Improved `all-run.sh` and `readme2index.sh` so that certain command line options (e.g., -p, -P, -u, -U ...) are only passed along to other tools if they are given on the command line. all-run.sh VERSION changed from "1.1.1 2024-01-19" to "1.1.2 2024-01-20", readme2index.sh VERSION changed from "1.1 2024-01-16" to "1.1.1 2024-01-20". Added `quick-readme2index.sh` that only calls `readme2index.sh` if the `index.html` is not a non-empty file, or of either `.winner.json` and/or `README.md` is newer than `index.html`. Updated all `index.html` files because the the file contains a comment that includes the newly modified readme2index.sh VERSION.
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<meta charset="utf-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
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<title>1984/mullender</title>
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<meta name="description" content="1984 IOCCC winner mullender">
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<meta name="keywords" content="IOCCC, 1984, IOCCC 1984, IOCCC winner, mullender">
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<div class="header">
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<img src="/temp-test-ioccc/png/ioccc.png" alt="IOCCC image by Matt Zucker" width=300 height=110>
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<h1>The International Obfuscated C Code Contest</h1>
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<h2>1984/mullender</h2>
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<div class="topnav">
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<a class="Left" href="../laman/index.html">← laman</a>
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<a class="Left" href="../index.html">↑ 1984 ↑</a>
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<a class="Left Disabled" href="#">last entry</a>
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<a class="Right" href="#inventory">Inventory</a>
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<a href="#content">Jump to contents</a>
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<div class="sidenav">
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<a href="/temp-test-ioccc/index.html">IOCCC Home</a>
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<a href="/temp-test-ioccc/years.html">Winning Entries</a>
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<a href="/temp-test-ioccc/winners.html">People who have won</a>
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</div>
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<hr>
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<div class="sidenav">
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<a href="/temp-test-ioccc/news.html">IOCCC News</a>
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<a href="/temp-test-ioccc/faq.html#submit">How to enter the IOCCC</a>
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<a href="/temp-test-ioccc/faq.html">FAQ</a>
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</div>
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<hr>
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<div class="sidenav">
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<a href="/temp-test-ioccc/bugs.html">Bugs & (mis)features</a>
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<a href="/temp-test-ioccc/faq.html#fix_a_winner">Fixing IOCCC winners</a>
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<a href="/temp-test-ioccc/faq.html#fix_web_site">Fixing the web site</a>
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<a href="/temp-test-ioccc/faq.html#fix_author">Fixing winner info</a>
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<a href="/temp-test-ioccc/thanks-for-help.html">Thanks for the help</a>
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</div>
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<hr>
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<div class="sidenav">
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<a href="/temp-test-ioccc/judges.html">The IOCCC Judges</a>
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<a href="/temp-test-ioccc/contact.html">Contacting the IOCCC</a>
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</div>
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<hr>
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<a href="#top">Jump to top</a>
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<p><a name="author"><strong>Authors:</strong></a> <br><br>Name: <a
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href="/temp-test-ioccc/winners.html#Robbert_van_Renesse">Robbert van
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Renesse</a><br> Location: <a
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href="/temp-test-ioccc/location.html#US">US</a> <br><br>Name: <a
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href="/temp-test-ioccc/winners.html#Sjoerd_Mullender">Sjoerd
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Mullender</a><br> Location: <a
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href="/temp-test-ioccc/location.html#NL">NL</a></p>
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<h2 id="to-build">To build:</h2>
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<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="fu">make</span> alt</span></code></pre></div>
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<p>NOTE: the original code will not work on any system other than <a
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href="https://en.wikipedia.org/wiki/VAX-11">VAX-11</a> and <a
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href="https://en.wikipedia.org/wiki/PDP-11">PDP-11</a> and this is why
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we encourage you to use the alt version instead. See <a
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href="#original-code">original code</a> below for the original
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version.</p>
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<h3 id="bugs-and-misfeatures">Bugs and (Mis)features:</h3>
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<p>The current status of this entry is:</p>
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<pre><code>STATUS: INABIAF - please **DO NOT** fix</code></pre>
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<p>For more detailed information see <a
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href="/bugs.md#1984-mullender">1984 mullender in bugs.md</a>.</p>
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<h2 id="to-use">To use:</h2>
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<div class="sourceCode" id="cb3"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./mullender.alt</span> <span class="pp">[</span><span class="ss">microseconds</span><span class="pp">]</span></span></code></pre></div>
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<p>Hit ctrl-c/intr to exit the program.</p>
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<p>The default microseconds is 190000 as this is approximately how long
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it slept in the original entry but it can be no lower than 5000 as any
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lower doesn’t work very well. This feature is so you can experiment with
