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<div class="section" id="snc-stack-no-checking">
<span id="pool-snc"></span><span id="index-0"></span><h1>13. SNC (Stack No Checking)<a class="headerlink" href="#snc-stack-no-checking" title="Permalink to this headline"></a></h1>
<div class="admonition-deprecated admonition">
<p class="first admonition-title">Deprecated</p>
<p>starting with version 1.111.</p>
<p class="last">If you need special handling of stack-like allocation,
<a class="reference internal" href="../contact.html#contact"><em>contact us</em></a>.</p>
</div>
<p><strong>SNC</strong> is a <a class="reference internal" href="../glossary/m.html#term-manual-memory-management"><em class="xref std std-term">manually managed</em></a>
<a class="reference internal" href="../glossary/p.html#term-pool-class"><em class="xref std std-term">pool class</em></a> that supports a stack-like protocol for allocation
and deallocation using <a class="reference internal" href="../glossary/a.html#term-allocation-frame"><em class="xref std std-term">allocation frames</em></a> on <a class="reference internal" href="../glossary/a.html#term-allocation-point"><em class="xref std std-term">allocation
points</em></a>. See <a class="reference internal" href="../topic/frame.html#topic-frame"><em>Allocation frames</em></a>.</p>
<p>If <a class="reference internal" href="../topic/frame.html#mps_ap_frame_pop" title="mps_ap_frame_pop"><tt class="xref c c-func docutils literal"><span class="pre">mps_ap_frame_pop()</span></tt></a> is used on an allocation point in an SNC
pool (after a corresponding call to <a class="reference internal" href="../topic/frame.html#mps_ap_frame_push" title="mps_ap_frame_push"><tt class="xref c c-func docutils literal"><span class="pre">mps_ap_frame_push()</span></tt></a>), then
the objects affected by the pop are effectively declared dead, and may
be reclaimed by the collector. Extant references to such objects from
reachable or <em>de facto</em> alive objects are safe, but such other objects
should be dead; that is, such references must never be used.</p>
<div class="section" id="snc-properties">
<span id="index-1"></span><h2>13.1. SNC properties<a class="headerlink" href="#snc-properties" title="Permalink to this headline"></a></h2>
<ul class="simple">
<li>Does not support allocation via <a class="reference internal" href="../topic/allocation.html#mps_alloc" title="mps_alloc"><tt class="xref c c-func docutils literal"><span class="pre">mps_alloc()</span></tt></a>.</li>
<li>Supports allocation via <a class="reference internal" href="../glossary/a.html#term-allocation-point"><em class="xref std std-term">allocation points</em></a> only. If an
allocation point is created in an SNC pool, the call to
<a class="reference internal" href="../topic/allocation.html#mps_ap_create" title="mps_ap_create"><tt class="xref c c-func docutils literal"><span class="pre">mps_ap_create()</span></tt></a> takes no additional parameters.</li>
<li>Does not support deallocation via <a class="reference internal" href="../topic/allocation.html#mps_free" title="mps_free"><tt class="xref c c-func docutils literal"><span class="pre">mps_free()</span></tt></a>.</li>
<li>Supports <a class="reference internal" href="../glossary/a.html#term-allocation-frame"><em class="xref std std-term">allocation frames</em></a>.</li>
<li>Does not support <a class="reference internal" href="../glossary/s.html#term-segregated-allocation-cache"><em class="xref std std-term">segregated allocation caches</em></a>.</li>
<li>Blocks may contain <a class="reference internal" href="../glossary/e.html#term-exact-reference"><em class="xref std std-term">exact references</em></a> to blocks in the same or
other pools (but may not contain <a class="reference internal" href="../glossary/a.html#term-ambiguous-reference"><em class="xref std std-term">ambiguous references</em></a> or
<a class="reference internal" href="../glossary/w.html#term-weak-reference-1"><em class="xref std std-term">weak references<sup>(1)</sup></em></a>, and may not use <a class="reference internal" href="../glossary/r.html#term-remote-reference"><em class="xref std std-term">remote
references</em></a>).</li>
<li>There are no garbage collections in this pool.</li>
<li>Allocations may be variable in size.</li>
<li>The <a class="reference internal" href="../glossary/a.html#term-alignment"><em class="xref std std-term">alignment</em></a> of blocks is configurable.</li>
<li>Blocks do not have <a class="reference internal" href="../glossary/d.html#term-dependent-object"><em class="xref std std-term">dependent objects</em></a>.</li>
<li>Blocks are not automatically <a class="reference internal" href="../glossary/r.html#term-reclaim"><em class="xref std std-term">reclaimed</em></a>.</li>
<li>Blocks are <a class="reference internal" href="../glossary/s.html#term-scan"><em class="xref std std-term">scanned</em></a>.</li>
