</p>

<p>
Global data symbols are defined by a sequence of initializing
<code>DATA</code> directives followed by a <code>GLOBL</code> directive.
Each <code>DATA</code> directive initializes a section of the
corresponding memory.
The memory not explicitly initialized is zeroed.
The general form of the <code>DATA</code> directive is

<pre>
DATA	symbol+offset(SB)/width, value
</pre>

<p>

to be made when linking the final binary.

Linking Directives

In either linking mode, package-specific directives must be passed
through to cmd/link. These are communicated by writing //go: directives in a
Go source file compiled by gc. The directives are copied into the .o
object file and then processed by the linker.

The directives are:

//go:cgo_import_dynamic <local> [<remote> ["<library>"]]

func (in *Input) enabled() bool {
	return len(in.ifdefStack) == 0 || in.ifdefStack[len(in.ifdefStack)-1]
}

func (in *Input) expectNewline(directive string) {
	tok := in.Stack.Next()
	if tok != '\n' {
		in.expectText("expected newline after", directive)
	}
}

func (in *Input) Next() ScanToken {
	if in.peek {
		in.peek = false
		tok := in.peekToken
		in.text = in.peekText
		return tok
	}

can include one or more `//go:debug` directives at the top of the file
(preceding the `package` statement).
Continuing the `panicnil` example, if the module or workspace is updated
to say `go` `1.21`, the program can opt back into the old `panic(nil)`
behavior by including this directive:

	//go:debug panicnil=1

Starting in Go 1.21, the Go toolchain treats a `//go:debug` directive

pkg go/build, type Directive struct #56986
pkg go/build, type Directive struct, Pos token.Position #56986
pkg go/build, type Directive struct, Text string #56986
pkg go/build, type Package struct, Directives []Directive #56986
pkg go/build, type Package struct, TestDirectives []Directive #56986
pkg go/build, type Package struct, XTestDirectives []Directive #56986
pkg go/token, method (*File) Lines() []int #57708