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different speeds in between writes. It can be useful if your CPU is too
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fast :-)</p>
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<p>The author stated that the original version also had a delay but the
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difference is it required one to hit enter for it to print another line;
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the alt code will start over once it times out or if one hits a key.</p>
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<p>Note that the microseconds is argc and it uses <code>atoi()</code>
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which does NOT check for overflow!</p>
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<p>BTW: is there such a thing as too fast a CPU ? :-) Actually yes for
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certain code which is probably not as uncommon as you think :-).</p>
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<h2 id="try">Try:</h2>
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<div class="sourceCode" id="cb4"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./mullender.alt</span></span>
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<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a></span>
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<span id="cb4-3"><a href="#cb4-3" aria-hidden="true" tabindex="-1"></a><span class="ex">./mullender.alt</span> 5000 <span class="co"># wait for 5000 microseconds and see what happens</span></span>
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<span id="cb4-4"><a href="#cb4-4" aria-hidden="true" tabindex="-1"></a></span>
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<span id="cb4-5"><a href="#cb4-5" aria-hidden="true" tabindex="-1"></a><span class="ex">./mullender.alt</span> 20000 <span class="co"># wait for 20000 microseconds and see what happens</span></span>
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<span id="cb4-6"><a href="#cb4-6" aria-hidden="true" tabindex="-1"></a></span>
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<span id="cb4-7"><a href="#cb4-7" aria-hidden="true" tabindex="-1"></a><span class="ex">./mullender.alt</span> 100000 <span class="co"># wait for 100000 microseconds and see what happens</span></span></code></pre></div>
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<p>What happens if you hit enter after it reaches the end of the line?
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Why? What happens after some time of waiting?</p>
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<h2 id="original-code">Original code:</h2>
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<p>This original code will only execute correctly if your machine is a
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<a href="https://en.wikipedia.org/wiki/VAX-11">VAX-11</a> or <a
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href="https://en.wikipedia.org/wiki/PDP-11">PDP-11</a>. In the following
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years, 1985 on, machine dependent code was discouraged.</p>
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<h3 id="original-build">Original build:</h3>
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<div class="sourceCode" id="cb5"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a><span class="fu">make</span> all</span></code></pre></div>
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<h3 id="original-use">Original use:</h3>
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<div class="sourceCode" id="cb6"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./mullender</span></span></code></pre></div>
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<h2 id="judges-remarks">Judges’ remarks:</h2>
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<p>Without question, this C program is the one of the most obfuscated C
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program that has ever been received! Like all great contest entries, it
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resulted in a change of rules for the following year. To prevent a flood
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of similar programs, the rules were changed, requesting non-machine
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specific code.</p>
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<p>This program was selected for the 1987 t-shirt collection.</p>
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<p>The C startup routine (via <a
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href="https://en.wikipedia.org/wiki/Crt0">crt0.o</a>) transfers control
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to a location named <code>main</code>. In this case, <code>main</code>
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just happens to be in the data area. The array of <code>short</code>s,
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which has been further obfuscated by use of different data types, just
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happens to form a meaningful set of <a
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href="https://en.wikipedia.org/wiki/PDP-11">PDP-11</a> and <a
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href="https://en.wikipedia.org/wiki/VAX">VAX</a> instructions.</p>
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<p>The first word is a <a
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href="https://en.wikipedia.org/wiki/PDP-11">PDP-11</a> branch
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instruction that branches to the rest of the <a
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href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>
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code.</p>
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<p>On the VAX <code>main</code> is called with the <a
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href="https://jcsites.juniata.edu/faculty/rhodes/org/instr.htm#CALLS">calls
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instruction</a> which uses the first word of the subroutine as a mask of
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registers to be saved. So on the VAX the first word can be anything. The
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real VAX code starts with the second word.</p>
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<p>This small program makes direct calls to the <code>write()</code>
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Unix system call to produce a message on the screen. Can you guess what
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is printed? We knew you couldn’t! :-)</p>
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<p>What happens if you hit enter after it writes a line of output?</p>
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<p>BTW: to this day, 2023, this remains one of my (Landon Curt Noll’s)
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all time favorite entries!</p>
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<h3 id="gentab.c">gentab.c</h3>
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<p>In 2023 remarks were discovered from <a
