| <!--{ |
| "Title": "Go 1.19 Release Notes", |
| "Path": "/doc/go1.19" |
| }--> |
| <!-- |
| 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 1.19</h2> |
| <p> |
| <strong> |
| Go 1.19 is not yet released. These are work-in-progress |
| release notes. Go 1.19 is expected to be released in August 2022. |
| </strong> |
| </p> |
| |
| <h2 id="language">Changes to the language</h2> |
| |
| <p><!-- https://go.dev/issue/52038 --> |
| There is only one small change to the language, |
| a <a href="https://github.com/golang/go/issues/52038">very small correction</a> |
| to the <a href="/ref/spec#Declarations_and_scope">scope of type parameters in method declarations</a>. |
| Existing programs are unaffected. |
| </p> |
| |
| <h2 id="mem">Memory Model</h2> |
| |
| <p><!-- https://go.dev/issue/50859 --> |
| The <a href="/ref/mem">Go memory model</a> has been revised to align Go with |
| the memory model used by C, C++, Java, JavaScript, Rust, and Swift. |
| Go only provides sequentially consistent atomics, not any of the more relaxed forms found in other languages. |
| Along with the memory model update, |
| Go 1.19 introduces <a href="#atomic_types">new types in the <code>sync/atomic</code> package</a> |
| that make it easier to use atomic values, such as |
| <a href="/pkg/sync/atomic/#Int64">atomic.Int64</a> |
| and |
| <a href="/pkg/sync/atomic/#Pointer">atomic.Pointer[T]</a>. |
| </p> |
| |
| <h2 id="ports">Ports</h2> |
| |
| <h3 id="loong64">Loongson 64-bit</h3> |
| <p><!-- https://go.dev/issue/46229 --> |
| Go 1.19 adds support for the Loongson 64-bit architecture LoongArch |
| on Linux (<code>GOOS=linux</code>, <code>GOARCH=loong64</code>). |
| </p> |
| |
| <h3 id="riscv64">RISC-V</h3> |
| <p><!-- CL 402374 --> |
| The <code>riscv64</code> port now supports passing function arguments |
| and result using registers. Benchmarking shows typical performance |
| improvements of 10% or more on <code>riscv64</code>. |
| </p> |
| |
| <h2 id="tools">Tools</h2> |
| |
| <h3 id="go-doc">Doc Comments</h3> |
| |
| <p><!-- https://go.dev/issue/51082 --><!-- CL 384265, CL 397276, CL 397278, CL 397279, CL 397281, CL 397284 --> |
| Go 1.19 adds support for links, lists, and clearer headings in doc comments. |
| As part of this change, <a href="/cmd/gofmt"><code>gofmt</code></a> |
| now reformats doc comments to make their rendered meaning clearer. |
| See “<a href="/doc/comment">Go Doc Comments</a>” |
| for syntax details and descriptions of common mistakes now highlighted by <code>gofmt</code>. |
| As another part of this change, the new package <a href="/pkg/go/doc/comment">go/doc/comment</a> |
| provides parsing and reformatting of doc comments |
| as well as support for rendering them to HTML, Markdown, and text. |
| </p> |
| |
| <h3 id="go-unix">New <code>unix</code> build constraint</h3> |
| |
| <p><!-- CL 389934 --><!-- https://go.dev/issue/20322 --><!-- https://go.dev/issue/51572 --> |
| The build constraint <code>unix</code> is now recognized |
| in <code>//go:build</code> lines. The constraint is satisfied |
| if the target operating system, also known as <code>GOOS</code>, is |
| a Unix or Unix-like system. For the 1.19 release it is satisfied |
| if <code>GOOS</code> is one of |
| <code>aix</code>, <code>android</code>, <code>darwin</code>, |
| <code>dragonfly</code>, <code>freebsd</code>, <code>hurd</code>, |
| <code>illumos</code>, <code>ios</code>, <code>linux</code>, |
| <code>netbsd</code>, <code>openbsd</code>, or <code>solaris</code>. |
| In future releases the <code>unix</code> constraint may match |
| additional newly supported operating systems. |
| </p> |
| |
| <h3 id="go-command">Go command</h3> |
| |
| <!-- https://go.dev/issue/51461 --> |
| <p> |
| The <code>-trimpath</code> flag, if set, is now included in the build settings |
| stamped into Go binaries by <code>go</code> <code>build</code>, and can be |
| examined using |
| <a href="https://pkg.go.dev/cmd/go#hdr-Print_Go_version"><code>go</code> <code>version</code> <code>-m</code></a> |
| or <a href="https://pkg.go.dev/runtime/debug#ReadBuildInfo"><code>debug.ReadBuildInfo</code></a>. |
| </p> |
| <p> |
| <code>go</code> <code>generate</code> now sets the <code>GOROOT</code> |
| environment variable explicitly in the generator's environment, so that |
| generators can locate the correct <code>GOROOT</code> even if built |
| with <code>-trimpath</code>. |
| </p> |
| |
| <p><!-- CL 404134 --> |
| <code>go</code> <code>test</code> and <code>go</code> <code>generate</code> now place |
| <code>GOROOT/bin</code> at the beginning of the <code>PATH</code> used for the |
| subprocess, so tests and generators that execute the <code>go</code> command |
| will resolve it to same <code>GOROOT</code>. |
| </p> |
| |
| <p><!-- CL 398058 --> |
| <code>go</code> <code>env</code> now quotes entries that contain spaces in |
| the <code>CGO_CFLAGS</code>, <code>CGO_CPPFLAGS</code>, <code>CGO_CXXFLAGS</code>, <code>CGO_FFLAGS</code>, <code>CGO_LDFLAGS</code>, |
| and <code>GOGCCFLAGS</code> variables it reports. |
