></h4> + +<p><!-- https://go.dev/issue/48187 --> + The <code>go</code> <code>version</code> <code>-m</code> command + now supports reading more types of Go binaries, most notably, Windows DLLs + built with <code>go</code> <code>build</code> <code>-buildmode=c-shared</code> + and Linux binaries without execute permission. +</p> + +<h3 id="cgo">Cgo</h3> + +<p><!-- CL 450739 --> + The <code>go</code> command now disables <code>cgo</code> by default + on systems without a C toolchain. + More specifically, when the <code>CGO_ENABLED</code> environment variable is unset, + the <code>CC</code> environment variable is unset, + and the default C compiler (typically <code>clang</code> or <code>gcc</code>) + is not found in the path, + <code>CGO_ENABLED</code> defaults to <code>0</code>. + As always, you can override the default by setting <code>CGO_ENABLED</code> explicitly. +</p> + +<p> + The most important effect of the default change is that when Go is installed + on a system without a C compiler, it will now use pure Go builds for packages + in the standard library that use cgo, instead of using pre-distributed package archives + (which have been removed, as <a href="#go-command">noted above</a>) + or attempting to use cgo and failing. + This makes Go work better in some minimal container environments + as well as on macOS, where pre-distributed package archives have + not been used for cgo-based packages since Go 1.16. +</p> + +<p> + The packages in the standard library that use cgo are <a href="/pkg/net/"><code>net</code></a>, + <a href="/pkg/os/user/"><code>os/user</code></a>, and + <a href="/pkg/plugin/"><code>plugin</code></a>. + On macOS, the <code>net</code> and <code>os/user</code> packages have been rewritten not to use cgo: + the same code is now used for cgo and non-cgo builds as well as cross-compiled builds. + On Windows, the <code>net</code> and <code>os/user</code> packages have never used cgo. + On other systems, builds with cgo disabled will use a pure Go version of these packages. +</p> + +<p> + On macOS, the race detector has been rewritten not to use cgo: + race-detector-enabled programs can be built and run without Xcode. + On Linux and other Unix systems, and on Windows, a host C toolchain + is required to use the race detector. +</p> + +<h3 id="cover">Cover</h3> + +<p><!-- CL 436236, CL 401236, CL 438503 --> + Go 1.20 supports collecting code coverage profiles for programs + (applications and integration tests), as opposed to just unit tests. +</p> + +<p> + To collect coverage data for a program, build it with <code>go</code> + <code>build</code>'s <code>-cover</code> flag, then run the resulting + binary with the environment variable <code>GOCOVERDIR</code> set + to an output directory for coverage profiles. + See the + <a href="https://go.dev/testing/coverage">'coverage for integration tests' landing page</a> for more on how to get started. + For details on the design and implementation, see the + <a href="https://golang.org/issue/51430">proposal</a>. +</p> + +<h3 id="vet">Vet</h3> + +<h4 id="vet-loopclosure">Improved detection of loop variable capture by nested functions</h4> + +<p><!-- CL 447256, https://go.dev/issue/55972: extend the loopclosure analysis to parallel subtests --> + The <code>vet</code> tool now reports references to loop variables following + a call to <a href="/pkg/testing/#T.Parallel"><code>T.Parallel()</code></a> + within subtest function bodies. Such references may observe the value of the + variable from a different iteration (typically causing test cases to be + skipped) or an invalid state due to unsynchronized concurrent access. +</p> + +<p><!-- CL 452615 --> + The tool also detects reference mistakes in more places. Previously it would + only consider the last statement of the loop body, but now it recursively + inspects the last statements within if, switch, and select statements. +</p> + +<h4 id="vet-timeformat">New diagnostic for incorrect time formats</h4> + +<p><!-- CL 354010, https://go.dev/issue/48801: check for time formats with 2006-02-01 --> + The vet tool now reports use of the time format 2006-02-01 (yyyy-dd-mm) + with <a href="/pkg/time/#Time.Format"><code>Time.Format</code></a> and + <a href="/pkg/time/#Parse"><code>time.Parse</code></a>. + This format does not appear in common date standards, but is frequently + used by mistake when attempting to use the ISO 8601 date format + (yyyy-mm-dd). +</p> + +<h2 id="runtime">Runtime</h2> + +<p><!-- CL 422634 --> + Some of the garbage collector's internal data structures were reorganized to + be both more space and CPU efficient. + This change reduces memory overheads and improves overall CPU performance by + up to 2%. +</p> + +<p><!-- CL 417558, https://go.dev/issue/53892 --> + The garbage collector behaves less erratically with respect to goroutine + assists in some circumstances. +</p> + +<p><!-- https://go.dev/issue/51430 --> + Go 1.20 adds a new <code>runtime/coverage</code> package + containing APIs for writing coverage profile data at + runtime from long-running and/or server programs that + do not terminate via <code>os.Exit()</code>. +</p> + +<h2 id="compiler">Compiler</h2> + +<p><!-- https://go.dev/issue/55022 --> + Go 1.20 adds preview support for profile-guided optimization (PGO). + PGO enables the toolchain to perform application- and workload-specific + optimizations based on run-time profile information. + Currently, the compiler supports pprof CPU profiles, which can be collected + through usual means, such as the <code>runtime/pprof</code> or + <code>net/http/pprof</code> packages. + To enable PGO, pass the path of a pprof profile file via the + <code>-pgo</code> flag to <code>go</code> <code>build</code>, + as mentioned <a href="#go-command">above</a>. + Go 1.20 uses PGO to more aggressively inline functions at hot call sites. + Benchmarks for a representative set of Go programs show enabling + profile-guided inlining optimization improves performance about 3–4%. + We plan to add more profile-guided optimizations in future releases. + Note that profile-guided optimization is a preview, so please use it + with appropriate caution. +</p> + +<p> + The Go 1.20 compiler upgraded its front-end to use a new way of handling the + compiler's internal data, which fixes several generic-types bugs and enables + local types in generic functions and methods. +</p> + +<p><!