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href="/winners.html#Sjoerd_Mullender">Sjoerd Mullender</a>, one of the
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authors, and so was the program that was used by the authors to generate
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the array that he referred to. Because <a href="a.out.h">a.out.h</a>,
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which <a href="gentab.c">gentab.c</a> uses, is not available in all
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systems (like macOS) and more importantly because we wanted it to be as
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close to as the original as possible we used a copy of <a
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href="https://raw.githubusercontent.com/dspinellis/unix-history-repo/Research-Release/usr/include/a.out.h"
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class="uri">https://raw.githubusercontent.com/dspinellis/unix-history-repo/Research-Release/usr/include/a.out.h</a>
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in the <em>fabulous</em> <a
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href="https://github.com/dspinellis/unix-history-repo/tree/Research-Release">Unix
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History Repo</a>.</p>
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<h3 id="gentab-build">gentab build:</h3>
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<p><code>gentab.c</code> can be built like:</p>
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<div class="sourceCode" id="cb7"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb7-1"><a href="#cb7-1" aria-hidden="true" tabindex="-1"></a><span class="fu">make</span> gentab</span></code></pre></div>
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<h3 id="gentab-use">gentab use:</h3>
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<div class="sourceCode" id="cb8"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./gentab</span> file</span></code></pre></div>
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<h3 id="gentab-try">gentab try:</h3>
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<div class="sourceCode" id="cb9"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb9-1"><a href="#cb9-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./gentab</span> gentab <span class="op">></span> g.c</span></code></pre></div>
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<p>NOTE: it is highly unlikely that you will be able to run the output
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of <code>gentab</code> but it should at least compile.</p>
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<h2 id="authors-remarks">Author’s remarks:</h2>
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<h3 id="notes-from-the-judges">Notes from the judges:</h3>
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<p>These remarks, found at <a
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href="https://lainsystems.com/posts/exploring-mullender-dot-c/">https://lainsystems.com/posts/exploring-mullender-dot-c/</a>,
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were provided by Sjoerd Mullender years later. We thank the author of
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the article for the quote! For a more detailed analysis, taken from the
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book Obfuscated C and Other Mysteries, see below. We hope that this is
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okay with the author of the book. Considering that the analysis is
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entirely the authors’ comments we don’t think this will be a problem.
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Unfortunately the excerpt was PDF and it did not copy paste well. We had
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to go back and forth to type so it’s possible he made a typo though he
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also fixed some typos found in the extract. As for the other
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comments:</p>
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<h3 id="remarks-from-the-author">Remarks from the author:</h3>
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<p>I have never known a lot about the <a
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href="https://en.wikipedia.org/wiki/VAX">VAX</a> <a
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href="https://en.wikipedia.org/wiki/Assembly_language">assembly</a>, so
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we used the C compiler to create the VAX code. We didn’t write it
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ourselves from scratch as we did with the <a
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href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>
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code. This is the reason why the <a
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href="https://en.wikipedia.org/wiki/VAX">VAX</a> code is more complex,
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including the extra data after the <a
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href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>
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code.</p>
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<p>Robbert and I were students at the <a href="https://vu.nl/en">VU
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(Free University in Amsterdam)</a> at the time (mathematics with CS as
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our major since there was no CS curriculum when we started). We had an
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assignment to create a pair of programs for the computer networks
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course. The programs were supposed to send data reliably from one
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program to the other over an unreliable channel. This channel was
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simulated with a pair of <a
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||
href="https://en.wikipedia.org/wiki/Pipeline_(software)">pipes</a>.</p>
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<p>We decided for fun to create an <a
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href="https://en.wikipedia.org/wiki/Obfuscation_(software)">obfuscated</a>
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set of programs, only for the <a
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||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>,
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||
to do this, but circumventing the channel (i.e. cheating, hence the
|
||
needed obfuscation.). Our programs worked and we handed them in.</p>
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||
<p>Of course, the teacher had a good laugh and then rejected our
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submission. (We knew him well, so we could get away with this.)</p>
|
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<p>Then the <a href="https://www.ioccc.org">IOCCC</a> came along. I
|
||
don’t remember how we heard about it, but at the time there was a
|
||
world-wide messaging network Usenet where we read a bunch of newsgroups.