| </p> |
| |
| <p><!-- CL 410821 --> |
| The <code>go</code> command now caches information necessary to load some modules, |
| which should result in a speed-up of some <code>go</code> <code>list</code> invocations. |
| </p> |
| |
| <h3 id="vet">Vet</h3> |
| |
| <p><!-- https://go.dev/issue/47528 --> |
| The <code>vet</code> checker “errorsas” now reports when |
| <a href="/pkg/errors/#As"><code>errors.As</code></a> is called |
| with a second argument of type <code>*error</code>, |
| a common mistake. |
| </p> |
| |
| <h2 id="runtime">Runtime</h2> |
| |
| <p><!-- https://go.dev/issue/48409 --><!-- CL 397018 --> |
| The runtime now includes support for a soft memory limit. This memory limit |
| includes the Go heap and all other memory managed by the runtime, and |
| excludes external memory sources such as mappings of the binary itself, |
| memory managed in other languages, and memory held by the operating system on |
| behalf of the Go program. This limit may be managed via |
| <a href="/pkg/runtime/debug/#SetMemoryLimit"><code>runtime/debug.SetMemoryLimit</code></a> |
| or the equivalent |
| <a href="/pkg/runtime/#hdr-Environment_Variables"><code>GOMEMLIMIT</code></a> |
| environment variable. The limit works in conjunction with |
| <a href="/pkg/runtime/debug/#SetGCPercent"><code>runtime/debug.SetGCPercent</code></a> |
| / <a href="/pkg/runtime/#hdr-Environment_Variables"><code>GOGC</code></a>, |
| and will be respected even if <code>GOGC=off</code>, allowing Go programs to |
| always make maximal use of their memory limit, improving resource efficiency |
| in some cases. See <a href="/doc/gc-guide">the GC guide</a> for |
| a detailed guide explaining the soft memory limit in more detail, as well as |
| a variety of common use-cases and scenarios. Please note that small memory |
| limits, on the order of tens of megabytes or less, are less likely to be |
| respected due to external latency factors, such as OS scheduling. See |
| <a href="https://go.dev/issue/52433">issue 52433</a> for more details. Larger |
| memory limits, on the order of hundreds of megabytes or more, are stable and |
| production-ready. |
| </p> |
| |
| <p><!-- CL 353989 --> |
| In order to limit the effects of GC thrashing when the program's live heap |
| size approaches the soft memory limit, the Go runtime also attempts to limit |
| total GC CPU utilization to 50%, excluding idle time, choosing to use more |
| memory over preventing application progress. In practice, we expect this limit |
| to only play a role in exceptional cases, and the new |
| <a href="/pkg/runtime/metrics/#hdr-Supported_metrics">runtime metric</a> |
| <code>/gc/limiter/last-enabled:gc-cycle</code> reports when this last |
| occurred. |
| </p> |
| |
| <p><!-- https://go.dev/issue/44163 --> |
| The runtime now schedules many fewer GC worker goroutines on idle operating |
| system threads when the application is idle enough to force a periodic GC |
| cycle. |
| </p> |
| |
| <p><!-- https://go.dev/issue/18138 --><!-- CL 345889 --> |
| The runtime will now allocate initial goroutine stacks based on the historic |
| average stack usage of goroutines. This avoids some of the early stack growth |
| and copying needed in the average case in exchange for at most 2x wasted |
| space on below-average goroutines. |
| </p> |
| |
| <p><!-- https://go.dev/issue/46279 --><!-- CL 393354 --><!-- CL 392415 --> |
| On Unix operating systems, Go programs that import package |
| <a href="/pkg/os/">os</a> now automatically increase the open file limit |
| (<code>RLIMIT_NOFILE</code>) to the maximum allowed value; |
| that is, they change the soft limit to match the hard limit. |
| This corrects artificially low limits set on some systems for compatibility with very old C programs using the |
| <a href="https://en.wikipedia.org/wiki/Select_(Unix)"><i>select</i></a> system call. |
| Go programs are not helped by that limit, and instead even simple programs like <code>gofmt</code> |
| often ran out of file descriptors on such systems when processing many files in parallel. |
| One impact of this change is that Go programs that in turn execute very old C programs in child processes |
| may run those programs with too high a limit. |
| This can be corrected by setting the hard limit before invoking the Go program. |
| </p> |
| |
| <p><!-- https://go.dev/issue/51485 --><!-- CL 390421 --> |
| Unrecoverable fatal errors (such as concurrent map writes, or unlock of |
| unlocked mutexes) now print a simpler traceback excluding runtime metadata |
| (equivalent to a fatal panic) unless <code>GOTRACEBACK=system</code> or |
| <code>crash</code>. Runtime-internal fatal error tracebacks always include |
| full metadata regardless of the value of <code>GOTRACEBACK</code> |
| </p> |
| |
| <p><!-- https://go.dev/issue/50614 --><!-- CL 395754 --> |
| Support for debugger-injected function calls has been added on ARM64, |
| enabling users to call functions from their binary in an interactive |
| debugging session when using a debugger that is updated to make use of this |
