well as the system-specific header locations and system-specific
pre-#defined macros. This is certainly possible to do, but it is an
enormous amount of work.

Cgo takes a different approach. It determines the meaning of C
identifiers not by parsing C code but by feeding carefully constructed
programs into the system C compiler and interpreting the generated

</p>

<p>
A new, initialized slice value for a given element type <code>T</code> is
made using the built-in function
<a href="#Making_slices_maps_and_channels"><code>make</code></a>,
which takes a slice type
and parameters specifying the length and optionally the capacity.
A slice created with <code>make</code> always allocates a new, hidden array
to which the returned slice value refers. That is, executing
</p>

// using octal encoding with the appropriate NUL terminator.
func fitsInOctal(n int, x int64) bool {
	octBits := uint(n-1) * 3
	return x >= 0 && (n >= 22 || x < 1<<octBits)
}

// parsePAXTime takes a string of the form %d.%d as described in the PAX
// specification. Note that this implementation allows for negative timestamps,
// which is allowed for by the PAX specification, but not always portable.

	slice, err := b.readSlice(delim)
	return string(slice), err
}

// NewBuffer creates and initializes a new [Buffer] using buf as its
// initial contents. The new [Buffer] takes ownership of buf, and the
// caller should not use buf after this call. NewBuffer is intended to
// prepare a [Buffer] to read existing data. It can also be used to set

  x.go:3		0x1050203		e83882ffff		CALL runtime.morestack_noctxt(SB)
  x.go:3		0x1050208		ebb6			JMP main.main(SB)
</pre>

<h3 id="constants">Constants</h3>

<p>
Although the assembler takes its guidance from the Plan 9 assemblers,
it is a distinct program, so there are some differences.
One is in constant evaluation.
Constant expressions in the assembler are parsed using Go's operator

	{abcd, "", -1, []string{"a", "b", "c", "d"}},
	{commas, ",", -1, []string{"1", "2", "3", "4"}},
	{dots, "...", -1, []string{"1", ".2", ".3", ".4"}},
	{faces, "☹", -1, []string{"☺☻", ""}},
	{faces, "~", -1, []string{faces}},
	{faces, "", -1, []string{"☺", "☻", "☹"}},
	{"1 2 3 4", " ", 3, []string{"1", "2", "3 4"}},
	{"1 2", " ", 3, []string{"1", "2"}},
	{"123", "", 2, []string{"1", "23"}},

			// Drop misaligned fields, the same way we drop integer bit fields.
			// The goal is to make available what can be made available.
			// Otherwise one bad and unneeded field in an otherwise okay struct
			// makes the whole program not compile. Much of the time these
			// structs are in system headers that cannot be corrected.
			continue
		}

		// Round off up to talign, assumed to be a power of 2.

	// Since ZIP lacked high precision timestamps (nor an official specification
	// of the timezone used for the date fields), many competing extra fields
	// have been invented. Pervasive use effectively makes them "official".
	//
	// See http://mdfs.net/Docs/Comp/Archiving/Zip/ExtraField
	zip64ExtraID       = 0x0001 // Zip64 extended information
	ntfsExtraID        = 0x000a // NTFS
	unixExtraID        = 0x000d // UNIX

and the [go command documentation](/cmd/go#hdr-Build_and_test_caching).

### Go 1.23

Go 1.23 changed the channels created by package time to be unbuffered
(synchronous), which makes correct use of the [`Timer.Stop`](/pkg/time/#Timer.Stop)
and [`Timer.Reset`](/pkg/time/#Timer.Reset) method results much easier.
The [`asynctimerchan` setting](/pkg/time/#NewTimer) disables this change.

// equivalent to that from a range loop over the input as a string, which
// means that erroneous UTF-8 encodings translate to U+FFFD = "\xef\xbf\xbd".
// Because of the Scan interface, this makes it impossible for the client to
// distinguish correctly encoded replacement runes from encoding errors.
func ScanRunes(data []byte, atEOF bool) (advance int, token []byte, err error) {
	if atEOF && len(data) == 0 {