|
||
I’m sure it was <a
|
||
href="https://groups.google.com/g/net.lang.c/c/lx-TAuEyeRI/m/HdOOnNx6LC0J">announced
|
||
there</a> and we saw it.</p>
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||
<p>Since we had just recently created these <a
|
||
href="https://en.wikipedia.org/wiki/Obfuscation_(software)">obfuscated
|
||
programs</a>) we decided we could use the same technique for an
|
||
obfuscated C program. We upped the ante a bit by making it
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“portable”.</p>
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<p>To add to the <a
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href="https://en.wikipedia.org/wiki/Obfuscation_(software)">obfuscation</a>),
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we used different formats for the integers in the array: some in
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decimal, some in octal, some in hexadecimal, and when the value would
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fit, some as an ASCII character.</p>
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<p>The rest is history.</p>
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||
<p>Since this was the first contest, we hadn’t seen any old entries, nor
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had any of the other contestants. Of course we knew about
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<code>#define</code> and tricks you could do with that, but we didn’t
|
||
need that for this program. In fact, we made it as “standard” as
|
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possible. At the time there was this program called <code>cb</code> or C
|
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beautifier which would re-indent your program to make the layout look
|
||
better. Our program is idempotent under <code>cb</code>.</p>
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<h3 id="more-detailed-analysis">More detailed analysis</h3>
|
||
<p>When this program is compiled, the compiler places the array
|
||
somewhere in memory, just like it places any compiled code somewhere in
|
||
memory. Usually, the C startup code (<a
|
||
href="https://en.wikipedia.org/wiki/Crt0">crt0.o</a>) calls a routine
|
||
named <code>main()</code>. The loader fills in the address in the
|
||
startup code, but at least on the old systems where this program ran, it
|
||
doesn’t know that the <code>main()</code> in this program isn’t code but
|
||
data!</p>
|
||
<p>When the program is run, the C startup code transfers control to the
|
||
location <code>main</code>. The contents of the array just happen to be
|
||
machine instructions for both a <a
|
||
href="https://en.wikipedia.org/wiki/PDP-11">PDP-11</a> and a <a
|
||
href="https://en.wikipedia.org/wiki/VAX">VAX</a>.</p>
|
||
<p>On the <a href="https://en.wikipedia.org/wiki/VAX">VAX</a>, the
|
||
routine <code>main()</code> is called with the <code>calls</code>
|
||
instruction. This instruction uses the first (2-byte) <a
|
||
href="https://en.wikipedia.org/wiki/Word_(computer_architecture)">word</a>
|
||
of the called routine as a mask of <a
|
||
href="https://en.wikipedia.org/wiki/Processor_register">registers</a>
|
||
that are to be saved on the <a
|
||
href="https://en.wikipedia.org/wiki/Stack_(abstract_data_type)">stack</a>.