| functionality. |
| </p> |
| |
| <p><!-- https://go.dev/issue/44853 --> |
| The <a href="/doc/go1.18#go-build-asan">address sanitizer support added in Go 1.18</a> |
| now handles function arguments and global variables more precisely. |
| </p> |
| |
| <h2 id="compiler">Compiler</h2> |
| |
| <p><!-- https://go.dev/issue/5496 --><!-- CL 357330, 395714, 403979 --> |
| The compiler now uses |
| a <a href="https://en.wikipedia.org/wiki/Branch_table">jump |
| table</a> to implement large integer and string switch statements. |
| Performance improvements for the switch statement vary but can be |
| on the order of 20% faster. |
| (<code>GOARCH=amd64</code> and <code>GOARCH=arm64</code> only) |
| </p> |
| <p><!-- CL 391014 --> |
| The Go compiler now requires the <code>-p=importpath</code> flag to |
| build a linkable object file. This is already supplied by |
| the <code>go</code> command and by Bazel. Any other build systems |
| that invoke the Go compiler directly will need to make sure they |
| pass this flag as well. |
| </p> |
| |
| <h2 id="assembler">Assembler</h2> |
| <p><!-- CL 404298 --> |
| Like the compiler, the assembler now requires the |
| <code>-p=importpath</code> flag to build a linkable object file. |
| This is already supplied by the <code>go</code> command. Any other |
| build systems that invoke the Go assembler directly will need to |
| make sure they pass this flag as well. |
| </p> |
| |
| <h2 id="linker">Linker</h2> |
| <p><!-- https://go.dev/issue/50796, CL 380755 --> |
| On ELF platforms, the linker now emits compressed DWARF sections in |
| the standard gABI format (<code>SHF_COMPRESSED</code>), instead of |
| the legacy <code>.zdebug</code> format. |
| </p> |
| |
| <h2 id="library">Core library</h2> |
| |
| <h3 id="atomic_types">New atomic types</h3> |
| |
| <p><!-- https://go.dev/issue/50860 --><!-- CL 381317 --> |
| The <a href="/pkg/sync/atomic/"><code>sync/atomic</code></a> package defines new atomic types |
| <a href="/pkg/sync/atomic/#Bool"><code>Bool</code></a>, |
| <a href="/pkg/sync/atomic/#Int32"><code>Int32</code></a>, |
| <a href="/pkg/sync/atomic/#Int64"><code>Int64</code></a>, |
| <a href="/pkg/sync/atomic/#Uint32"><code>Uint32</code></a>, |
| <a href="/pkg/sync/atomic/#Uint64"><code>Uint64</code></a>, |
| <a href="/pkg/sync/atomic/#Uintptr"><code>Uintptr</code></a>, and |
| <a href="/pkg/sync/atomic/#Pointer"><code>Pointer</code></a>. |
| These types hide the underlying values so that all accesses are forced to use |
| the atomic APIs. |
| <a href="/pkg/sync/atomic/#Pointer"><code>Pointer</code></a> also avoids |
| the need to convert to |
| <a href="/pkg/unsafe/#Pointer"><code>unsafe.Pointer</code></a> at call sites. |
| <a href="/pkg/sync/atomic/#Int64"><code>Int64</code></a> and |
| <a href="/pkg/sync/atomic/#Uint64"><code>Uint64</code></a> are |
| automatically aligned to 64-bit boundaries in structs and allocated data, |
| even on 32-bit systems. |
| </p> |
| |
| <h3 id="os-exec-path">PATH lookups</h3> |
| |
| <p><!-- https://go.dev/issue/43724 --> |
| <!-- CL 381374 --><!-- CL 403274 --> |
| <a href="/pkg/os/exec/#Command"><code>Command</code></a> and |
| <a href="/pkg/os/exec/#LookPath"><code>LookPath</code></a> no longer |
| allow results from a PATH search to be found relative to the current directory. |
| This removes a <a href="/blog/path-security">common source of security problems</a> |
| but may also break existing programs that depend on using, say, <code>exec.Command("prog")</code> |
| to run a binary named <code>prog</code> (or, on Windows, <code>prog.exe</code>) in the current directory. |
| See the <a href="/pkg/os/exec/"><code>os/exec</code></a> package documentation for |
| information about how best to update such programs. |
| </p> |
| |
| <p><!-- https://go.dev/issue/43947 --> |
| On Windows, <code>Command</code> and <code>LookPath</code> now respect the |
| <a href="https://docs.microsoft.com/en-us/windows/win32/api/processenv/nf-processenv-needcurrentdirectoryforexepatha"><code>NoDefaultCurrentDirectoryInExePath</code></a> |
| environment variable, making it possible to disable |
| the default implicit search of “<code>.</code>” in PATH lookups on Windows systems. |
| </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/zip"><dt><a href="/pkg/archive/zip/">archive/zip</a></dt> |
| <dd> |
| <p><!-- CL 387976 --> |
| <a href="/pkg/archive/zip/#Reader"><code>Reader</code></a> |
| now ignores non-ZIP data at the start of a ZIP file, matching most other implementations. |
| This is necessary to read some Java JAR files, among other uses. |
| </p> |
| </dd> |
| </dl><!-- archive/zip --> |
| |
| <dl id="crypto/rand"><dt><a href="/pkg/crypto/rand/">crypto/rand</a></dt> |
| <dd> |
| <p><!-- CL 370894 --><!-- CL 390038 --> |
| <a href="/pkg/crypto/rand/#Read"><code>Read</code></a> no longer buffers |
| random data obtained from the operating system between calls. |
| </p> |
| |
| <p><!-- CL 375215 --> |
| On Plan 9, <code>Read</code> has been reimplemented, replacing the ANSI |
