ExpressionStmt = Expression .
</pre>

<p>
The following built-in functions are not permitted in statement context:
</p>

<pre>
append cap complex imag len make new real
unsafe.Add unsafe.Alignof unsafe.Offsetof unsafe.Sizeof unsafe.Slice
</pre>

<pre>
h(x+y)
f.Close()
&lt;-ch
(&lt;-ch)
len("foo")  // illegal if len is the built-in function
</pre>

<code>l.TryLock</code> (or <code>l.TryRLock</code>)
may be considered to be able to return false
even when the mutex <i>l</i> is unlocked.
</p>

<h3 id="once">Once</h3>

<p>
The <code>sync</code> package provides a safe mechanism for
initialization in the presence of multiple goroutines
through the use of the <code>Once</code> type.
Multiple threads can execute <code>once.Do(f)</code> for a particular <code>f</code>,

When using the compiler and assembler's
<code>-dynlink</code> or <code>-shared</code> modes,
any load or store of a fixed memory location such as a global variable
must be assumed to overwrite <code>CX</code>.
Therefore, to be safe for use with these modes,
assembly sources should typically avoid CX except between memory references.
</p>

<h3 id="amd64">64-bit Intel 386 (a.k.a. amd64)</h3>

<p>

</pre>

<p>
The following built-in functions are not permitted in statement context:
</p>

<pre>
append cap complex imag len make new real
unsafe.Add unsafe.Alignof unsafe.Offsetof unsafe.Sizeof unsafe.Slice unsafe.SliceData unsafe.String unsafe.StringData
</pre>

<pre>
h(x+y)
f.Close()
&lt;-ch
(&lt;-ch)
len("foo")  // illegal if len is the built-in function
</pre>