-- https://go.dev/issue/56103, CL 445598 --> + The compiler now <a href="https://go.dev/issue/56103">disallows anonymous interface cycles</a>. +</p> + +<p><!-- https://go.dev/issue/49569 --> + Go 1.18 and 1.19 saw regressions in build speed, largely due to the addition + of support for generics and follow-on work. Go 1.20 improves build speeds by + up to 10%, bringing it back in line with Go 1.17. + Relative to Go 1.19, generated code performance is also generally slightly improved. +</p> + +<h2 id="linker">Linker</h2> + +<p><!-- https://go.dev/issue/54197, CL 420774 --> + On Linux, the linker now selects the dynamic interpreter for <code>glibc</code> + or <code>musl</code> at link time. +</p> + +<p><!-- https://go.dev/issue/35006 --> + On Windows, the Go linker now supports modern LLVM-based C toolchains. +</p> + +<p><!-- https://go.dev/issue/37762, CL 317917 --> + Go 1.20 uses <code>go:</code> and <code>type:</code> prefixes for compiler-generated + symbols rather than <code>go.</code> and <code>type.</code>. + This avoids confusion for user packages whose name starts with <code>go.</code>. + The <a href="/pkg/debug/gosym"><code>debug/gosym</code></a> package understands + this new naming convention for binaries built with Go 1.20 and newer. +</p> + +<h2 id="bootstrap">Bootstrap</h2> + +<p><!-- https://go.dev/issue/44505 --> + When building a Go release from source and <code>GOROOT_BOOTSTRAP</code> is not set, + previous versions of Go looked for a Go 1.4 or later bootstrap toolchain in the directory + <code>$HOME/go1.4</code> (<code>%HOMEDRIVE%%HOMEPATH%\go1.4</code> on Windows). + Go 1.18 and Go 1.19 looked first for <code>$HOME/go1.17</code> or <code>$HOME/sdk/go1.17</code> + before falling back to <code>$HOME/go1.4</code>, + in anticipation of requiring Go 1.17 for use when bootstrapping Go 1.20. + Go 1.20 does require a Go 1.17 release for bootstrapping, but we realized that we should + adopt the latest point release of the bootstrap toolchain, so it requires Go 1.17.13. + Go 1.20 looks for <code>$HOME/go1.17.13</code> or <code>$HOME/sdk/go1.17.13</code> + before falling back to <code>$HOME/go1.4</code> + (to support systems that hard-coded the path $HOME/go1.4 but have installed + a newer Go toolchain there). + In the future, we plan to move the bootstrap toolchain forward approximately once a year, + and in particular we expect that Go 1.22 will require the final point release of Go 1.20 for bootstrap. +</p> + +<h2 id="library">Core library</h2> + +<h3 id="crypto/ecdh">New crypto/ecdh package</h3> + +<p><!-- https://go.dev/issue/52221, CL 398914, CL 450335, https://go.dev/issue/56052 --> + Go 1.20 adds a new <a href="/pkg/crypto/ecdh/"><code>crypto/ecdh</code></a> package + to provide explicit support for Elliptic Curve Diffie-Hellman key exchanges + over NIST curves and Curve25519. +</p> +<p> + Programs should use <code>crypto/ecdh</code> instead of the lower-level functionality in + <a href="/pkg/crypto/elliptic/"><code>crypto/elliptic</code></a> for ECDH, and + third-party modules for more advanced use cases. +</p> + +<h3 id="errors">Wrapping multiple errors</h3> + +<p><!-- CL 432898 --> + Go 1.20 expands support for error wrapping to permit an error to + wrap multiple other errors. +</p> +<p> + An error <code>e</code> can wrap more than one error by providing + an <code>Unwrap</code> method that returns a <code>[]error</code>. +</p> +<p> + The <a href="/pkg/errors/#Is"><code>errors.Is</code></a> and + <a href="/pkg/errors/#As"><code>errors.As</code></a> functions + have been updated to inspect multiply wrapped errors. +</p> +<p> + The <a href="/pkg/fmt/#Errorf"><code>fmt.Errorf</code></a> function + now supports multiple occurrences of the <code>%w</code> format verb, + which will cause it to return an error that wraps all of those error operands. +</p> +<p> + The new function <a href="/pkg/errors/#Join"><code>errors.Join</code></a> + returns an error wrapping a list of errors. +</p> + +<h3 id="http_responsecontroller">HTTP ResponseController</h3> + +<p><!-- CL 436890, https://go.dev/issue/54136 --> + The new + <a href="/pkg/net/http/#ResponseController"><code>"net/http".ResponseController</code></a> + type provides access to extended per-request functionality not handled by the + <a href="/pkg/net/http/#ResponseWriter"><code>"net/http".ResponseWriter</code></a> interface. +</p> + +<p> + Previously, we have added new per-request functionality by defining optional + interfaces which a <code>ResponseWriter</code> can implement, such as + <a href="/pkg/net/http/#Flusher"><code>Flusher</code></a>. These interfaces + are not discoverable and clumsy to use. +</p> + +<p> + The <code>ResponseController</code> type provides a clearer, more discoverable way + to add per-handler controls. Two such controls also added in Go 1.20 are + <code>SetReadDeadline</code> and <code>SetWriteDeadline</code>, which allow setting + per-request read and write deadlines. For example: +</p> + +<pre> +func RequestHandler(w ResponseWriter, r *Request) { + rc := http.NewResponseController(w) + rc.SetWriteDeadline(time.Time{}) // disable Server.WriteTimeout when sending a large response + io.Copy(w, bigData) +} +</pre> + +<h3 id="reverseproxy_rewrite">New ReverseProxy Rewrite hook</h3> + +<p><!