| X9.31 algorithm with fast key erasure. |
| </p> |
| </dd> |
| </dl><!-- crypto/rand --> |
| |
| <dl id="crypto/tls"><dt><a href="/pkg/crypto/tls/">crypto/tls</a></dt> |
| <dd> |
| <p><!-- CL 400974 --><!-- https://go.dev/issue/45428 --> |
| The <code>tls10default</code> <code>GODEBUG</code> option has been |
| removed. It is still possible to enable TLS 1.0 client-side by setting |
| <a href="/pkg/crypto/tls#Config.MinVersion"><code>Config.MinVersion</code></a>. |
| </p> |
| |
| <p><!-- CL 384894 --> |
| The TLS server and client now reject duplicate extensions in TLS |
| handshakes, as required by RFC 5246, Section 7.4.1.4 and RFC 8446, Section |
| 4.2. |
| </p> |
| </dd> |
| </dl><!-- crypto/tls --> |
| |
| <dl id="crypto/x509"><dt><a href="/pkg/crypto/x509/">crypto/x509</a></dt> |
| <dd> |
| <p><!-- CL 285872 --> |
| <a href="/pkg/crypto/x509/#CreateCertificate"><code>CreateCertificate</code></a> |
| no longer supports creating certificates with <code>SignatureAlgorithm</code> |
| set to <code>MD5WithRSA</code>. |
| </p> |
| |
| <p><!-- CL 400494 --> |
| <code>CreateCertificate</code> no longer accepts negative serial numbers. |
| </p> |
| |
| <p><!-- CL 383215 --> |
| <a href="/pkg/crypto/x509/#ParseCertificate"><code>ParseCertificate</code></a> |
| and <a href="/pkg/crypto/x509/#ParseCertificateRequest"><code>ParseCertificateRequest</code></a> |
| now reject certificates and CSRs which contain duplicate extensions. |
| </p> |
| |
| <p><!-- https://go.dev/issue/46057 --><!-- https://go.dev/issue/35044 --><!-- CL 398237 --><!-- CL 400175 --><!-- CL 388915 --> |
| The new <a href="/pkg/crypto/x509/#CertPool.Clone"><code>CertPool.Clone</code></a> |
| and <a href="/pkg/crypto/x509/#CertPool.Equal"><code>CertPool.Equal</code></a> |
| methods allow cloning a <code>CertPool</code> and checking the equality of two |
| <code>CertPool</code>s respectively. |
| </p> |
| |
| <p><!-- https://go.dev/issue/50674 --><!-- CL 390834 --> |
| The new function <a href="/pkg/crypto/x509/#ParseRevocationList"><code>ParseRevocationList</code></a> |
| provides a faster, safer to use CRL parser which returns a |
| <a href="/pkg/crypto/x509/#RevocationList"><code>RevocationList</code></a>. |
| To support this addition, <code>RevocationList</code> adds new fields |
| <code>RawIssuer</code>, <code>Signature</code>, |
| <code>AuthorityKeyId</code>, and <code>Extensions</code>. |
| |
| The new method <a href="/pkg/crypto/x509/#RevocationList.CheckSignatureFrom"><code>RevocationList.CheckSignatureFrom</code></a> |
| checks that the signature on a CRL is a valid signature from a |
| <a href="/pkg/crypto/x509/#Certificate"><code>Certificate</code></a>. |
| |
| With the new CRL functionality, the existing functions |
| <a href="/pkg/crypto/x509/#ParseCRL"><code>ParseCRL</code></a> and |
| <a href="/pkg/crypto/x509/#ParseDERCRL"><code>ParseDERCRL</code></a> are deprecated. |
| Additionally the method <a href="/pkg/crypto/x509#Certificate.CheckCRLSignature"><code>Certificate.CheckCRLSignature</code></a> |
| is deprecated. |
| </p> |
| |
| <p><!-- CL 389555 --> |
| When building paths, <a href="/pkg/crypto/x509/#Certificate.Verify"><code>Certificate.Verify</code></a> |
| now considers certificates to be equal when the subjects, public keys, and SANs |
| are all equal. Before, it required byte-for-byte equality. |
| </p> |
| </dd> |
| </dl><!-- crypto/x509 --> |
| |
| <dl id="crypto/x509/pkix"><dt><a href="/pkg/crypto/x509/pkix">crypto/x509/pkix</a></dt> |
| <dd> |
| <p><!-- CL 390834 --> |
| The types <a href="/pkg/crypto/x509/pkix#CertificateList"><code>CertificateList</code></a> and |
| <a href="/pkg/crypto/x509/pkix#TBSCertificateList"><code>TBSCertificateList</code></a> |
| have been deprecated. The new <a href="#crypto/x509"><code>crypto/x509</code> CRL functionality</a> |
| should be used instead. |
| </p> |
| </dd> |
| </dl><!-- crypto/x509/pkix --> |
| |
| <dl id="debug"><dt><a href="/pkg/debug/">debug</a></dt> |
| <dd> |
| <p><!-- CL 396735 --> |
| The new <code>EM_LONGARCH</code> and <code>R_LARCH_*</code> constants |
| support the loong64 port. |
| </p> |
| </dd> |
| </dl><!-- debug --> |
| |
| <dl id="debug/pe"><dt><a href="/pkg/debug/pe/">debug/pe</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/51868 --><!-- CL 394534 --> |
| The new <a href="/pkg/debug/pe/#File.COFFSymbolReadSectionDefAux"><code>File.COFFSymbolReadSectionDefAux</code></a> |
| method, which returns a <a href="/pkg/debug/pe/#COFFSymbolAuxFormat5"><code>COFFSymbolAuxFormat5</code></a>, |
| provides access to COMDAT information in PE file sections. |
| These are supported by new <code>IMAGE_COMDAT_*</code> and <code>IMAGE_SCN_*</code> constants. |
| </p> |
| </dd> |
| </dl><!-- debug/pe --> |
| |
| <dl id="encoding/binary"><dt><a href="/pkg/encoding/binary/">encoding/binary</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/50601 --><!-- CL 386017 --><!-- CL 389636 --> |
| The new interface |
| <a href="/pkg/encoding/binary/#AppendByteOrder"><code>AppendByteOrder</code></a> |
