snapshot_lesson


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#!/bin/sh
# Hacky little helper called from edit/ and sandbox/ apps to save a snapshot
# of lesson/ using git.
set -e

test -d lesson/.git || exit 0  # give up if it's not a git repo

cd lesson
# explicitly say '--all' for git 1.9
git add --all .
# bug in git: git diff -q messes up --exit-code
git diff HEAD --exit-code >/dev/null || git commit -a -m . >/dev/null
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<span class="Comment">//: Reclaiming memory when it's no longer used.</span>
<span class="Comment">//: The top of the address layer has the complete life cycle of memory.</span>

<span class="Delimiter">:(scenario new_reclaim)</span>
def main [
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:number  <span class="Comment"># because 1 will get reset during abandon below</span>
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># abandon</span>
  <span class="Constant">3</span>:address:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type  <span class="Comment"># must be same size as abandoned memory to reuse</span>
  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>:address:number
  <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:number<span class="Delimiter">,</span> <span class="Constant">4</span>:number
]
<span class="Comment"># both allocations should have returned the same address</span>
<span class="traceContains">+mem: storing 1 in location 5</span>

<span class="Delimiter">:(before &quot;End Decrement Refcount(old_address, payload_type, payload_size)&quot;)</span>
<span class="Normal">if</span> <span class="Delimiter">(</span>old_refcount == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;automatically abandoning &quot;</span> &lt;&lt; old_address &lt;&lt; end<span class="Delimiter">();</span>
  abandon<span class="Delimiter">(</span>old_address<span class="Delimiter">,</span> payload_type<span class="Delimiter">,</span> payload_size<span class="Delimiter">);</span>
<span class="Delimiter">}</span>

<span class="Comment">//: When abandoning addresses we'll save them to a 'free list', segregated by size.</span>

<span class="Delimiter">:(before &quot;End routine Fields&quot;)</span>
map&lt;<span class="Normal">int</span><span class="Delimiter">,</span> <span class="Normal">int</span>&gt; free_list<span class="Delimiter">;</span>

<span class="Delimiter">:(code)</span>
<span class="Normal">void</span> abandon<span class="Delimiter">(</span><span class="Normal">int</span> address<span class="Delimiter">,</span> <span class="Normal">const</span> type_tree* payload_type<span class="Delimiter">,</span> <span class="Normal">int</span> payload_size<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;abandon&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;updating refcounts inside &quot;</span> &lt;&lt; address &lt;&lt; <span class="Constant">&quot;: &quot;</span> &lt;&lt; to_string<span class="Delimiter">(</span>payload_type<span class="Delimiter">)</span> &lt;&lt; end<span class="Delimiter">();</span>
<span class="CommentedCode">//?   Total_free += size;</span>
<span class="CommentedCode">//?   Num_free++;</span>
<span class="CommentedCode">//?   cerr &lt;&lt; &quot;abandon: &quot; &lt;&lt; size &lt;&lt; '\n';</span>
  <span class="Comment">// decrement any contained refcounts</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>payload_type<span class="Delimiter">-&gt;</span>name == <span class="Constant">&quot;array&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
    reagent element<span class="Delimiter">;</span>
    element<span class="Delimiter">.</span>type = copy_array_element<span class="Delimiter">(</span>payload_type<span class="Delimiter">);</span>
    <span class="Normal">int</span> array_length = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> address+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">);</span>
    assert<span class="Delimiter">(</span>element<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>name != <span class="Constant">&quot;array&quot;</span><span class="Delimiter">);</span>
    <span class="Normal">int</span> element_size = size_of<span class="Delimiter">(</span>element<span class="Delimiter">);</span>
    <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; array_length<span class="Delimiter">;</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
      element<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>address + <span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span> + <span class="Comment">/*</span><span class="Comment">skip array length</span><span class="Comment">*/</span><span class="Constant">1</span> + i*element_size<span class="Delimiter">);</span>
      decrement_any_refcounts<span class="Delimiter">(</span>element<span class="Delimiter">);</span>
    <span class="Delimiter">}</span>
  <span class="Delimiter">}</span>
  <span class="Normal">else</span> <span class="Normal">if</span> <span class="Delimiter">(</span>is_mu_container<span class="Delimiter">(</span>payload_type<span class="Delimiter">)</span> || is_mu_exclusive_container<span class="Delimiter">(</span>payload_type<span class="Delimiter">))</span> <span class="Delimiter">{</span>
    reagent tmp<span class="Delimiter">;</span>
    tmp<span class="Delimiter">.</span>type = <span class="Normal">new</span> type_tree<span class="Delimiter">(</span>*payload_type<span class="Delimiter">);</span>
    tmp<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>address + <span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">);</span>
    decrement_any_refcounts<span class="Delimiter">(</span>tmp<span class="Delimiter">);</span>
  <span class="Delimiter">}</span>
  <span class="Comment">// clear memory</span>
  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> curr = address<span class="Delimiter">;</span> curr &lt; address+payload_size<span class="Delimiter">;</span> ++curr<span class="Delimiter">)</span>
    put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> curr<span class="Delimiter">,</span> <span class="Constant">0</span><span class="Delimiter">);</span>
  <span class="Comment">// append existing free list to address</span>
  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;abandon&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;saving &quot;</span> &lt;&lt; address &lt;&lt; <span class="Constant">&quot; in free-list of size &quot;</span> &lt;&lt; payload_size &lt;&lt; end<span class="Delimiter">();</span>
  put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> address<span class="Delimiter">,</span> get_or_insert<span class="Delimiter">(</span>Current_routine<span class="Delimiter">-&gt;</span>free_list<span class="Delimiter">,</span> payload_size<span class="Delimiter">));</span>
  put<span class="Delimiter">(</span>Current_routine<span class="Delimiter">-&gt;</span>free_list<span class="Delimiter">,</span> payload_size<span class="Delimiter">,</span> address<span class="Delimiter">);</span>
<span class="Delimiter">}</span>