-- https://go.dev/issue/53002, CL 407214 --> + The <a href="/pkg/net/http/httputil/#ReverseProxy"><code>httputil.ReverseProxy</code></a> + forwarding proxy includes a new + <a href="/pkg/net/http/httputil/#ReverseProxy.Rewrite"><code>Rewrite</code></a> + hook function, superseding the + previous <code>Director</code> hook. +</p> + +<p> + The <code>Rewrite</code> hook accepts a + <a href="/pkg/net/http/httputil/#ProxyRequest"><code>ProxyRequest</code></a> parameter, + which includes both the inbound request received by the proxy and the outbound + request that it will send. + Unlike <code>Director</code> hooks, which only operate on the outbound request, + this permits <code>Rewrite</code> hooks to avoid certain scenarios where + a malicious inbound request may cause headers added by the hook + to be removed before forwarding. + See <a href="https://go.dev/issue/50580">issue #50580</a>. +</p> + +<p> + The <a href="/pkg/net/http/httputil/#ProxyRequest.SetURL"><code>ProxyRequest.SetURL</code></a> + method routes the outbound request to a provided destination + and supersedes the <code>NewSingleHostReverseProxy</code> function. + Unlike <code>NewSingleHostReverseProxy</code>, <code>SetURL</code> + also sets the <code>Host</code> header of the outbound request. +</p> + +<p><!-- https://go.dev/issue/50465, CL 407414 --> + The + <a href="/pkg/net/http/httputil/#ProxyRequest.SetXForwarded"><code>ProxyRequest.SetXForwarded</code></a> + method sets the <code>X-Forwarded-For</code>, <code>X-Forwarded-Host</code>, + and <code>X-Forwarded-Proto</code> headers of the outbound request. + When using a <code>Rewrite</code>, these headers are not added by default. +</p> + +<p> + An example of a <code>Rewrite</code> hook using these features is: +</p> + +<pre> +proxyHandler := &httputil.ReverseProxy{ + Rewrite: func(r *httputil.ProxyRequest) { + r.SetURL(outboundURL) // Forward request to outboundURL. + r.SetXForwarded() // Set X-Forwarded-* headers. + r.Out.Header.Set("X-Additional-Header", "header set by the proxy") + }, +} +</pre> + +<p><!-- CL 407375 --> + <a href="/pkg/net/http/httputil/#ReverseProxy"><code>ReverseProxy</code></a> no longer adds a <code>User-Agent</code> header + to forwarded requests when the incoming request does not have one. +</p> + +<h3 id="minor_library_changes">Minor changes to the library</h3> + +<p> + As always, there are various minor changes and updates to the library, + made with the Go 1 <a href="/doc/go1compat">promise of compatibility</a> + in mind. + There are also various performance improvements, not enumerated here. +</p> + +<dl id="archive/tar"><dt><a href="/pkg/archive/tar/">archive/tar</a></dt> + <dd> + <p><!-- https://go.dev/issue/55356, CL 449937 --> + When the <code>GODEBUG=tarinsecurepath=0</code> environment variable is set, + <a href="/pkg/archive/tar/#Reader.Next"><code>Reader.Next</code></a> method + will now return the error <a href="/pkg/archive/tar/#ErrInsecurePath"><code>ErrInsecurePath</code></a> + for an entry with a file name that is an absolute path, + refers to a location outside the current directory, contains invalid + characters, or (on Windows) is a reserved name such as <code>NUL</code>. + A future version of Go may disable insecure paths by default. + </p> + </dd> +</dl><!-- archive/tar --> + +<dl id="archive/zip"><dt><a href="/pkg/archive/zip/">archive/zip</a></dt> + <dd> + <p><!-- https://go.dev/issue/55356 --> + When the <code>GODEBUG=zipinsecurepath=0</code> environment variable is set, + <a href="/pkg/archive/zip/#NewReader"><code>NewReader</code></a> will now return the error + <a href="/pkg/archive/zip/#ErrInsecurePath"><code>ErrInsecurePath</code></a> + when opening an archive which contains any file name that is an absolute path, + refers to a location outside the current directory, contains invalid + characters, or (on Windows) is a reserved names such as <code>NUL</code>. + A future version of Go may disable insecure paths by default. + </p> + <p><!-- CL 449955 --> + Reading from a directory file that contains file data will now return an error. + The zip specification does not permit directory files to contain file data, + so this change only affects reading from invalid archives. + </p> + </dd> +</dl><!-- archive/zip --> + +<dl id="bytes"><dt><a href="/pkg/bytes/">bytes</a></dt> + <dd> + <p><!-- CL 407176 --> + The new + <a href="/pkg/bytes/#CutPrefix"><code>CutPrefix</code></a> and + <a href="/pkg/bytes/#CutSuffix"><code>CutSuffix</code></a> functions + are like <a href="/pkg/bytes/#TrimPrefix"><code>TrimPrefix</code></a> + and <a href="/pkg/bytes/#TrimSuffix"><code>TrimSuffix</code></a> + but also report whether the string was trimmed. + </p> + + <p><!-- CL 359675, https://go.dev/issue/45038 --> + The new <a href="/pkg/bytes/#Clone"><code>Clone</code></a> function + allocates a copy of a byte slice. + </p> + </dd> +</dl><!-- bytes --> + +<dl id="context"><dt><a href="/pkg/context/">context</a></dt> + <dd> + <p><!-- https://go.dev/issue/51365, CL 375977 --> + The new <a href="/pkg/context/#WithCancelCause"><code>WithCancelCause</code></a> function + provides a way to cancel a context with a given error. + That error can be retrieved by calling the new <a href="/pkg/context/#Cause"><code>Cause</code></a> function. + </p> + </dd> +</dl><!-- context --> + +<dl id="crypto/ecdsa"><dt><a href="/pkg/crypto/ecdsa/">crypto/ecdsa</a></dt> + <dd> + <p><!-- CL 353849 --> + When using supported curves, all operations are now implemented in constant time. + This led to an increase in CPU time between 5% and 30%, mostly affecting P-384 and P-521. + </p> + + <p><!-- https://go.dev/issue/56088, CL 450816 --> + The new <a href="/pkg/crypto/ecdsa/#PrivateKey.ECDH"><code>PrivateKey.ECDH</code></a> method + converts an <code>ecdsa.PrivateKey</code> to an <code>ecdh.PrivateKey</code>. + </p> + </dd> +</dl><!