| provides efficient methods for appending a <code>uint16</code>, <code>uint32</code>, or <code>uint64</code> |
| to a byte slice. |
| <a href="/pkg/encoding/binary/#BigEndian"><code>BigEndian</code></a> and |
| <a href="/pkg/encoding/binary/#LittleEndian"><code>LittleEndian</code></a> now implement this interface. |
| </p> |
| <p><!-- https://go.dev/issue/51644 --><!-- CL 400176 --> |
| Similarly, the new functions |
| <a href="/pkg/encoding/binary/#AppendUvarint"><code>AppendUvarint</code></a> and |
| <a href="/pkg/encoding/binary/#AppendVarint"><code>AppendVarint</code></a> |
| are efficient appending versions of |
| <a href="/pkg/encoding/binary/#PutUvarint"><code>PutUvarint</code></a> and |
| <a href="/pkg/encoding/binary/#PutVarint"><code>PutVarint</code></a>. |
| </p> |
| </dd> |
| </dl><!-- encoding/binary --> |
| |
| <dl id="encoding/csv"><dt><a href="/pkg/encoding/csv/">encoding/csv</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/43401 --><!-- CL 405675 --> |
| The new method |
| <a href="/pkg/encoding/csv/#Reader.InputOffset"><code>Reader.InputOffset</code></a> |
| reports the reader's current input position as a byte offset, |
| analogous to <code>encoding/json</code>'s |
| <a href="/pkg/encoding/json/#Decoder.InputOffset"><code>Decoder.InputOffset</code></a>. |
| </p> |
| </dd> |
| </dl><!-- encoding/csv --> |
| |
| <dl id="encoding/xml"><dt><a href="/pkg/encoding/xml/">encoding/xml</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/45628 --><!-- CL 311270 --> |
| The new method |
| <a href="/pkg/encoding/xml/#Decoder.InputPos"><code>Decoder.InputPos</code></a> |
| reports the reader's current input position as a line and column, |
| analogous to <code>encoding/csv</code>'s |
| <a href="/pkg/encoding/csv/#Decoder.FieldPos"><code>Decoder.FieldPos</code></a>. |
| </p> |
| </dd> |
| </dl><!-- encoding/xml --> |
| |
| <dl id="flag"><dt><a href="/pkg/flag/">flag</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/45754 --><!-- CL 313329 --> |
| The new function |
| <a href="/pkg/flag/#TextVar"><code>TextVar</code></a> |
| defines a flag with a value implementing |
| <a href="/pkg/encoding/#TextUnmarshaler"><code>encoding.TextUnmarshaler</code></a>, |
| allowing command-line flag variables to have types such as |
| <a href="/pkg/math/big/#Int"><code>big.Int</code></a>, |
| <a href="/pkg/net/netip/#Addr"><code>netip.Addr</code></a>, and |
| <a href="/pkg/time/#Time"><code>time.Time</code></a>. |
| </p> |
| </dd> |
| </dl><!-- flag --> |
| |
| <dl id="fmt"><dt><a href="/pkg/fmt/">fmt</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/47579 --><!-- CL 406177 --> |
| The new functions |
| <a href="/pkg/fmt/#Append"><code>Append</code></a>, |
| <a href="/pkg/fmt/#Appendf"><code>Appendf</code></a>, and |
| <a href="/pkg/fmt/#Appendln"><code>Appendln</code></a> |
| append formatted data to byte slices. |
| </p> |
| </dd> |
| </dl><!-- fmt --> |
| |
| <dl id="go/parser"><dt><a href="/pkg/go/parser/">go/parser</a></dt> |
| <dd> |
| <p><!-- CL 403696 --> |
| The parser now recognizes <code>~x</code> as a unary expression with operator |
| <a href="/pkg/go/token#TILDE">token.TILDE</a>, |
| allowing better error recovery when a type constraint such as <code>~int</code> is used in an incorrect context. |
| </p> |
| </dd> |
| </dl><!-- go/parser --> |
| |
| <dl id="go/types"><dt><a href="/pkg/go/types/">go/types</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/51682 --><!-- CL 395535 --> |
| The new methods <a href="/pkg/go/types/#Func.Origin"><code>Func.Origin</code></a> |
| and <a href="/pkg/go/types/#Var.Origin"><code>Var.Origin</code></a> return the |
| corresponding <a href="/pkg/go/types/#Object"><code>Object</code></a> of the |
| generic type for synthetic <a href="/pkg/go/types/#Func"><code>Func</code></a> |
| and <a href="/pkg/go/types/#Var"><code>Var</code></a> objects created during type |
| instantiation. |
| </p> |
| <p><!-- https://go.dev/issue/52728 --><!-- CL 404885 --> |
| It is no longer possible to produce an infinite number of distinct-but-identical |
| <a href="/pkg/go/types/#Named"><code>Named</code></a> type instantiations via |
| recursive calls to |
| <a href="/pkg/go/types/#Named.Underlying"><code>Named.Underlying</code></a> or |
| <a href="/pkg/go/types/#Named.Method"><code>Named.Method</code></a>. |
| </p> |
| </dd> |
| </dl><!-- go/types --> |
| |
| |
| <dl id="hash/maphash"><dt><a href="/pkg/hash/maphash/">hash/maphash</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/42710 --><!-- CL 392494 --> |
| The new functions |
| <a href="/pkg/hash/maphash/#Bytes"><code>Bytes</code></a> |
| and |
| <a href="/pkg/hash/maphash/#String"><code>String</code></a> |
| provide an efficient way hash a single byte slice or string. |
| They are equivalent to using the more general |
| <a href="/pkg/hash/maphash/#Hash"><code>Hash</code></a> |
| with a single write, but they avoid setup overhead for small inputs. |
| </p> |
| </dd> |
| </dl><!-- hash/maphash --> |
| |