<span class="Delimiter">:(after &quot;Allocate Special-cases&quot;)</span>
<span class="Normal">if</span> <span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Current_routine<span class="Delimiter">-&gt;</span>free_list<span class="Delimiter">,</span> size<span class="Delimiter">))</span> <span class="Delimiter">{</span>
  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;abandon&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;picking up space from free-list of size &quot;</span> &lt;&lt; size &lt;&lt; end<span class="Delimiter">();</span>
  <span class="Normal">int</span> result = get_or_insert<span class="Delimiter">(</span>Current_routine<span class="Delimiter">-&gt;</span>free_list<span class="Delimiter">,</span> size<span class="Delimiter">);</span>
  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;new alloc from free list: &quot;</span> &lt;&lt; result &lt;&lt; end<span class="Delimiter">();</span>
  put<span class="Delimiter">(</span>Current_routine<span class="Delimiter">-&gt;</span>free_list<span class="Delimiter">,</span> size<span class="Delimiter">,</span> get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> result<span class="Delimiter">));</span>
  put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> result<span class="Delimiter">,</span> <span class="Constant">0</span><span class="Delimiter">);</span>
  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> curr = result<span class="Delimiter">;</span> curr &lt; result+size<span class="Delimiter">;</span> ++curr<span class="Delimiter">)</span> <span class="Delimiter">{</span>
    <span class="Normal">if</span> <span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> curr<span class="Delimiter">)</span> != <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
      raise &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;memory in free list was not zeroed out: &quot;</span> &lt;&lt; curr &lt;&lt; <span class="Constant">'/'</span> &lt;&lt; result &lt;&lt; <span class="Constant">&quot;; somebody wrote to us after free!!!</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
      <span class="Identifier">break</span><span class="Delimiter">;</span>  <span class="Comment">// always fatal</span>
    <span class="Delimiter">}</span>
  <span class="Delimiter">}</span>
  <span class="Identifier">return</span> result<span class="Delimiter">;</span>
<span class="Delimiter">}</span>

<span class="Delimiter">:(scenario new_differing_size_no_reclaim)</span>
def main [
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:number
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># abandon</span>
  <span class="Constant">3</span>:address:array:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type<span class="Delimiter">,</span> <span class="Constant">2</span>  <span class="Comment"># different size</span>
  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>:address:array:number
  <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:number<span class="Delimiter">,</span> <span class="Constant">4</span>:number
]
<span class="Comment"># no reuse</span>
<span class="traceContains">+mem: storing 0 in location 5</span>

<span class="Delimiter">:(scenario new_reclaim_array)</span>
def main [
  <span class="Constant">1</span>:address:array:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type<span class="Delimiter">,</span> <span class="Constant">2</span>
  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:array:number
  <span class="Constant">1</span>:address:array:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># abandon</span>
  <span class="Constant">3</span>:address:array:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type<span class="Delimiter">,</span> <span class="Constant">2</span>  <span class="Comment"># same size</span>
  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>:address:array:number
  <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:number<span class="Delimiter">,</span> <span class="Constant">4</span>:number
]
<span class="Comment"># both calls to new returned identical addresses</span>
<span class="traceContains">+mem: storing 1 in location 5</span>

<span class="Delimiter">:(scenario abandon_on_overwrite)</span>
def main [
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
  <span class="Comment"># over-writing one allocation with another</span>
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
]
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;number&quot;)} &lt;- new {number: &quot;type&quot;}</span>
<span class="traceContains">+mem: incrementing refcount of 1000: 0 -&gt; 1</span>
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;number&quot;)} &lt;- new {number: &quot;type&quot;}</span>
<span class="traceContains">+mem: automatically abandoning 1000</span>