-- crypto/ecdsa --> + +<dl id="crypto/ed25519"><dt><a href="/pkg/crypto/ed25519/">crypto/ed25519</a></dt> + <dd> + <p><!-- CL 373076, CL 404274, https://go.dev/issue/31804 --> + The <a href="/pkg/crypto/ed25519/#PrivateKey.Sign"><code>PrivateKey.Sign</code></a> method + and the + <a href="/pkg/crypto/ed25519/#VerifyWithOptions"><code>VerifyWithOptions</code></a> function + now support signing pre-hashed messages with Ed25519ph, + indicated by an + <a href="/pkg/crypto/ed25519/#Options.HashFunc"><code>Options.HashFunc</code></a> + that returns + <a href="/pkg/crypto/#SHA512"><code>crypto.SHA512</code></a>. + They also now support Ed25519ctx and Ed25519ph with context, + indicated by setting the new + <a href="/pkg/crypto/ed25519/#Options.Context"><code>Options.Context</code></a> + field. + </p> + </dd> +</dl><!-- crypto/ed25519 --> + +<dl id="crypto/rsa"><dt><a href="/pkg/crypto/rsa/">crypto/rsa</a></dt> + <dd> + <p><!-- CL 418874, https://go.dev/issue/19974 --> + The new field <a href="/pkg/crypto/rsa/#OAEPOptions.MGFHash"><code>OAEPOptions.MGFHash</code></a> + allows configuring the MGF1 hash separately for OAEP decryption. + </p> + + <p><!-- https://go.dev/issue/20654 --> + crypto/rsa now uses a new, safer, constant-time backend. This causes a CPU + runtime increase for decryption operations between approximately 15% + (RSA-2048 on amd64) and 45% (RSA-4096 on arm64), and more on 32-bit architectures. + Encryption operations are approximately 20x slower than before (but still 5-10x faster than decryption). + Performance is expected to improve in future releases. + Programs must not modify or manually generate the fields of + <a href="/pkg/crypto/rsa/#PrecomputedValues"><code>PrecomputedValues</code></a>. + </p> + </dd> +</dl><!-- crypto/rsa --> + +<dl id="crypto/subtle"><dt><a href="/pkg/crypto/subtle/">crypto/subtle</a></dt> + <dd> + <p><!-- https://go.dev/issue/53021, CL 421435 --> + The new function <a href="/pkg/crypto/subtle/#XORBytes"><code>XORBytes</code></a> + XORs two byte slices together. + </p> + </dd> +</dl><!-- crypto/subtle --> + +<dl id="crypto/tls"><dt><a href="/pkg/crypto/tls/">crypto/tls</a></dt> + <dd> + <p><!-- CL 426455, CL 427155, CL 426454, https://go.dev/issue/46035 --> + Parsed certificates are now shared across all clients actively using that certificate. + The memory savings can be significant in programs that make many concurrent connections to a + server or collection of servers sharing any part of their certificate chains. + </p> + + <p><!-- https://go.dev/issue/48152, CL 449336 --> + For a handshake failure due to a certificate verification failure, + the TLS client and server now return an error of the new type + <a href="/pkg/crypto/tls/#CertificateVerificationError"><code>CertificateVerificationError</code></a>, + which includes the presented certificates. + </p> + </dd> +</dl><!-- crypto/tls --> + +<dl id="crypto/x509"><dt><a href="/pkg/crypto/x509/">crypto/x509</a></dt> + <dd> + <p><!-- CL 450816, CL 450815 --> + <a href="/pkg/crypto/x509/#ParsePKCS8PrivateKey"><code>ParsePKCS8PrivateKey</code></a> + and + <a href="/pkg/crypto/x509/#MarshalPKCS8PrivateKey"><code>MarshalPKCS8PrivateKey</code></a> + now support keys of type <a href="/pkg/crypto/ecdh.PrivateKey"><code>*crypto/ecdh.PrivateKey</code></a>. + <a href="/pkg/crypto/x509/#ParsePKIXPublicKey"><code>ParsePKIXPublicKey</code></a> + and + <a href="/pkg/crypto/x509/#MarshalPKIXPublicKey"><code>MarshalPKIXPublicKey</code></a> + now support keys of type <a href="/pkg/crypto/ecdh.PublicKey"><code>*crypto/ecdh.PublicKey</code></a>. + Parsing NIST curve keys still returns values of type + <code>*ecdsa.PublicKey</code> and <code>*ecdsa.PrivateKey</code>. + Use their new <code>ECDH</code> methods to convert to the <code>crypto/ecdh</code> types. + </p> + <p><!-- CL 449235 --> + The new <a href="/pkg/crypto/x509/#SetFallbackRoots"><code>SetFallbackRoots</code></a> + function allows a program to define a set of fallback root certificates in case an + operating system verifier or standard platform root bundle is unavailable at runtime. + It will most commonly be used with a new package, <a href="/pkg/golang.org/x/crypto/x509roots/fallback">golang.org/x/crypto/x509roots/fallback</a>, + which will provide an up to date root bundle. + </p> + </dd> +</dl><!-- crypto/x509 --> + +<dl id="debug/elf"><dt><a href="/pkg/debug/elf/">debug/elf</a></dt> + <dd> + <p><!-- CL 429601 --> + Attempts to read from a <code>SHT_NOBITS</code> section using + <a href="/pkg/debug/elf/#Section.Data"><code>Section.Data</code></a> + or the reader returned by <a href="/pkg/debug/elf/#Section.Open"><code>Section.Open</code></a> + now return an error. + </p> + <p><!-- CL 420982 --> + Additional <a href="/pkg/debug/elf/#R_LARCH"><code>R_LARCH_*</code></a> constants are defined for use with LoongArch systems. + </p> + <p><!-- CL 420982, CL 435415, CL 425555 --> + Additional <a href="/pkg/debug/elf/#R_PPC64"><code>R_PPC64_*</code></a> constants are defined for use with PPC64 ELFv2 relocations. + </p> + <p><!-- CL 411915 --> + The constant value for <a href="/pkg/debug/elf/#R_PPC64_SECTOFF_LO_DS"><code>R_PPC64_SECTOFF_LO_DS</code></a> is corrected, from 61 to 62. + </p> + </dd> +</dl><!-- debug/elf --> + +<dl id="debug/gosym"><dt><a href="/pkg/debug/gosym/">debug/gosym</a></dt> + <dd> + <p><!-- https://go.dev/issue/37762, CL 317917 --> + Due to a change of <a href="#linker">Go's symbol naming conventions</a>, tools that + process Go binaries should use Go 1.20's <code>debug/gosym</code> package to + transparently handle both old and new binaries. + </p> + </dd> +</dl><!-- debug/gosym --> + +<dl id="debug/pe"><dt><a href="/pkg/debug/pe/">debug/pe</a></dt> + <dd> + <p><!