</p>

<h2 id="badcompiler">Incorrect compilation</h2>

<p>
The Go memory model restricts compiler optimizations as much as it does Go programs.
Some compiler optimizations that would be valid in single-threaded programs are not valid in all Go programs.
In particular, a compiler must not introduce writes that do not exist in the original program,
it must not allow a single read to observe multiple values,

</p>

<h3 id="arm">Arm</h3>
<p><!-- CL 514907 -->
  The <code>GOARM</code> environment variable now allows you to select whether to use software or hardware floating point.
  Previously, valid <code>GOARM</code> values were <code>5</code>, <code>6</code>, or <code>7</code>. Now those same values can
  be optionally followed by <code>,softfloat</code> or <code>,hardfloat</code> to select the floating-point implementation.
</p>

\n   U+000A line feed or newline
\r   U+000D carriage return
\t   U+0009 horizontal tab
\v   U+000B vertical tab
\\   U+005C backslash
\'   U+0027 single quote  (valid escape only within rune literals)
\"   U+0022 double quote  (valid escape only within string literals)
</pre>

<p>
All other sequences starting with a backslash are illegal inside rune literals.
</p>
<pre class="ebnf">

\n   U+000A line feed or newline
\r   U+000D carriage return
\t   U+0009 horizontal tab
\v   U+000B vertical tab
\\   U+005C backslash
\'   U+0027 single quote  (valid escape only within rune literals)
\"   U+0022 double quote  (valid escape only within string literals)
</pre>

<p>
An unrecognized character following a backslash in a rune literal is illegal.
</p>

<pre class="ebnf">

</li>
<li>
<code>NOFRAME</code> = 512
<br>
(For <code>TEXT</code> items.)
Do not insert instructions to allocate a stack frame and save/restore the return
address, even if this is not a leaf function.
Only valid on functions that declare a frame size of 0.
</li>
<li>
<code>TOPFRAME</code> = 2048
<br>
(For <code>TEXT</code> items.)
Function is the outermost frame of the call stack. Traceback should stop at this function.