<span class="Delimiter">:(scenario abandon_after_call)</span>
def main [
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
  <span class="Comment"># passing in addresses to recipes increments refcount</span>
  foo <span class="Constant">1</span>:address:number
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
]
def foo [
  <span class="Constant">2</span>:address:number<span class="Special"> &lt;- </span>next-ingredient
  <span class="Comment"># return does NOT yet decrement refcount; memory must be explicitly managed</span>
  <span class="Constant">2</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
]
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;number&quot;)} &lt;- new {number: &quot;type&quot;}</span>
<span class="traceContains">+mem: incrementing refcount of 1000: 0 -&gt; 1</span>
<span class="traceContains">+run: foo {1: (&quot;address&quot; &quot;number&quot;)}</span>
<span class="Comment"># leave ambiguous precisely when the next increment happens; a later layer</span>
<span class="Comment"># will mess with that</span>
<span class="traceContains">+mem: incrementing refcount of 1000: 1 -&gt; 2</span>
<span class="traceContains">+run: {2: (&quot;address&quot; &quot;number&quot;)} &lt;- copy {0: &quot;literal&quot;}</span>
<span class="traceContains">+mem: decrementing refcount of 1000: 2 -&gt; 1</span>
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;number&quot;)} &lt;- copy {0: &quot;literal&quot;}</span>
<span class="traceContains">+mem: decrementing refcount of 1000: 1 -&gt; 0</span>
<span class="traceContains">+mem: automatically abandoning 1000</span>

<span class="Delimiter">:(scenario abandon_on_overwrite_array)</span>
def main [
  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">30</span>
  <span class="Comment"># allocate an array</span>
  <span class="Constant">10</span>:address:array:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type<span class="Delimiter">,</span> <span class="Constant">20</span>
  <span class="Constant">11</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">10</span>:address:array:number  <span class="Comment"># doesn't increment refcount</span>
  <span class="Comment"># allocate another array in its place, implicitly freeing the previous allocation</span>
  <span class="Constant">10</span>:address:array:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type<span class="Delimiter">,</span> <span class="Constant">25</span>
]
<span class="traceContains">+run: {10: (&quot;address&quot; &quot;array&quot; &quot;number&quot;)} &lt;- new {number: &quot;type&quot;}, {25: &quot;literal&quot;}</span>
<span class="Comment"># abandoned array is of old size (20, not 25)</span>
<span class="traceContains">+abandon: saving 1000 in free-list of size 22</span>

<span class="Delimiter">:(scenario refcounts_abandon_address_in_container)</span>
<span class="Comment"># container containing an address</span>
container foo [
  <span class="Normal">x</span>:address:number
]
def main [
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
  <span class="Constant">2</span>:address:foo<span class="Special"> &lt;- </span><span class="Normal">new</span> foo:type
  *<span class="Constant">2</span>:address:foo<span class="Special"> &lt;- </span>put *<span class="Constant">2</span>:address:foo<span class="Delimiter">,</span> x:offset<span class="Delimiter">,</span> <span class="Constant">1</span>:address:number
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Constant">2</span>:address:foo<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
]
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;number&quot;)} &lt;- new {number: &quot;type&quot;}</span>
<span class="traceContains">+mem: incrementing refcount of 1000: 0 -&gt; 1</span>
<span class="traceContains">+run: {2: (&quot;address&quot; &quot;foo&quot;)} &lt;- new {foo: &quot;type&quot;}</span>
<span class="traceContains">+mem: incrementing refcount of 1002: 0 -&gt; 1</span>
<span class="traceContains">+run: {2: (&quot;address&quot; &quot;foo&quot;), &quot;lookup&quot;: ()} &lt;- put {2: (&quot;address&quot; &quot;foo&quot;), &quot;lookup&quot;: ()}, {x: &quot;offset&quot;}, {1: (&quot;address&quot; &quot;number&quot;)}</span>
<span class="traceContains">+mem: incrementing refcount of 1000: 1 -&gt; 2</span>
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;number&quot;)} &lt;- copy {0: &quot;literal&quot;}</span>
<span class="traceContains">+mem: decrementing refcount of 1000: 2 -&gt; 1</span>
<span class="traceContains">+run: {2: (&quot;address&quot; &quot;foo&quot;)} &lt;- copy {0: &quot;literal&quot;}</span>
<span class="Comment"># start abandoning container containing address</span>
<span class="traceContains">+mem: decrementing refcount of 1002: 1 -&gt; 0</span>
<span class="Comment"># nested abandon</span>
<span class="traceContains">+mem: decrementing refcount of 1000: 1 -&gt; 0</span>
<span class="traceContains">+abandon: saving 1000 in free-list of size 2</span>
<span class="Comment"># actually abandon the container containing address</span>
<span class="traceContains">+abandon: saving 1002 in free-list of size 2</span>