| <dl id="html/template"><dt><a href="/pkg/html/template/">html/template</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/46121 --><!-- CL 389156 --> |
| The type <a href="/pkg/html/template/#FuncMap"><code>FuncMap</code></a> |
| is now an alias for |
| <code>text/template</code>'s <a href="/pkg/text/template/#FuncMap"><code>FuncMap</code></a> |
| instead of its own named type. |
| This allows writing code that operates on a <code>FuncMap</code> from either setting. |
| </p> |
| </dd> |
| </dl><!-- html/template --> |
| |
| <dl id="image/draw"><dt><a href="/pkg/image/draw/">image/draw</a></dt> |
| <dd> |
| <p><!-- CL 396795 --> |
| <a href="/pkg/image/draw/#Draw"><code>Draw</code></a> with the |
| <a href="/pkg/image/draw/#Src"><code>Src</code></a> operator preserves |
| non-premultiplied-alpha colors when destination and source images are |
| both <a href="/pkg/image/#NRGBA"><code>image.NRGBA</code></a> |
| or both <a href="/pkg/image/#NRGBA64"><code>image.NRGBA64</code></a>. |
| This reverts a behavior change accidentally introduced by a Go 1.18 |
| library optimization; the code now matches the behavior in Go 1.17 and earlier. |
| </p> |
| </dd> |
| </dl><!-- image/draw --> |
| |
| <dl id="io"><dt><a href="/pkg/io/">io</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/51566 --><!-- CL 400236 --> |
| <a href="/pkg/io/#NopCloser"><code>NopCloser</code></a>'s result now implements |
| <a href="/pkg/io/#WriterTo"><code>WriterTo</code></a> |
| whenever its input does. |
| </p> |
| |
| <p><!-- https://go.dev/issue/50842 --> |
| <a href="/pkg/io/#MultiReader"><code>MultiReader</code></a>'s result now implements |
| <a href="/pkg/io/#WriterTo"><code>WriterTo</code></a> unconditionally. |
| If any underlying reader does not implement <code>WriterTo</code>, |
| it is simulated appropriately. |
| </p> |
| </dd> |
| </dl><!-- io --> |
| |
| <dl id="mime"><dt><a href="/pkg/mime/">mime</a></dt> |
| <dd> |
| <p><!-- CL 406894 --> |
| On Windows only, the mime package now ignores a registry entry |
| recording that the extension <code>.js</code> should have MIME |
| type <code>text/plain</code>. This is a common unintentional |
| misconfiguration on Windows systems. The effect is |
| that <code>.js</code> will have the default MIME |
| type <code>text/javascript; charset=utf-8</code>. |
| Applications that expect <code>text/plain</code> on Windows must |
| now explicitly call |
| <a href="/pkg/mime/#AddExtensionType"><code>AddExtensionType</code></a>. |
| </p> |
| </dd> |
| </dl> |
| |
| <dl id="net"><dt><a href="/pkg/net/">net</a></dt> |
| <dd> |
| <p><!-- CL 386016 --> |
| The pure Go resolver will now use EDNS(0) to include a suggested |
| maximum reply packet length, permitting reply packets to contain |
| up to 1232 bytes (the previous maximum was 512). |
| In the unlikely event that this causes problems with a local DNS |
| resolver, setting the environment variable |
| <code>GODEBUG=netdns=cgo</code> to use the cgo-based resolver |
| should work. |
| Please report any such problems on <a href="/issue/new">the |
| issue tracker</a>. |
| </p> |
| |
| <p><!-- https://go.dev/issue/51428 --><!-- CL 396877 --> |
| When a net package function or method returns an "I/O timeout" |
| error, the error will now satisfy <code>errors.Is(err, |
| context.DeadlineExceeded)</code>. When a net package function |
| returns an "operation was canceled" error, the error will now |
| satisfy <code>errors.Is(err, context.Canceled)</code>. |
| These changes are intended to make it easier for code to test |
| for cases in which a context cancellation or timeout causes a net |
| package function or method to return an error, while preserving |
| backward compatibility for error messages. |
| </p> |
| |
| <p><!-- https://go.dev/issue/33097 --><!-- CL 400654 --> |
| <a href="/pkg/net/#Resolver.PreferGo"><code>Resolver.PreferGo</code></a> |
| is now implemented on Windows and Plan 9. It previously only worked on Unix |
| platforms. Combined with |
| <a href="/pkg/net/#Dialer.Resolver"><code>Dialer.Resolver</code></a> and |
| <a href="/pkg/net/#Resolver.Dial"><code>Resolver.Dial</code></a>, it's now |
| possible to write portable programs and be in control of all DNS name lookups |
| when dialing. |
| </p> |
| |
| <p> |
| The <code>net</code> package now has initial support for the <code>netgo</code> |
| build tag on Windows. When used, the package uses the Go DNS client (as used |
| by <code>Resolver.PreferGo</code>) instead of asking Windows for |
| DNS results. The upstream DNS server it discovers from Windows |
| may not yet be correct with complex system network configurations, however. |
| </p> |
| </dd> |
| </dl><!-- net --> |
| |
| <dl id="net/http"><dt><a href="/pkg/net/http/">net/http</a></dt> |
| <dd> |
| <p><!-- CL 269997 --> |
| <a href="/pkg/net/http/#ResponseWriter"><code>ResponseWriter.WriteHeader</code></a> |
| now supports sending user-defined 1xx informational headers. |
| </p> |
| |
| <p><!-- CL 361397 --> |
| The <code>io.ReadCloser</code> returned by |
| <a href="/pkg/net/http/#MaxBytesReader"><code>MaxBytesReader</code></a> |