|
||
In other words, on the VAX the first word can be anything. On the <a
|
||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>,
|
||
the first word is a <a
|
||
href="https://en.wikipedia.org/wiki/Branch_(computer_science)">branch</a>
|
||
<a
|
||
href="https://en.wikipedia.org/wiki/Instruction_set_architecture#Instructions">instruction</a>
|
||
that branches over the VAX code. The PDP and VAX codes are thus
|
||
completely separate.</p>
|
||
<p>The <a
|
||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>
|
||
and <a href="https://en.wikipedia.org/wiki/VAX">VAX</a> codes implement
|
||
the same algorithm:</p>
|
||
<div class="sourceCode" id="cb10"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb10-1"><a href="#cb10-1" aria-hidden="true" tabindex="-1"></a> <span class="cf">for</span> <span class="op">(;;)</span> <span class="op">{</span></span>
|
||
<span id="cb10-2"><a href="#cb10-2" aria-hidden="true" tabindex="-1"></a> write<span class="op">(</span><span class="dv">1</span><span class="op">,</span> <span class="st">" :-)</span><span class="sc">\b\b\b\b</span><span class="st">"</span><span class="op">,</span> <span class="dv">9</span><span class="op">);</span></span>
|
||
<span id="cb10-3"><a href="#cb10-3" aria-hidden="true" tabindex="-1"></a> delay<span class="op">();</span></span>
|
||
<span id="cb10-4"><a href="#cb10-4" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span></code></pre></div>
|
||
<p>The result is that the symbols <code>:-)</code> move across the
|
||
screen. <code>delay</code> is implemented differently on the <a
|
||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>,
|
||
where we used a nonexistent system call (<code>sys 55</code>), and on
|
||
the <a href="https://en.wikipedia.org/wiki/VAX">VAX</a> where we used a
|
||
delay loop.</p>
|
||
<p>My co-author, Robbert, and I had earlier written a similar program
|
||
for an assignment on the <a
|
||
href="https://en.wikipedia.org/wiki/PDP-11">PDP-11</a>. <a
|
||
href="https://groups.google.com/g/net.lang.c/c/lx-TAuEyeRI/m/HdOOnNx6LC0J">Along
|
||
came</a> the first <a href="https://www.ioccc.org">Obfuscated C Code
|
||
Contest</a>, and we decided that we should write a program like this,
|
||
but make it run on two different <a
|
||
href="https://en.wikipedia.org/wiki/Computer_architecture">architectures</a>.</p>
|
||
<p>We didn’t think long about what the program should do, so it does
|
||
something very simple.</p>
|
||
<p>We started with writing the <a
|
||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>
|
||
code in assembly. We both knew <a
|
||
href="https://en.wikipedia.org/wiki/PDP-11">PDP-11</a> assembly so that
|
||
was no problem. The assembly code we came up with is as follows:</p>
|
||
<div class="sourceCode" id="cb11"><pre
|
||
class="sourceCode asm"><code class="sourceCode fasm"><span id="cb11-1"><a href="#cb11-1" aria-hidden="true" tabindex="-1"></a><span class="fu">pdp:</span></span>
|
||
<span id="cb11-2"><a href="#cb11-2" aria-hidden="true" tabindex="-1"></a> <span class="bu">mov</span> pc<span class="op">,</span>r4</span>
|
||
<span id="cb11-3"><a href="#cb11-3" aria-hidden="true" tabindex="-1"></a> tst <span class="op">-(</span>r4<span class="op">)</span></span>
|
||
<span id="cb11-4"><a href="#cb11-4" aria-hidden="true" tabindex="-1"></a> <span class="bu">sub</span> <span class="op">$</span><span class="bn">9</span><span class="op">,</span> r4</span>
|
||
<span id="cb11-5"><a href="#cb11-5" aria-hidden="true" tabindex="-1"></a> <span class="bu">mov</span> r4<span class="op">,</span><span class="fl">0</span><span class="bn">f</span></span>
|
||
<span id="cb11-6"><a href="#cb11-6" aria-hidden="true" tabindex="-1"></a> <span class="bu">mov</span> <span class="op">$</span><span class="bn">1</span><span class="op">,</span> r0</span>
|
||
<span id="cb11-7"><a href="#cb11-7" aria-hidden="true" tabindex="-1"></a> sys <span class="dv">4</span><span class="co">; 0:0; 9</span></span>
|
||
<span id="cb11-8"><a href="#cb11-8" aria-hidden="true" tabindex="-1"></a> <span class="bu">mov</span> <span class="op">$</span><span class="bn">1000</span><span class="op">,</span> r2</span>
|
||
<span id="cb11-9"><a href="#cb11-9" aria-hidden="true" tabindex="-1"></a>1:</span>
|
||
<span id="cb11-10"><a href="#cb11-10" aria-hidden="true" tabindex="-1"></a> sys <span class="dv">55</span></span>
|
||
<span id="cb11-11"><a href="#cb11-11" aria-hidden="true" tabindex="-1"></a> sob r2<span class="op">,</span><span class="bn">1b</span></span>
|
||
<span id="cb11-12"><a href="#cb11-12" aria-hidden="true" tabindex="-1"></a> br pdp</span></code></pre></div>
|
||
<p>This is not the code we originally wrote, but it is the code that we
|
||
ultimately used in the program. The string to be printed is shared by
|
||
the <a href="https://en.wikipedia.org/wiki/VAX">VAX</a> and the <a
|
||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>
|
||
code and is located between the two sections.</p>
|
||
<p>First, the program deals with figuring out the address of the string.