<li>Blocks may only be referenced by <a class="reference internal" href="../glossary/b.html#term-base-pointer"><em class="xref std std-term">base pointers</em></a>.</li>
<li>Blocks are not protected by <a class="reference internal" href="../glossary/b.html#term-barrier-1"><em class="xref std std-term">barriers<sup>(1)</sup></em></a>.</li>
<li>Blocks do not <a class="reference internal" href="../glossary/m.html#term-moving-garbage-collector"><em class="xref std std-term">move</em></a>.</li>
<li>Blocks may not be registered for <a class="reference internal" href="../glossary/f.html#term-finalization"><em class="xref std std-term">finalization</em></a>. A consequence
of this is that the pool&#8217;s <a class="reference internal" href="../glossary/o.html#term-object-format"><em class="xref std std-term">object format</em></a> need not provide a
<a class="reference internal" href="../glossary/f.html#term-forward-method"><em class="xref std std-term">forward method</em></a> or an <a class="reference internal" href="../glossary/i.html#term-is-forwarded-method"><em class="xref std std-term">is-forwarded method</em></a>.</li>
<li>Blocks must belong to an <a class="reference internal" href="../glossary/o.html#term-object-format"><em class="xref std std-term">object format</em></a>, but this may not be
a format of variant auto-header.</li>
</ul>
</div>
<div class="section" id="snc-introspection">
<span id="index-2"></span><h2>13.2. SNC introspection<a class="headerlink" href="#snc-introspection" title="Permalink to this headline"></a></h2>
<div class="highlight-c"><div class="highlight"><pre><span class="cp">#include &quot;mpscsnc.h&quot;</span>
</pre></div>
</div>
<dl class="function">
<dt id="mps_class_snc">
<a class="reference internal" href="../topic/pool.html#mps_class_t" title="mps_class_t">mps_class_t</a> <tt class="descname">mps_class_snc</tt><big>(</big>void<big>)</big><a class="headerlink" href="#mps_class_snc" title="Permalink to this definition"></a></dt>
<dd><p>Return the <a class="reference internal" href="../glossary/p.html#term-pool-class"><em class="xref std std-term">pool class</em></a> for an SNC (Stack No Check)
<a class="reference internal" href="../glossary/p.html#term-pool"><em class="xref std std-term">pool</em></a>.</p>
<p>When creating an SNC pool, <a class="reference internal" href="../topic/pool.html#mps_pool_create_k" title="mps_pool_create_k"><tt class="xref c c-func docutils literal"><span class="pre">mps_pool_create_k()</span></tt></a> requires one
<a class="reference internal" href="../glossary/k.html#term-keyword-argument"><em class="xref std std-term">keyword argument</em></a>:</p>
<ul class="simple">
<li><tt class="xref c c-macro docutils literal"><span class="pre">MPS_KEY_FORMAT</span></tt> (type <a class="reference internal" href="../topic/format.html#mps_fmt_t" title="mps_fmt_t"><tt class="xref c c-type docutils literal"><span class="pre">mps_fmt_t</span></tt></a>) specifies
the <a class="reference internal" href="../glossary/o.html#term-object-format"><em class="xref std std-term">object format</em></a> for the objects allocated in the pool.
The format must provide a <a class="reference internal" href="../glossary/s.html#term-scan-method"><em class="xref std std-term">scan method</em></a>, a <a class="reference internal" href="../glossary/s.html#term-skip-method"><em class="xref std std-term">skip
method</em></a>, and a <a class="reference internal" href="../glossary/p.html#term-padding-method"><em class="xref std std-term">padding method</em></a>.</li>
</ul>
<p>For example:</p>
<div class="highlight-c"><div class="highlight"><pre><span class="n">MPS_ARGS_BEGIN</span><span class="p">(</span><span class="n">args</span><span class="p">)</span> <span class="p">{</span>
<span class="n">MPS_ARGS_ADD</span><span class="p">(</span><span class="n">args</span><span class="p">,</span> <span class="n">MPS_KEY_FORMAT</span><span class="p">,</span> <span class="n">fmt</span><span class="p">);</span>
<span class="n">MPS_ARGS_DONE</span><span class="p">(</span><span class="n">args</span><span class="p">);</span>
<span class="n">res</span> <span class="o">=</span> <span class="n">mps_pool_create_k</span><span class="p">(</span><span class="o">&amp;</span><span class="n">pool</span><span class="p">,</span> <span class="n">arena</span><span class="p">,</span> <span class="n">mps_class_snc</span><span class="p">(),</span> <span class="n">args</span><span class="p">);</span>
<span class="p">}</span> <span class="n">MPS_ARGS_END</span><span class="p">(</span><span class="n">args</span><span class="p">);</span>
</pre></div>
</div>
<div class="admonition-deprecated admonition">
<p class="first admonition-title">Deprecated</p>
<p>starting with version 1.112.</p>
<p>When using <a class="reference internal" href="../topic/pool.html#mps_pool_create" title="mps_pool_create"><tt class="xref c c-func docutils literal"><span class="pre">mps_pool_create()</span></tt></a>, pass the format like