<span class="Comment"># todo: move past dilated reagent</span>
<span class="Delimiter">:(scenario refcounts_abandon_address_in_array)</span>
def main [
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
  <span class="Constant">2</span>:address:array:address:number<span class="Special"> &lt;- </span><span class="Normal">new</span> <span class="Delimiter">{(</span>address number<span class="Delimiter">)</span>: type<span class="Delimiter">},</span> <span class="Constant">3</span>
  *<span class="Constant">2</span>:address:array:address:number<span class="Special"> &lt;- </span>put-index *<span class="Constant">2</span>:address:array:address:number<span class="Delimiter">,</span> <span class="Constant">1</span><span class="Delimiter">,</span> <span class="Constant">1</span>:address:number
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Constant">2</span>:address:array:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
]
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;number&quot;)} &lt;- new {number: &quot;type&quot;}</span>
<span class="traceContains">+mem: incrementing refcount of 1000: 0 -&gt; 1</span>
<span class="traceContains">+run: {2: (&quot;address&quot; &quot;array&quot; &quot;address&quot; &quot;number&quot;), &quot;lookup&quot;: ()} &lt;- put-index {2: (&quot;address&quot; &quot;array&quot; &quot;address&quot; &quot;number&quot;), &quot;lookup&quot;: ()}, {1: &quot;literal&quot;}, {1: (&quot;address&quot; &quot;number&quot;)}</span>
<span class="traceContains">+mem: incrementing refcount of 1000: 1 -&gt; 2</span>
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;number&quot;)} &lt;- copy {0: &quot;literal&quot;}</span>
<span class="traceContains">+mem: decrementing refcount of 1000: 2 -&gt; 1</span>
<span class="traceContains">+run: {2: (&quot;address&quot; &quot;array&quot; &quot;address&quot; &quot;number&quot;)} &lt;- copy {0: &quot;literal&quot;}</span>
<span class="Comment"># nested abandon</span>
<span class="traceContains">+mem: decrementing refcount of 1000: 1 -&gt; 0</span>
<span class="traceContains">+abandon: saving 1000 in free-list of size 2</span>

<span class="Delimiter">:(scenario refcounts_abandon_address_in_container_in_array)</span>
<span class="Comment"># container containing an address</span>
container foo [
  <span class="Normal">x</span>:address:number
]
def main [
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
  <span class="Constant">2</span>:address:array:foo<span class="Special"> &lt;- </span><span class="Normal">new</span> foo:type<span class="Delimiter">,</span> <span class="Constant">3</span>
  <span class="Constant">3</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">1</span>:address:number
  *<span class="Constant">2</span>:address:array:foo<span class="Special"> &lt;- </span>put-index *<span class="Constant">2</span>:address:array:foo<span class="Delimiter">,</span> <span class="Constant">1</span><span class="Delimiter">,</span> <span class="Constant">3</span>:foo
  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Constant">3</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">0</span>
  <span class="Constant">2</span>:address:array:foo<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
]
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;number&quot;)} &lt;- new {number: &quot;type&quot;}</span>
<span class="traceContains">+mem: incrementing refcount of 1000: 0 -&gt; 1</span>
<span class="traceContains">+run: {3: &quot;foo&quot;} &lt;- merge {1: (&quot;address&quot; &quot;number&quot;)}</span>
<span class="traceContains">+mem: incrementing refcount of 1000: 1 -&gt; 2</span>
<span class="traceContains">+run: {2: (&quot;address&quot; &quot;array&quot; &quot;foo&quot;), &quot;lookup&quot;: ()} &lt;- put-index {2: (&quot;address&quot; &quot;array&quot; &quot;foo&quot;), &quot;lookup&quot;: ()}, {1: &quot;literal&quot;}, {3: &quot;foo&quot;}</span>
<span class="traceContains">+mem: incrementing refcount of 1000: 2 -&gt; 3</span>
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;number&quot;)} &lt;- copy {0: &quot;literal&quot;}</span>
<span class="traceContains">+mem: decrementing refcount of 1000: 3 -&gt; 2</span>
<span class="traceContains">+run: {3: &quot;foo&quot;} &lt;- merge {0: &quot;literal&quot;}</span>
<span class="traceContains">+mem: decrementing refcount of 1000: 2 -&gt; 1</span>
<span class="traceContains">+run: {2: (&quot;address&quot; &quot;array&quot; &quot;foo&quot;)} &lt;- copy {0: &quot;literal&quot;}</span>
<span class="Comment"># nested abandon</span>
<span class="traceContains">+mem: decrementing refcount of 1000: 1 -&gt; 0</span>
<span class="traceContains">+abandon: saving 1000 in free-list of size 2</span>
</pre>
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