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>

	{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"}},

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.

		return errors.New("archive/zip: invalid duplicate FileHeader")
	}
	return nil
}

// CreateHeader adds a file to the zip archive using the provided [FileHeader]
// for the file metadata. [Writer] takes ownership of fh and may mutate
// its fields. The caller must not modify fh after calling [Writer.CreateHeader].
//
// This returns a [Writer] to which the file contents should be written.

		default:
			take(&required)
			take(&features)
		}
	}

	return ok
}

// aliasReplacer applies type aliases to earlier API files,
// to avoid misleading negative results.
// This makes all the references to os.FileInfo in go1.txt
// be read as if they said fs.FileInfo, since os.FileInfo is now an alias.
// If there are many of these, we could do a more general solution,
// but for now the replacer is fine.

	var paxHdrs map[string]string
	var gnuLongName, gnuLongLink string

	// Externally, Next iterates through the tar archive as if it is a series of
	// files. Internally, the tar format often uses fake "files" to add meta
	// data that describes the next file. These meta data "files" should not
	// normally be visible to the outside. As such, this loop iterates through
	// one or more "header files" until it finds a "normal file".

<a href="/pkg/sync/#Map">lock-free maps</a>,
<a href="/pkg/sync/#Pool">allocation pools</a>,
and
<a href="/pkg/sync/#WaitGroup">wait groups</a>.
The documentation for each of these specifies the guarantees it
makes concerning synchronization.
</p>

<p>
Other packages that provide synchronization abstractions
should document the guarantees they make too.
</p>


<h2 id="badsync">Incorrect synchronization</h2>

	"sync"
	"syscall"
)

func init() {
	sysStat = statUnix
}

// userMap and groupMap caches UID and GID lookups for performance reasons.
// The downside is that renaming uname or gname by the OS never takes effect.
var userMap, groupMap sync.Map // map[int]string

func statUnix(fi fs.FileInfo, h *Header, doNameLookups bool) error {
	sys, ok := fi.Sys().(*syscall.Stat_t)
	if !ok {
		return nil
	}
	h.Uid = int(sys.Uid)