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doc: document more cgo, go command changes
Also document new cgo changes and reorder go command section to put most important notes first. Change-Id: I45b0c785bd8bc82c3b174800fc995312ea057f14 Reviewed-on: https://go-review.googlesource.com/c/go/+/452557 Reviewed-by: Bryan Mills <bcmills@google.com> Run-TryBot: Russ Cox <rsc@golang.org> TryBot-Result: Gopher Robot <gobot@golang.org> Auto-Submit: Russ Cox <rsc@golang.org>
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Russ Cox
Gopher Robot
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doc/go1.20.html
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doc/go1.20.html
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@ -51,28 +51,66 @@ Do not send CLs removing the interior tags from such phrases.
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<h3 id="go-command">Go command</h3>
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<p><!-- https://go.dev/issue/38687, CL 421440 -->
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TODO: <a href="https://go.dev/cl/421440">https://go.dev/cl/421440</a>: cmd/go: add go generate -skip flag
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<p><!-- CL 432535: cmd/go: don't install most GOROOT .a files in pkg -->
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The directory <code>$GOROOT/pkg</code> no longer stores
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pre-compiled package archives for the standard library:
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<code>go</code> <code>install</code> no longer writes them,
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the <code>go</code> build no longer checks for them,
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and the Go distribution no longer ships them.
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Instead, packages in the standard library are built as needed
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and cached in the build cache, just like packages outside <code>GOROOT</code>.
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This change reduces the size of the Go distribution and also
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avoids C toolchain skew for packages that use cgo.
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</p>
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<p><!-- CL 448357: cmd/go: print test2json start events -->
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The implementation of <code>go</code> <code>test</code> <code>-json</code>
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has been improved to make it more robust.
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Programs that run <code>go</code> <code>test</code> <code>-json</code>
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do not need any updates.
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Programs that invoke <code>go</code> <code>tool</code> <code>test2json</code>
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directly should now run the test binary with <code>-v=json</code>
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(for example, <code>go</code> <code>test</code> <code>-v=json</code>
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or <code>./pkg.test</code> <code>-test.v=json</code>)
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instead of plain <code>-v</code>.
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</p>
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<p><!-- CL 448357: cmd/go: print test2json start events -->
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A related change to <code>go</code> <code>test</code> <code>-json</code>
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is the addition of an event with <code>Action</code> set to <code>start</code>
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at the beginning of each test program's execution.
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When running multiple tests using the <code>go</code> command,
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these start events are guaranteed to be emitted in the same order as
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the packages named on the command line.
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</p>
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<p><!-- https://go.dev/issue/45454 -->
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TODO: <a href="https://go.dev/issue/45454">https://go.dev/issue/45454</a>: provide build tags for architecture environment variables
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</p>
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<p><!-- CL 448357: cmd/go: print test2json start events -->
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TODO: CL 448357: cmd/go: print test2json start events
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<p><!-- https://go.dev/issue/50332 -->
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The <code>go</code> subcommands now accept
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<code>-C</code> <code><dir></code> to change directory to <dir>
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before performing the command, which may be useful for scripts that need to
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execute commands in multiple different modules.
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</p>
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<p><!-- CL 432535: cmd/go: don't install most GOROOT .a files in pkg -->
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The Go distribution no longer ships with pre-compiled <code>.a</code>
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files for most of the packages in <code>GOROOT</code>, now only including
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.a files for the five packages in <code>GOROOT</code> that use <code>cgo</code>.
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Instead, those packages will be built as needed and cached in the build
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cache, as is already done for non-<code>main</code> packages outside
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<code>GOROOT</code>. Further, <code>go</code> <code>install</code> will
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also not install <code>.a</code> files for <code>GOROOT</code> packages
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except for those that use <code>cgo</code>. These changes are intended to
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reduce the size of the Go distribution, in some cases by up to two-thirds.
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<p><!-- https://go.dev/issue/41696, CL 416094 -->
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The <code>go</code> <code>build</code> and <code>go</code> <code>test</code>
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commands no longer accept the <code>-i</code> flag,
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which has been <a href="https://go.dev/issue/41696">deprecated since Go 1.16</a>.