this:</p>
<div class="last highlight-c"><div class="highlight"><pre><span class="n">mps_res_t</span> <span class="n">mps_pool_create</span><span class="p">(</span><span class="n">mps_pool_t</span> <span class="o">*</span><span class="n">pool_o</span><span class="p">,</span> <span class="n">mps_arena_t</span> <span class="n">arena</span><span class="p">,</span>
<span class="n">mps_class_t</span> <span class="n">mps_class_snc</span><span class="p">(),</span>
<span class="n">mps_fmt_t</span> <span class="n">fmt</span><span class="p">)</span>
</pre></div>
</div>
</div>
<p>When creating an <a class="reference internal" href="../glossary/a.html#term-allocation-point"><em class="xref std std-term">allocation point</em></a> on an SNC pool,
<a class="reference internal" href="../topic/allocation.html#mps_ap_create_k" title="mps_ap_create_k"><tt class="xref c c-func docutils literal"><span class="pre">mps_ap_create_k()</span></tt></a> requires one keyword argument:</p>
<ul class="simple">
<li><tt class="xref c c-macro docutils literal"><span class="pre">MPS_KEY_RANK</span></tt> (type <a class="reference internal" href="../topic/root.html#mps_rank_t" title="mps_rank_t"><tt class="xref c c-type docutils literal"><span class="pre">mps_rank_t</span></tt></a>) specifies
the <a class="reference internal" href="../glossary/r.html#term-rank"><em class="xref std std-term">rank</em></a> of references in objects allocated on this
allocation point. It must be <a class="reference internal" href="../topic/root.html#mps_rank_exact" title="mps_rank_exact"><tt class="xref c c-func docutils literal"><span class="pre">mps_rank_exact()</span></tt></a>.</li>
</ul>
<p>For example:</p>
<div class="highlight-c"><div class="highlight"><pre><span class="n">MPS_ARGS_BEGIN</span><span class="p">(</span><span class="n">args</span><span class="p">)</span> <span class="p">{</span>
<span class="n">MPS_ARGS_ADD</span><span class="p">(</span><span class="n">args</span><span class="p">,</span> <span class="n">MPS_KEY_RANK</span><span class="p">,</span> <span class="n">mps_rank_exact</span><span class="p">());</span>
<span class="n">MPS_ARGS_DONE</span><span class="p">(</span><span class="n">args</span><span class="p">);</span>
<span class="n">res</span> <span class="o">=</span> <span class="n">mps_ap_create_k</span><span class="p">(</span><span class="o">&amp;</span><span class="n">ap</span><span class="p">,</span> <span class="n">awl_pool</span><span class="p">,</span> <span class="n">args</span><span class="p">);</span>
<span class="p">}</span> <span class="n">MPS_ARGS_END</span><span class="p">(</span><span class="n">args</span><span class="p">);</span>
</pre></div>
</div>
<div class="admonition-deprecated admonition">
<p class="first admonition-title">Deprecated</p>
<p>starting with version 1.112.</p>
<p>When using <a class="reference internal" href="../topic/allocation.html#mps_ap_create" title="mps_ap_create"><tt class="xref c c-func docutils literal"><span class="pre">mps_ap_create()</span></tt></a>, pass the rank like this:</p>
<div class="last highlight-c"><div class="highlight"><pre><span class="n">mps_res_t</span> <span class="n">mps_ap_create</span><span class="p">(</span><span class="n">mps_ap_t</span> <span class="o">*</span><span class="n">ap_o</span><span class="p">,</span> <span class="n">mps_pool_t</span> <span class="n">pool</span><span class="p">,</span>
<span class="n">mps_rank_t</span> <span class="n">rank</span><span class="p">)</span>
</pre></div>
</div>
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<h3><a href="../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">13. SNC (Stack No Checking)</a><ul>
<li><a class="reference internal" href="#snc-properties">13.1. SNC properties</a></li>
<li><a class="reference internal" href="#snc-introspection">13.2. SNC introspection</a></li>
</ul>
</li>
</ul>
<h4>Previous topic</h4>
<p class="topless"><a href="mvt.html"
title="previous chapter">12. MVT (Manual Variable Temporal)</a></p>
<h4>Next topic</h4>
<p class="topless"><a href="../design/index.html"
title="next chapter">Design</a></p><h4>Downloads</h4>
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<a href="http://www.ravenbrook.com/project/mps/release/1.111.0/">MPS Kit release 1.111.0</a><br>
<a href="http://www.ravenbrook.com/project/mps/release/">All MPS Kit releases</a>
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<h4>Issues</h4>
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<a href="http://www.ravenbrook.com/project/mps/issue/?action=list&amp;view=status%3dopen&amp;display=Job:Priority:Title&amp;sort=Priority">Known issues</a><br>
<a href="http://www.ravenbrook.com/project/mps/issue/?action=fixed&release_fixed=1.111.0">Issues fixed in release 1.111.0</a>
</p><h4>Contact us</h4>
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