| will now return the defined error type |
| <a href="/pkg/net/http/#MaxBytesError"><code>MaxBytesError</code></a> |
| when its read limit is exceeded. |
| </p> |
| |
| <p><!-- CL 375354 --> |
| The HTTP client will handle a 3xx response without a |
| <code>Location</code> header by returning it to the caller, |
| rather than treating it as an error. |
| </p> |
| </dd> |
| </dl><!-- net/http --> |
| |
| <dl id="net/url"><dt><a href="/pkg/net/url/">net/url</a></dt> |
| <dd> |
| <p><!-- CL 374654 --> |
| The new |
| <a href="/pkg/net/url/#JoinPath"><code>JoinPath</code></a> |
| function and |
| <a href="/pkg/net/url/#URL.JoinPath"><code>URL.JoinPath</code></a> |
| method create a new <code>URL</code> by joining a list of path |
| elements. |
| </p> |
| <p><!-- https://go.dev/issue/46059 --> |
| The <code>URL</code> type now distinguishes between URLs with no |
| authority and URLs with an empty authority. For example, |
| <code>http:///path</code> has an empty authority (host), |
| while <code>http:/path</code> has none. |
| </p> |
| <p> |
| The new <a href="/pkg/net/url/#URL"><code>URL</code></a> field |
| <code>OmitHost</code> is set to <code>true</code> when a |
| <code>URL</code> has an empty authority. |
| </p> |
| |
| </dd> |
| </dl><!-- net/url --> |
| |
| <dl id="os/exec"><dt><a href="/pkg/os/exec/">os/exec</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/50599 --><!-- CL 401340 --> |
| A <a href="/pkg/os/exec/#Cmd"><code>Cmd</code></a> with a non-empty <code>Dir</code> field |
| and nil <code>Env</code> now implicitly sets the <code>PWD</code> environment |
| variable for the subprocess to match <code>Dir</code>. |
| </p> |
| <p> |
| The new method <a href="/pkg/os/exec/#Cmd.Environ"><code>Cmd.Environ</code></a> reports the |
| environment that would be used to run the command, including the |
| implicitly set <code>PWD</code> variable. |
| </p> |
| </dd> |
| </dl> <!-- os/exec --> |
| |
| <dl id="reflect"><dt><a href="/pkg/reflect/">reflect</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/47066 --><!-- CL 357331 --> |
| The method <a href="/pkg/reflect/#Value.Bytes"><code>Value.Bytes</code></a> |
| now accepts addressable arrays in addition to slices. |
| </p> |
| <p><!-- CL 400954 --> |
| The methods <a href="/pkg/reflect/#Value.Len"><code>Value.Len</code></a> |
| and <a href="/pkg/reflect/#Value.Cap"><code>Value.Cap</code></a> |
| now successfully operate on a pointer to an array and return the length of that array, |
| to match what the <a href="/ref/spec#Length_and_capacity">builtin |
| <code>len</code> and <code>cap</code> functions do</a>. |
| </p> |
| </dd> |
| </dl><!-- reflect --> |
| |
| <dl id="regexp/syntax"><dt><a href="/pkg/regexp/syntax/">regexp/syntax</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/51684 --><!-- CL 401076 --> |
| Go 1.18 release candidate 1, Go 1.17.8, and Go 1.16.15 included a security fix |
| to the regular expression parser, making it reject very deeply nested expressions. |
| 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 1.19 adds a more specific error, <a href="/pkg/regexp/syntax/#ErrNestingDepth"><code>syntax.ErrNestingDepth</code></a>, |
| which the parser now returns instead. |
| </p> |
| </dd> |
| </dl><!-- regexp --> |
| |
| <dl id="pkg-runtime"><dt><a href="/pkg/runtime/">runtime</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/51461 --> |
| The <a href="/pkg/runtime/#GOROOT"><code>GOROOT</code></a> function now returns the empty string |
| (instead of <code>"go"</code>) when the binary was built with |
| the <code>-trimpath</code> flag set and the <code>GOROOT</code> |
| variable is not set in the process environment. |
| </p> |
| </dd> |
| </dl><!-- runtime --> |
| |
| <dl id="runtime/metrics"><dt><a href="/pkg/runtime/metrics/">runtime/metrics</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/47216 --><!-- CL 404305 --> |
| The new <code>/sched/gomaxprocs:threads</code> |
| <a href="/pkg/runtime/metrics/#hdr-Supported_metrics">metric</a> reports |
| the current |
| <a href="/pkg/runtime/#GOMAXPROCS"><code>runtime.GOMAXPROCS</code></a> |
| value. |
| </p> |
| |
| <p><!-- https://go.dev/issue/47216 --><!-- CL 404306 --> |
| The new <code>/cgo/go-to-c-calls:calls</code> |
| <a href="/pkg/runtime/metrics/#hdr-Supported_metrics">metric</a> |
| reports the total number of calls made from Go to C. This metric is |
| identical to the |
| <a href="/pkg/runtime/#NumCgoCall"><code>runtime.NumCgoCall</code></a> |
| function. |
| </p> |
| |
| <p><!-- https://go.dev/issue/48409 --><!-- CL 403614 --> |
| The new <code>/gc/limiter/last-enabled:gc-cycle</code> |
| <a href="/pkg/runtime/metrics/#hdr-Supported_metrics">metric</a> |
| reports the last GC cycle when the GC CPU limiter was enabled. See the |
| <a href="#runtime">runtime notes</a> for details about the GC CPU limiter. |
| </p> |
| </dd> |
| </dl><!-- runtime/metrics --> |
| |
| <dl id="runtime/pprof"><dt><a href="/pkg/runtime/pprof/">runtime/pprof</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/33250 --><!-- CL 387415 --> |