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</p>
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<p><!-- https://go.dev/issue/38687, CL 421440 -->
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The <code>go</code> <code>generate</code> command now accepts
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<code>-skip</code> <code><pattern></code> to skip <code>//go:generate</code> directives
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matching <code><pattern></code>.
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</p>
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<p><!-- https://go.dev/issue/41583 -->
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The <code>go</code> <code>test</code> command now accepts
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<code>-skip</code> <code><pattern></code> to skip tests, subtests, or examples
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matching <code><pattern></code>.
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</p>
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<p><!-- https://go.dev/issue/37015 -->
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@ -86,25 +124,6 @@ Do not send CLs removing the interior tags from such phrases.
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the <code>GOPATH</code> install targets to unexpectedly remain in effect.)
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</p>
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<p><!-- https://go.dev/issue/41696, CL 416094 -->
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The <code>-i</code> flag is no longer accepted by
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<code>go</code> <code>build</code> and <code>go</code> <code>test</code>.
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The flag has been <a href="https://go.dev/issue/41696">deprecated since Go 1.16</a>.
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</p>
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<p><!-- https://go.dev/issue/50332 -->
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The <code>go</code> subcommands now accept
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<code>-C</code> <code><dir></code> to change directory to <dir>
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before performing the command, which may be useful for scripts that need to
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execute commands in multiple different modules.
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</p>
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<p><!-- https://go.dev/issue/41583 -->
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The <code>go</code> <code>test</code> command now accepts
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<code>-skip</code> <code><pattern></code> to skip tests or subtests
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matching <code><pattern></code>.
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</p>
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<h4 id="go-version"><code>go</code> <code>version</code></h4>
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<p><!-- https://go.dev/issue/48187 -->
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@ -114,6 +133,47 @@ Do not send CLs removing the interior tags from such phrases.
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and Linux binaries without execute permission.
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</p>
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<h3 id="cgo">Cgo</h3>
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<p>
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The <code>go</code> command now disables <code>cgo</code> by default
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on systems without a C toolchain.
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More specifically, when the <code>CGO_ENABLED</code> environment variable is unset,
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the <code>CC</code> environment variable is unset,
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and the default C compiler (typically <code>clang</code> or <code>gcc</code>)
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is not found in the path,
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<code>CGO_ENABLED</code> defaults to <code>0</code>.
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As always, you can override the default by setting <code>CGO_ENABLED</code> explicitly.
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</p>
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<p>
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The most important effect of the default change is that when Go is installed
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on a system without a C compiler, it will now use pure Go builds for packages
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in the standard library that use cgo, instead of using pre-distributed package archives
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(which have been removed, as <a href="#go-command">noted above</a>)
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or attempting to use cgo and failing.
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This makes Go work better in some minimal container environments
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as well as on macOS, where pre-distributed package archives have
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not been used for cgo-based packages since Go 1.16.
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</p>
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<p>
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The packages in the standard library that use cgo are <a href="/pkg/net/">net</a>,
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<a href="/pkg/os/user/">os/user</a>, and
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<a href="/pkg/plugin/">plugin</a>.
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On macOS, the net and os/user packages have been rewritten not to use cgo:
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the same code is now used for cgo and non-cgo builds as well as cross-compiled builds.
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On Windows, the net and os/user packages have never used cgo.
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On other systems, builds with cgo disabled will use a pure Go version of these packages.
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</p>
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<p>
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On macOS, the race detector has been rewritten not to use cgo:
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race-detector-enabled programs can be built and run without Xcode.
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On Linux and other Unix systems, and on Windows, a host C toolchain
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is required to use the race detector.
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</p>
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<h3 id="cover">Cover</h3>
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<p><!-- CL 436236, CL 401236, CL 438503 -->
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@ -630,7 +690,7 @@ proxyHandler := &httputil.ReverseProxy{
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</p>
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<p><!-- https://go.dev/issue/53896 -->
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HTTP/2 stream errors returned by <code>net/http</code> functions may be converted
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HTTP/2 stream errors returned by <code>net/http</code> functions may be converted
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to a <code>"golang.org/x/net/http2".StreamError</code> using <code>errors.As</code>.
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</p>
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