-- CL 421357 --> + Additional <a href="/pkg/debug/pe/#IMAGE_FILE_MACHINE_RISCV128"><code>IMAGE_FILE_MACHINE_RISCV*</code></a> constants are defined for use with RISC-V systems. + </p> + </dd> +</dl><!-- debug/pe --> + +<dl id="encoding/binary"><dt><a href="/pkg/encoding/binary/">encoding/binary</a></dt> + <dd> + <p><!-- CL 420274 --> + The <a href="/pkg/encoding/binary/#ReadVarint"><code>ReadVarint</code></a> and + <a href="/pkg/encoding/binary/#ReadUvarint"><code>ReadUvarint</code></a> + functions will now return <code>io.ErrUnexpectedEOF</code> after reading a partial value, + rather than <code>io.EOF</code>. + </p> + </dd> +</dl><!-- encoding/binary --> + +<dl id="encoding/xml"><dt><a href="/pkg/encoding/xml/">encoding/xml</a></dt> + <dd> + <p><!-- https://go.dev/issue/53346, CL 424777 --> + The new <a href="/pkg/encoding/xml/#Encoder.Close"><code>Encoder.Close</code></a> method + can be used to check for unclosed elements when finished encoding. + </p> + + <p><!-- CL 103875, CL 105636 --> + The decoder now rejects element and attribute names with more than one colon, + such as <code><a:b:c></code>, + as well as namespaces that resolve to an empty string, such as <code>xmlns:a=""</code>. + </p> + + <p><!-- CL 107255 --> + The decoder now rejects elements that use different namespace prefixes in the opening and closing tag, + even if those prefixes both denote the same namespace. + </p> + </dd> +</dl><!-- encoding/xml --> + +<dl id="errors"><dt><a href="/pkg/errors/">errors</a></dt> + <dd> + <p><!-- https://go.dev/issue/53435 --> + The new <a href="/pkg/errors/#Join"><code>Join</code></a> function returns an error wrapping a list of errors. + </p> + </dd> +</dl><!-- errors --> + +<dl id="fmt"><dt><a href="/pkg/fmt/">fmt</a></dt> + <dd> + <p><!-- https://go.dev/issue/53435 --> + The <a href="/pkg/fmt/#Errorf"><code>Errorf</code></a> function supports multiple occurrences of + the <code>%w</code> format verb, returning an error that unwraps to the list of all arguments to <code>%w</code>. + </p> + <p><!-- https://go.dev/issue/51668, CL 400875 --> + The new <a href="/pkg/fmt/#FormatString"><code>FormatString</code></a> function recovers the + formatting directive corresponding to a <a href="/pkg/fmt/#State"><code>State</code></a>, + which can be useful in <a href="/pkg/fmt/#Formatter"><code>Formatter</code></a>. + implementations. + </p> + </dd> +</dl><!-- fmt --> + +<dl id="go/ast"><dt><a href="/pkg/go/ast/">go/ast</a></dt> + <dd> + <p><!-- CL 426091, https://go.dev/issue/50429 --> + The new <a href="/pkg/go/ast/#RangeStmt.Range"><code>RangeStmt.Range</code></a> field + records the position of the <code>range</code> keyword in a range statement. + </p> + <p><!-- CL 427955, https://go.dev/issue/53202 --> + The new <a href="/pkg/go/ast/#File.FileStart"><code>File.FileStart</code></a> + and <a href="/pkg/go/ast/#File.FileEnd"><code>File.FileEnd</code></a> fields + record the position of the start and end of the entire source file. + </p> + </dd> +</dl><!-- go/ast --> + +<dl id="go/token"><dt><a href="/pkg/go/token/">go/token</a></dt> + <dd> + <p><!-- CL 410114, https://go.dev/issue/53200 --> + The new <a href="/pkg/go/token/#FileSet.RemoveFile"><code>FileSet.RemoveFile</code></a> method + removes a file from a <code>FileSet</code>. + Long-running programs can use this to release memory associated + with files they no longer need. + </p> + </dd> +</dl><!-- go/token --> + +<dl id="go/types"><dt><a href="/pkg/go/types/">go/types</a></dt> + <dd> + <p><!-- CL 454575 --> + The new <a href="/pkg/go/types/#Satisfies"><code>Satisfies</code></a> function reports + whether a type satisfies a constraint. + This change aligns with the <a href="#language">new language semantics</a> + that distinguish satisfying a constraint from implementing an interface. + </p> + </dd> +</dl><!-- go/types --> + +<dl id="io"><dt><a href="/pkg/io/">io</a></dt> + <dd> + <p><!-- https://go.dev/issue/45899, CL 406776 --> + The new <a href="/pkg/io/#OffsetWriter"><code>OffsetWriter</code></a> wraps an underlying + <a href="/pkg/io/#WriterAt"><code>WriterAt</code></a> + and provides <code>Seek</code>, <code>Write</code>, and <code>WriteAt</code> methods + that adjust their effective file offset position by a fixed amount. + </p> + </dd> +</dl><!-- io --> + +<dl id="io/fs"><dt><a href="/pkg/io/fs/">io/fs</a></dt> + <dd> + <p><!-- CL 363814, https://go.dev/issue/47209 --> + The new error <a href="/pkg/io/fs/#SkipAll"><code>SkipAll</code></a> + terminates a <a href="/pkg/io/fs/#WalkDir"><code>WalkDir</code></a> + immediately but successfully. + </p> + </dd> +</dl><!-- io --> + +<dl id="math/big"><dt><a href="/pkg/math/big/">math/big</a></dt> + <dd> + <p><!-- https://go.dev/issue/52182 --> + The <a href="/pkg/math/big/">math/big</a> package's wide scope and + input-dependent timing make it ill-suited for implementing cryptography. + The cryptography packages in the standard library no longer call non-trivial + <a href="/pkg/math/big#Int">Int</a> methods on attacker-controlled inputs. + In the future, the determination of whether a bug in math/big is + considered a security vulnerability will depend on its wider impact on the + standard library. + </p> + </dd> +</dl><!-- math/big --> + +<dl id="math/rand"><dt><a href="/pkg/math/rand/">math/rand</a></dt> + <dd> + <p><!-- https://go.dev/issue/54880, CL 436955, https://go.dev/issue/56319 --> + The <a href="/pkg/math/rand/">math/rand</a> package now automatically seeds + the global random number generator + (used by top-level functions like <code>Float64</code> and <code>Int</code>) with a random value, + and the top-level <a href="/pkg/math/rand/#Seed"><code>Seed</code></a> function has been deprecated. + Programs that need a reproducible sequence of random numbers + should prefer to allocate their own random source, using <code>rand.New(rand.NewSource(seed))</code>. + </p> + <p> + Programs that need the earlier consistent global seeding behavior can set + <code>GODEBUG=randautoseed=0</code> in their environment. + </p> + <p><!