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.
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The -trimpath flag, if set, is now included in the build settings
stamped into Go binaries by go build, and can be
examined using
go version -m
or debug.ReadBuildInfo.
go generate now sets the GOROOT
environment variable explicitly in the generator's environment, so that
generators can locate the correct GOROOT even if built
with -trimpath.
go test and go generate now place
GOROOT/bin at the beginning of the PATH used for the
subprocess, so tests and generators that execute the go command
will resolve it to same GOROOT.
go env now quotes entries that contain spaces in
the CGO_CFLAGS, CGO_CPPFLAGS, CGO_CXXFLAGS, CGO_FFLAGS, CGO_LDFLAGS,
and GOGCCFLAGS variables it reports.
unix build constraint
The build constraint unix is now recognized
in //go:build lines. The constraint is satisfied
if the target operating system, also known as GOOS, is
a Unix or Unix-like system. For the 1.19 release it is satisfied
if GOOS is one of
aix, android, darwin,
dragonfly, freebsd, hurd,
illumos, ios, linux,
netbsd, openbsd, or solaris.
In future releases the unix constraint may match
additional newly supported operating systems.
TODO: soft memory limit
TODO: idle mark workers
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.
On Unix operating systems, Go programs that import package
os now automatically increase the open file limit
(RLIMIT_NOFILE) to the maximum allowed value. Programs that need
a lower limit (for compatibility with select, for example) can
set the limit back as needed, or lower the hard limit prior to starting the
Go program.
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 GOTRACEBACK=system or
crash. Runtime-internal fatal error tracebacks always include
full metadata regardless of the value of GOTRACEBACK
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.
The compiler now uses
a jump
table to implement large integer and string switch statements.
Performance improvements for the switch statement vary but can be
on the order of 20% faster.
(GOARCH=amd64 and GOARCH=arm64 only)
TODO: https://go.dev/cl/402374: enable regabi on riscv64 by default
TODO: https://go.dev/cl/391014: The Go compiler now requires the -p=importpath flag, which is already supplied by the go 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 in order to use Go 1.19.: cmd/compile: require -p flag
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The sync/atomic package defines new atomic types
Bool,
Int32,
Int64,
Uint32,
Uint64,
Uintptr, and
Pointer.
These types hide the underlying values so that all accesses are forced to use
the atomic APIs.
Pointer also avoids
the need to convert to
unsafe.Pointer at call sites.
Int64 and
Uint64 automatically
receive 64-bit alignment on ARM, 386, and 32-bit MIPS required for 64-bit
atomics on these systems.
TODO: https://go.dev/issue/51940: all: move dev.boringcrypto into main branch behind GOEXPERIMENT
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As always, there are various minor changes and updates to the library, made with the Go 1 promise of compatibility in mind.
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TODO: https://go.dev/cl/387976: permit zip files to have prefixes
TODO: https://go.dev/cl/370894: batch and buffer calls to getrandom/getentropy
TODO: https://go.dev/cl/375215: use fast key erasure RNG on plan9 instead of ANSI X9.31
TODO: https://go.dev/cl/390038: remove all buffering
The tls10default GODEBUG option has been
removed. It is still possible to enable TLS 1.0 client-side by setting
Config.MinVersion.
TODO: https://go.dev/cl/285872: disable signing with MD5WithRSA
TODO: https://go.dev/cl/386017: add AppendByteOrder
TODO: https://go.dev/cl/405675: add Reader.InputOffset method
TODO: https://go.dev/cl/313329: add TextVar function
TODO: https://go.dev/cl/406177: add Append, Appendln, Appendf
TODO: https://go.dev/cl/403696: parser to accept ~x as unary expression
Draw with the Src operator preserves
non-premultiplied-alpha colors when destination and source images are
both *image.NRGBA (or both *image.NRGBA64).
This reverts a behavior change accidentally introduced by a Go 1.18
library optimization, to match the behavior in Go 1.17 and earlier.
TODO: https://go.dev/cl/400236: NopCloser forward WriterTo implementations if the reader supports it
On Windows only, the mime package now ignores a registry entry
recording that the extension .js should have MIME
type text/plain. This is a common unintentional
misconfiguration on Windows systems. The effect is
that .js will have the default MIME
type text/javascript; charset=utf-8.
Applications that expect text/plain on Windows must
now explicitly call
AddExtensionType.
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
GODEBUG=netdns=cgo to use the cgo-based resolver
should work.
Please report any such problems on the
issue tracker.
When a net package function or method returns an "I/O timeout"
error, the error will now satisfy errors.Is(err,
context.DeadlineExceeded). When a net package function
returns an "operation was canceled" error, the error will now
satisfy errors.Is(err, context.Canceled).
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.
TODO: https://go.dev/cl/400654: permit use of Resolver.PreferGo, netgo on Windows and Plan 9
TODO: https://go.dev/cl/269997: allow sending 1xx responses
TODO: https://go.dev/cl/374654: add JoinPath, URL.JoinPath
TODO: https://go.dev/cl/392415: raise open file rlimit at startup
An exec.Cmd with a non-empty Dir and a
nil Env now implicitly sets the PWD environment
variable for the subprocess to match Dir.
The new method (*exec.Cmd).Environ reports the
environment that would be used to run the command, including the
aforementioned PWD variable.
The method Value.Bytes now accepts addressable arrays in addition to slices.
The methods Value.Len and Value.Cap now successfully operate on a pointer to an array and return the length of that array, to match what the builtin len and cap functions do.
The GOROOT function now returns the empty string
(instead of "go") when the binary was built with
the -trimpath flag set and the GOROOT
variable is not set in the process environment.
The new /sched/gomaxprocs:threads metric reports the current
runtime.GOMAXPROCS value.
The new /cgo/go-to-c-calls:calls metric reports the total
number of calls made from Go to C. This metric is identical to the runtime.NumCgoCall
function.
The new /gc/limiter/last-enabled:gc-cycle metric reports the
last GC cycle when the GC CPU limiter was enabled.
Stop-the-world pause times have been significantly reduced when collecting goroutine profiles, reducing the overall latency impact to the application.
MaxRSS is now reported in heap profiles for all Unix
operating systems (it was previously only reported for
GOOS=android, darwin, ios, and
linux).
The race detector has been upgraded to use thread sanitizer version v3.
The race detector is now supported on S390.
When used together with the CPU profiler, the execution trace includes CPU profile samples.
The sorting algorithm has been rewritten to use pattern-defeating quicksort, which is faster for several common scenarios.
Quote
and related functions now quote the rune 007F as \x7f,
not \u007f.
On PowerPC (GOARCH=ppc64, ppc64le),
Syscall,
Syscall6,
RawSyscall, and
RawSyscall6
now always return 0 for return value r2 instead of an
undefined value.
On AIX and Solaris, Getrusage is now defined.
TODO: https://go.dev/cl/393515: add Duration.Abs