| Stop-the-world pause times have been significantly reduced when |
| collecting goroutine profiles, reducing the overall latency impact to the |
| application. |
| </p> |
| |
| <p><!-- CL 391434 --> |
| <code>MaxRSS</code> is now reported in heap profiles for all Unix |
| operating systems (it was previously only reported for |
| <code>GOOS=android</code>, <code>darwin</code>, <code>ios</code>, and |
| <code>linux</code>). |
| </p> |
| </dd> |
| </dl><!-- runtime/pprof --> |
| |
| <dl id="runtime/race"><dt><a href="/pkg/runtime/race/">runtime/race</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/49761 --><!-- CL 333529 --> |
| The race detector has been upgraded to use thread sanitizer |
| version v3 on all supported platforms |
| except <code>windows/amd64</code> |
| and <code>openbsd/amd64</code>, which remain on v2. |
| Compared to v2, it is now typically 1.5x to 2x faster, uses half |
| as much memory, and it supports an unlimited number of |
| goroutines. |
| On Linux, the race detector now requires at least glibc version 2.17. |
| </p> |
| |
| <p><!-- CL 336549 --> |
| The race detector is now supported on <code>GOARCH=s390x</code>. |
| </p> |
| |
| <p><!-- https://go.dev/issue/52090 --> |
| Race detector support for <code>openbsd/amd64</code> has been |
| removed from thread sanitizer upstream, so it is unlikely to |
| ever be updated from v2. |
| </p> |
| </dd> |
| </dl><!-- runtime/race --> |
| |
| <dl id="runtime/trace"><dt><a href="/pkg/runtime/trace/">runtime/trace</a></dt> |
| <dd> |
| <p><!-- CL 400795 --> |
| When tracing and the |
| <a href="/pkg/runtime/pprof#StartCPUProfile">CPU profiler</a> are |
| enabled simultaneously, the execution trace includes CPU profile |
| samples as instantaneous events. |
| </p> |
| </dd> |
| </dl><!-- runtime/trace --> |
| |
| <dl id="sort"><dt><a href="/pkg/sort/">sort</a></dt> |
| <dd> |
| <p><!-- CL 371574 --> |
| The sorting algorithm has been rewritten to use |
| <a href="https://arxiv.org/pdf/2106.05123.pdf">pattern-defeating quicksort</a>, which |
| is faster for several common scenarios. |
| </p> |
| <p><!-- https://go.dev/issue/50340 --><!-- CL 396514 --> |
| The new function |
| <a href="/pkg/sort/#Find">Find</a> |
| is like |
| <a href="/pkg/sort/#Search">Search</a> |
| but often easier to use: it returns an additional boolean reporting whether an equal value was found. |
| </p> |
| </dd> |
| </dl><!-- sort --> |
| |
| <dl id="strconv"><dt><a href="/pkg/strconv/">strconv</a></dt> |
| <dd> |
| <p><!-- CL 397255 --> |
| <a href="/pkg/strconv/#Quote"><code>Quote</code></a> |
| and related functions now quote the rune U+007F as <code>\x7f</code>, |
| not <code>\u007f</code>, |
| for consistency with other ASCII values. |
| </p> |
| </dd> |
| </dl><!-- strconv --> |
| |
| <dl id="syscall"><dt><a href="/pkg/syscall/">syscall</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/51192 --><!-- CL 385796 --> |
| On PowerPC (<code>GOARCH=ppc64</code>, <code>ppc64le</code>), |
| <a href="/pkg/syscall/#Syscall"><code>Syscall</code></a>, |
| <a href="/pkg/syscall/#Syscall6"><code>Syscall6</code></a>, |
| <a href="/pkg/syscall/#RawSyscall"><code>RawSyscall</code></a>, and |
| <a href="/pkg/syscall/#RawSyscall6"><code>RawSyscall6</code></a> |
| now always return 0 for return value <code>r2</code> instead of an |
| undefined value. |
| </p> |
| |
| <p><!-- CL 391434 --> |
| On AIX and Solaris, <code>Getrusage</code> is now defined. |
| </p> |
| </dd> |
| </dl><!-- syscall --> |
| |
| <dl id="time"><dt><a href="/pkg/time/">time</a></dt> |
| <dd> |
| <p><!-- https://go.dev/issue/51414 --><!-- CL 393515 --> |
| The new method |
| <a href="/pkg/time/#Duration.Abs"><code>Duration.Abs</code></a> |
| provides a convenient and safe way to take the absolute value of a duration, |
| converting −2⁶³ to 2⁶³−1. |
| (This boundary case can happen as the result of subtracting a recent time from the zero time.) |
| </p> |
| <p><!-- https://go.dev/issue/50062 --><!-- CL 405374 --> |
| The new method |
| <a href="/pkg/time/#Time.ZoneBounds"><code>Time.ZoneBounds</code></a> |
| returns the start and end times of the time zone in effect at a given time. |
| It can be used in a loop to enumerate all the known time zone transitions at a given location. |
| </p> |
| </dd> |
| </dl><!-- time --> |
| |
| <!-- Silence these false positives from x/build/cmd/relnote: --> |
| <!-- CL 382460 --> |
| <!-- CL 384154 --> |
| <!-- CL 384554 --> |
| <!-- CL 392134 --> |
| <!-- CL 392414 --> |
| <!-- CL 396215 --> |
| <!-- CL 403058 --> |
| <!-- CL 410133 --> |
| <!-- https://go.dev/issue/27837 --> |
| <!-- https://go.dev/issue/38340 --> |
| <!-- https://go.dev/issue/42516 --> |
| <!-- https://go.dev/issue/45713 --> |
| <!-- https://go.dev/issue/46654 --> |
| <!-- https://go.dev/issue/48257 --> |
| <!-- https://go.dev/issue/50447 --> |
| <!-- https://go.dev/issue/50720 --> |
| <!-- https://go.dev/issue/50792 --> |
| <!-- https://go.dev/issue/51115 --> |
| <!-- https://go.dev/issue/51447 --> |