-- https://go.dev/issue/20661 --> + The top-level <a href="/pkg/math/rand/#Read"><code>Read</code></a> function has been deprecated. + In almost all cases, <a href="/pkg/crypto/rand/#Read"><code>crypto/rand.Read</code></a> is more appropriate. + </p> + </dd> +</dl><!-- math/rand --> + +<dl id="mime"><dt><a href="/pkg/mime/">mime</a></dt> + <dd> + <p><!-- https://go.dev/issue/48866 --> + The <a href="/pkg/mime/#ParseMediaType"><code>ParseMediaType</code></a> function now allows duplicate parameter names, + so long as the values of the names are the same. + </p> + </dd> +</dl><!-- mime --> + +<dl id="mime/multipart"><dt><a href="/pkg/mime/multipart/">mime/multipart</a></dt> + <dd> + <p><!-- CL 431675 --> + Methods of the <a href="/pkg/mime/multipart/#Reader"><code>Reader</code></a> type now wrap errors + returned by the underlying <code>io.Reader</code>. + </p> + </dd> +</dl><!-- mime/multipart --> + +<dl id="net"><dt><a href="/pkg/net/">net</a></dt> + <dd> + <p><!-- https://go.dev/issue/50101, CL 446179 --> + The <a href="/pkg/net/#LookupCNAME"><code>LookupCNAME</code></a> + function now consistently returns the contents + of a <code>CNAME</code> record when one exists. Previously on Unix systems and + when using the pure Go resolver, <code>LookupCNAME</code> would return an error + if a <code>CNAME</code> record referred to a name that with no <code>A</code>, + <code>AAAA</code>, or <code>CNAME</code> record. This change modifies + <code>LookupCNAME</code> to match the previous behavior on Windows, + allowing <code>LookupCNAME</code> to succeed whenever a + <code>CNAME</code> exists. + </p> + + <p><!-- https://go.dev/issue/53482, CL 413454 --> + <a href="/pkg/net/#Interface.Flags"><code>Interface.Flags</code></a> now includes the new flag <code>FlagRunning</code>, + indicating an operationally active interface. An interface which is administratively + configured but not active (for example, because the network cable is not connected) + will have <code>FlagUp</code> set but not <code>FlagRunning</code>. + </p> + + <p><!-- https://go.dev/issue/55301, CL 444955 --> + The new <a href="/pkg/net/#Dialer.ControlContext"><code>Dialer.ControlContext</code></a> field contains a callback function + similar to the existing <a href="/pkg/net/#Dialer.Control"><code>Dialer.Control</code></a> hook, that additionally + accepts the dial context as a parameter. + <code>Control</code> is ignored when <code>ControlContext</code> is not nil. + </p> + + <p><!-- CL 428955 --> + The Go DNS resolver recognizes the <code>trust-ad</code> resolver option. + When <code>options trust-ad</code> is set in <code>resolv.conf</code>, + the Go resolver will set the AD bit in DNS queries. The resolver does not + make use of the AD bit in responses. + </p> + + <p><!-- CL 448075 --> + DNS resolution will detect changes to <code>/etc/nsswitch.conf</code> + and reload the file when it changes. Checks are made at most once every + five seconds, matching the previous handling of <code>/etc/hosts</code> + and <code>/etc/resolv.conf</code>. + </p> + </dd> +</dl><!-- net --> + +<dl id="net/http"><dt><a href="/pkg/net/http/">net/http</a></dt> + <dd> + <p><!-- https://go.dev/issue/51914 --> + The <a href="/pkg/net/http/#ResponseWriter.WriteHeader"><code>ResponseWriter.WriteHeader</code></a> function now supports sending + <code>1xx</code> status codes. + </p> + + <p><!-- https://go.dev/issue/41773, CL 356410 --> + The new <a href="/pkg/net/http/#Server.DisableGeneralOptionsHandler"><code>Server.DisableGeneralOptionsHandler</code></a> configuration setting + allows disabling the default <code>OPTIONS *</code> handler. + </p> + + <p><!-- https://go.dev/issue/54299, CL 447216 --> + The new <a href="/pkg/net/http/#Transport.OnProxyConnectResponse"><code>Transport.OnProxyConnectResponse</code></a> hook is called + when a <code>Transport</code> receives an HTTP response from a proxy + for a <code>CONNECT</code> request. + </p> + + <p><!-- https://go.dev/issue/53960, CL 418614 --> + The HTTP server now accepts HEAD requests containing a body, + rather than rejecting them as invalid. + </p> + + <p><!-- https://go.dev/issue/53896 --> + HTTP/2 stream errors returned by <code>net/http</code> functions may be converted + to a <a href="/pkg/golang.org/x/net/http2/#StreamError"><code>golang.org/x/net/http2.StreamError</code></a> using + <a href="/pkg/errors/#As"><code>errors.As</code></a>. + </p> + + <p><!-- https://go.dev/cl/397734 --> + Leading and trailing spaces are trimmed from cookie names, + rather than being rejected as invalid. + For example, a cookie setting of "name =value" + is now accepted as setting the cookie "name". + </p> + </dd> +</dl><!-- net/http --> + +<dl id="net/netip"><dt><a href="/pkg/net/netip/">net/netip</a></dt> + <dd> + <p><!-- https://go.dev/issue/51766, https://go.dev/issue/51777, CL 412475 --> + The new <a href="/pkg/net/netip/#IPv6LinkLocalAllRouters"><code>IPv6LinkLocalAllRouters</code></a> + and <a href="/pkg/net/netip/#IPv6Loopback"><code>IPv6Loopback</code></a> functions + are the <code>net/netip</code> equivalents of + <a href="/pkg/net/#IPv6loopback"><code>net.IPv6loopback</code></a> and + <a href="/pkg/net/#IPv6linklocalallrouters"><code>net.IPv6linklocalallrouters</code></a>. + </p> + </dd> +</dl><!-- net/netip --> + +<dl id="os"><dt><a href="/pkg/os/">os</a></dt> + <dd> + <p><!-- CL 448897 --> + On Windows, the name <code>NUL</code> is no longer treated as a special case in + <a href="/pkg/os/#Mkdir"><code>Mkdir</code></a> and + <a href="/pkg/os/#Stat"><code>Stat</code></a>. + </p> + <p><!