<p>
Constants are of the form <code>const_<i>name</i></code>.
For example, given the Go declaration <code>const bufSize =
1024</code>, assembly code can refer to the value of this constant
as <code>const_bufSize</code>.
</p>

<p>
Field offsets are of the form <code><i>type</i>_<i>field</i></code>.
Struct sizes are of the form <code><i>type</i>__size</code>.
For example, consider the following Go definition:
</p>

<pre>

	var files = []struct {
		Name, Body string
	}{
		{"readme.txt", "This archive contains some text files."},
		{"gopher.txt", "Gopher names:\nGeorge\nGeoffrey\nGonzo"},
		{"todo.txt", "Get animal handling licence.\nWrite more examples."},
	}
	for _, file := range files {
		f, err := w.Create(file.Name)
		if err != nil {
			log.Fatal(err)
		}
		_, err = f.Write([]byte(file.Body))
		if err != nil {
			log.Fatal(err)
		}
	}

	Note that the arguments are for "gcc", not "ld".

	Example:
	//go:cgo_ldflag "-lpthread"
	//go:cgo_ldflag "-L/usr/local/sqlite3/lib"

A package compiled with cgo will include directives for both
internal and external linking; the linker will select the appropriate
subset for the chosen linking mode.

Example

As a simple example, consider a package that uses cgo to call C.sin.

For instance, this example:
</p>

<pre>
	goto L  // BAD
	v := 3
L:
</pre>

<p>
is erroneous because the jump to label <code>L</code> skips
the creation of <code>v</code>.
</p>

<p>
A "goto" statement outside a <a href="#Blocks">block</a> cannot jump to a label inside that block.
For instance, this example:
</p>

<pre>
if n%2 == 1 {

cui fliter <******@****.***> 1709194171 +0800

favonia <******@****.***> 1684978995 -0400

				}
			}
		})
	}
}

type operandTest struct {
	input, output string
}

type badOperandTest struct {
	input, error string
}

// Examples collected by scanning all the assembly in the standard repo.

var amd64OperandTests = []operandTest{
	{"$(-1.0)", "$(-1.0)"},
	{"$(0.0)", "$(0.0)"},
	{"$(0x2000000+116)", "$33554548"},
	{"$(0x3F<<7)", "$8064"},

slices, and strings in most Go implementations,
such races can in turn lead to arbitrary memory corruption.
</p>

<p>
Examples of incorrect synchronization are given in the
“Incorrect synchronization” section below.
</p>

<p>
Examples of the limitations on implementations are given in the
“Incorrect compilation” section below.
</p>

<h2 id="synchronization">Synchronization</h2>

A GODEBUG setting is a `key=value` pair
that controls the execution of certain parts of a Go program.
The environment variable `GODEBUG`
can hold a comma-separated list of these settings.
For example, if a Go program is running in an environment that contains

	GODEBUG=http2client=0,http2server=0

then that Go program will disable the use of HTTP/2 by default in both
the HTTP client and the HTTP server.

The [DNSError] type now wraps errors caused by timeouts or cancellation.
For example, `errors.Is(someDNSErr, context.DeadlineExceedeed)`