-- https://go.dev/issue/52747, CL 405275 --> + On Windows, <a href="/pkg/os/#File.Stat"><code>File.Stat</code></a> + now uses the file handle to retrieve attributes when the file is a directory. + Previously it would use the path passed to + <a href="/pkg/os/#Open"><code>Open</code></a>, which may no longer be the file + represented by the file handle if the file has been moved or replaced. + This change modifies <code>Open</code> to open directories without the + <code>FILE_SHARE_DELETE</code> access, which match the behavior of regular files. + </p> + <p><!-- https://go.dev/issue/36019, CL 405275 --> + On Windows, <a href="/pkg/os/#File.Seek"><code>File.Seek</code></a> now supports + seeking to the beginning of a directory. + </p> + </dd> +</dl><!-- os --> + +<dl id="os/exec"><dt><a href="/pkg/os/exec/">os/exec</a></dt> + <dd> + <p><!-- https://go.dev/issue/50436, CL 401835 --> + The new <a href="/pkg/os/exec/#Cmd"><code>Cmd</code></a> fields + <a href="/pkg/os/exec/#Cmd.Cancel"><code>Cancel</code></a> and + <a href="/pkg/os/exec/#Cmd.WaitDelay"><code>WaitDelay</code></a> + specify the behavior of the <code>Cmd</code> when its associated + <code>Context</code> is canceled or its process exits with I/O pipes still + held open by a child process. + </p> + </dd> +</dl><!-- os/exec --> + +<dl id="path/filepath"><dt><a href="/pkg/path/filepath/">path/filepath</a></dt> + <dd> + <p><!-- CL 363814, https://go.dev/issue/47209 --> + The new error <a href="/pkg/path/filepath/#SkipAll"><code>SkipAll</code></a> + terminates a <a href="/pkg/path/filepath/#Walk"><code>Walk</code></a> + immediately but successfully. + </p> + <p><!-- https://go.dev/issue/56219, CL 449239 --> + The new <a href="/pkg/path/filepath/#IsLocal"><code>IsLocal</code></a> function reports whether a path is + lexically local to a directory. + For example, if <code>IsLocal(p)</code> is <code>true</code>, + then <code>Open(p)</code> will refer to a file that is lexically + within the subtree rooted at the current directory. + </p> + </dd> +</dl><!-- io --> + +<dl id="reflect"><dt><a href="/pkg/reflect/">reflect</a></dt> + <dd> + <p><!-- https://go.dev/issue/46746, CL 423794 --> + The new <a href="/pkg/reflect/#Value.Comparable"><code>Value.Comparable</code></a> and + <a href="/pkg/reflect/#Value.Equal"><code>Value.Equal</code></a> methods + can be used to compare two <code>Value</code>s for equality. + <code>Comparable</code> reports whether <code>Equal</code> is a valid operation for a given <code>Value</code> receiver. + </p> + + <p><!-- https://go.dev/issue/48000, CL 389635 --> + The new <a href="/pkg/reflect/#Value.Grow"><code>Value.Grow</code></a> method + extends a slice to guarantee space for another <code>n</code> elements. + </p> + + <p><!-- https://go.dev/issue/52376, CL 411476 --> + The new <a href="/pkg/reflect/#Value.SetZero"><code>Value.SetZero</code></a> method + sets a value to be the zero value for its type. + </p> + + <p><!-- CL 425184 --> + Go 1.18 introduced <a href="/pkg/reflect/#Value.SetIterKey"><code>Value.SetIterKey</code></a> + and <a href="/pkg/reflect/#Value.SetIterValue"><code>Value.SetIterValue</code></a> methods. + These are optimizations: <code>v.SetIterKey(it)</code> is meant to be equivalent to <code>v.Set(it.Key())</code>. + The implementations incorrectly omitted a check for use of unexported fields that was present in the unoptimized forms. + Go 1.20 corrects these methods to include the unexported field check. + </p> + </dd> +</dl><!-- reflect --> + +<dl id="regexp"><dt><a href="/pkg/regexp/">regexp</a></dt> + <dd> + <p><!-- CL 444817 --> + Go 1.19.2 and Go 1.18.7 included a security fix to the regular expression parser, + making it reject very large expressions that would consume too much memory. + Because Go patch releases do not introduce new API, + the parser returned <a href="/pkg/regexp/syntax/#ErrInternalError"><code>syntax.ErrInternalError</code></a> in this case. + Go 1.20 adds a more specific error, <a href="/pkg/regexp/syntax/#ErrLarge"><code>syntax.ErrLarge</code></a>, + which the parser now returns instead. + </p> + </dd> +</dl><!-- regexp --> + +<dl id="runtime/cgo"><dt><a href="/pkg/runtime/cgo/">runtime/cgo</a></dt> + <dd> + <p><!-- https://go.dev/issue/46731, CL 421879 --> + Go 1.20 adds new <a href="/pkg/runtime/cgo/#Incomplete"><code>Incomplete</code></a> marker type. + Code generated by cgo will use <code>cgo.Incomplete</code> to mark an incomplete C type. + </p> + </dd> +</dl><!-- runtime/cgo --> + +<dl id="runtime/metrics"><dt><a href="/pkg/runtime/metrics/">runtime/metrics</a></dt> + <dd> + <p><!-- https://go.dev/issue/47216, https://go.dev/issue/49881 --> + Go 1.20 adds new <a href="/pkg/runtime/metrics/#hdr-Supported_metrics">supported metrics</a>, + including the current <code>GOMAXPROCS</code> setting (<code>/sched/gomaxprocs:threads</code>), + the number of cgo calls executed (<code>/cgo/go-to-c-calls:calls</code>), + total mutex block time (<code>/sync/mutex/wait/total</code>), and various measures of time + spent in garbage collection. + </p> + + <p><!-- CL 427615 --> + Time-based histogram metrics are now less precise, but take up much less memory. + </p> + </dd> +</dl><!-- runtime/metrics --> + +<dl id="runtime/pprof"><dt><a href="/pkg/runtime/pprof/">runtime/pprof</a></dt> + <dd> + <p><!-- CL 443056 --> + Mutex profile samples are now pre-scaled, fixing an issue where old mutex profile + samples would be scaled incorrectly if the sampling rate changed during execution. + </p> + + <p><!-- CL 416975 --> + Profiles collected on Windows now include memory mapping information that fixes + symbolization issues for position-independent binaries. + </p> + </dd> +</dl><!-- runtime/pprof --> + +<dl id="runtime/trace"><dt><a href="/pkg/runtime/trace/">runtime/trace</a></dt> + <dd> + <p><!-- CL 447135, https://go.dev/issue/55022 --> + The garbage collector's background sweeper now yields less frequently, + resulting in many fewer extraneous events in execution traces. + </p> + </dd> +</dl><!-- runtime/trace --> + +<dl id="strings"><dt><a href="/pkg/strings/">strings</a></dt> + <dd> + <p><!-- CL 407176, https://go.dev/issue/42537 --> + The new + <a href="/pkg/strings/#CutPrefix"><code>CutPrefix</code></a> and + <a href="/pkg/strings/#CutSuffix"><code>CutSuffix</code></a> functions + are like <a href="/pkg/strings/#TrimPrefix"><code>TrimPrefix</code></a> + and <a href="/pkg/strings/#TrimSuffix"><code>TrimSuffix</code></a> + but also report whether the string was trimmed. + </p> + + <p><!-- CL 359675, https://go.dev/issue/45038 --> + The new <a href="/pkg/strings/#Clone"><code>Clone</code></a> function + allocates a copy of a string. + </p> + </dd> +</dl><!-- strings --> + +<dl id="sync"><dt><a href="/pkg/sync/">sync</a></dt> + <dd> + <p><!-- CL 399094, https://go.dev/issue/51972 --> + The new <a href="/pkg/sync/#Map"><code>Map</code></a> methods <a href="/pkg/sync/#Map.Swap"><code>Swap</code></a>, + <a href="/pkg/sync/#Map.CompareAndSwap"><code>CompareAndSwap</code></a>, and + <a href="/pkg/sync/#Map.CompareAndDelete"><code>CompareAndDelete</code></a> + allow existing map entries to be updated atomically. + </p> + </dd> +</dl><!-- sync --> + +<dl id="syscall"><dt><a href="/pkg/syscall/">syscall</a></dt> + <dd> + <p><!-- CL 411596 --> + On FreeBSD, compatibility shims needed for FreeBSD 11 and earlier have been removed. + </p> + <p><!-- CL 407574 --> + On Linux, additional <a href="/pkg/syscall/#CLONE_CLEAR_SIGHAND"><code>CLONE_*</code></a> constants + are defined for use with the <a href="/pkg/syscall/#SysProcAttr.Cloneflags"><code>SysProcAttr.Cloneflags</code></a> field. + </p> + <p><!-- CL 417695 --> + On Linux, the new <a href="/pkg/syscall/#SysProcAttr.CgroupFD"><code>SysProcAttr.CgroupFD</code></a> + and <a href="/pkg/syscall/#SysProcAttr.UseCgroupFD"><code>SysProcAttr.UseCgroupFD</code></a> fields + provide a way to place a child process into a specific cgroup. + </p> + </dd> +</dl><!-- syscall --> + +<dl id="testing"><dt><a href="/pkg/testing/">testing</a></dt> + <dd> + <p><!-- https://go.dev/issue/43620, CL 420254 --> + The new method <a href="/pkg/testing/#B.Elapsed"><code>B.Elapsed</code></a> + reports the current elapsed time of the benchmark, which may be useful for + calculating rates to report with <code>ReportMetric</code>. + </p> + </dd> +</dl><!-- testing --> + +<dl id="time"><dt><a href="/pkg/time/">time</a></dt> + <dd> + <p><!-- https://go.dev/issue/52746, CL 412495 --> + The new time layout constants <a href="/pkg/time/#DateTime"><code>DateTime</code></a>, + <a href="/pkg/time/#DateOnly"><code>DateOnly</code></a>, and + <a href="/pkg/time/#TimeOnly"><code>TimeOnly</code></a> + provide names for three of the most common layout strings used in a survey of public Go source code. + </p> + + <p><!-- CL 382734, https://go.dev/issue/50770 --> + The new <a href="/pkg/time/#Time.Compare"><code>Time.Compare</code></a> method + compares two times. + </p> + + <p><!-- CL 425037 --> + <a href="/pkg/time/#Parse"><code>Parse</code></a> + now ignores sub-nanosecond precision in its input, + instead of reporting those digits as an error. + </p> + + <p><!-- CL 444277 --> + The <a href="/pkg/time/#Time.MarshalJSON"><code>Time.MarshalJSON</code></a> method + is now more strict about adherence to RFC 3339. + </p> + </dd> +</dl><!-- time --> + +<dl id="unicode/utf16"><dt><a href="/pkg/unicode/utf16/">unicode/utf16</a></dt> + <dd> + <p><!-- https://go.dev/issue/51896, CL 409054 --> + The new <a href="/pkg/unicode/utf16/#AppendRune"><code>AppendRune</code></a> + function appends the UTF-16 encoding of a given rune to a uint16 slice, + analogous to <a href="/pkg/unicode/utf8/#AppendRune"><code>utf8.AppendRune</code></a>. + </p> + </dd> +</dl><!-- unicode/utf16 --> + +<!-- Silence false positives from x/build/cmd/relnote: --> +<!-- https://go.dev/issue/45964 was documented in Go 1.18 release notes but closed recently --> +<!-- https://go.dev/issue/52114 is an accepted proposal to add golang.org/x/net/http2.Transport.DialTLSContext; it's not a part of the Go release --> +<!-- CL 431335: cmd/api: make check pickier about api/*.txt --> +<!-- CL 447896 api: add newline to 55301.txt; modified api/next/55301.txt --> +<!-- CL 449215 api/next/54299: add missing newline; modified api/next/54299.txt --> +<!-- CL 433057 cmd: update vendored golang.org/x/tools for multiple error wrapping --> +<!-- CL 423362 crypto/internal/boring: update to newer boringcrypto, add arm64 --> +<!-- https://go.dev/issue/53481 x/cryptobyte ReadUint64, AddUint64 --> +<!-- https://go.dev/issue/51994 x/crypto/ssh --> +<!-- https://go.dev/issue/55358 x/exp/slices --> +<!-- https://go.dev/issue/54714 x/sys/unix --> +<!-- https://go.dev/issue/50035 https://go.dev/issue/54237 x/time/rate --> +<!-- CL 345488 strconv optimization --> +<!-- CL 428757 reflect deprecation, rolled back --> +<!-- https://go.dev/issue/49390 compile -l -N is fully supported --> +<!-- https://go.dev/issue/54619 x/tools --> +<!-- CL 448898 reverted --> +<!-- https://go.dev/issue/54850 x/net/http2 Transport.MaxReadFrameSize --> +<!-- https://go.dev/issue/56054 x/net/http2 SETTINGS_HEADER_TABLE_SIZE --> +<!-- CL 450375 reverted --> +<!-- CL 453259 tracking deprecations in api --> +<!-- CL 453260 tracking darwin port in api --> +<!-- CL 453615 fix deprecation comment in archive/tar --> +<!-- CL 453616 fix deprecation comment in archive/zip --> +<!-- CL 453617 fix deprecation comment in encoding/csv --> +<!-- https://go.dev/issue/54661 x/tools/go/analysis --> +<!-- CL 423359, https://go.dev/issue/51317 arena --> |