|
||
Then the <a href="https://en.wikipedia.org/wiki/Program_counter">program
|
||
counter</a> is saved in a scratch <a
|
||
href="https://en.wikipedia.org/wiki/Processor_register">register</a>.
|
||
Since the program counter points at the second <a
|
||
href="https://en.wikipedia.org/wiki/Instruction_set_architecture#Instructions">instruction</a>,
|
||
we subtract 2 from the scratch register in the second instruction. Then
|
||
we subtract the length of the string and store the result in the
|
||
location with label 0. This has to do with the calling sequence of <a
|
||
href="https://en.wikipedia.org/wiki/System_call">system calls</a> on the
|
||
<a
|
||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>.
|
||
Following the <code>sys</code> instruction is the system call number (4
|
||
for <code>write()</code>), the address of the buffer (pointed to by
|
||
label 0), and the length of the buffer (9). The <a
|
||
href="https://en.wikipedia.org/wiki/File_descriptor">file descriptor</a>
|
||
is in register <code>r0</code>. The rest of the code implements a delay
|
||
loop. In each iteration, a non-existing system call (55) slows things
|
||
down.</p>
|
||
<p>We assembled this program and extracted the <a
|
||
href="https://en.wikipedia.org/wiki/Machine_code">machine code</a> from
|
||
the resulting <a href="https://en.wikipedia.org/wiki/Object_file">object
|
||
file</a>. We used this code in the <a
|
||
href="https://en.wikipedia.org/wiki/VAX">VAX</a> part. Since neither of
|
||
us were fluent in VAX <a
|
||
href="https://en.wikipedia.org/wiki/Assembly_language">assembly</a>, we
|
||
wrote the VAX code in C and massaged the <a
|
||
href="https://en.wikipedia.org/wiki/Compiler">compiler</a> output. The
|
||
VAX assembly program that we came up with is as follows:</p>
|
||
<div class="sourceCode" id="cb12"><pre
|
||
class="sourceCode asm"><code class="sourceCode fasm"><span id="cb12-1"><a href="#cb12-1" aria-hidden="true" tabindex="-1"></a><span class="fu">vax:</span> .<span class="dt">word</span> <span class="dv">0400</span> <span class="op">+</span> <span class="op">(</span>pdp <span class="op">-</span> vax<span class="op">)</span> <span class="op">/</span> <span class="dv">2</span> <span class="op">-</span> <span class="dv">1</span></span>
|
||
<span id="cb12-2"><a href="#cb12-2" aria-hidden="true" tabindex="-1"></a>1:</span>
|
||
<span id="cb12-3"><a href="#cb12-3" aria-hidden="true" tabindex="-1"></a> pushl <span class="op">$</span><span class="bn">9</span></span>
|
||
<span id="cb12-4"><a href="#cb12-4" aria-hidden="true" tabindex="-1"></a> pushal str</span>
|
||
<span id="cb12-5"><a href="#cb12-5" aria-hidden="true" tabindex="-1"></a> pushl <span class="op">$</span><span class="bn">1</span></span>
|
||
<span id="cb12-6"><a href="#cb12-6" aria-hidden="true" tabindex="-1"></a> calls <span class="op">$</span><span class="bn">3</span><span class="op">,</span> write</span>
|
||
<span id="cb12-7"><a href="#cb12-7" aria-hidden="true" tabindex="-1"></a> cvtwl <span class="op">$</span><span class="bn">32767</span><span class="op">,</span> r2</span>
|
||
<span id="cb12-8"><a href="#cb12-8" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb12-9"><a href="#cb12-9" aria-hidden="true" tabindex="-1"></a>2:</span>
|
||
<span id="cb12-10"><a href="#cb12-10" aria-hidden="true" tabindex="-1"></a> decl r2</span>
|
||
<span id="cb12-11"><a href="#cb12-11" aria-hidden="true" tabindex="-1"></a> jneq <span class="dv">2</span><span class="er">b</span></span>
|
||
<span id="cb12-12"><a href="#cb12-12" aria-hidden="true" tabindex="-1"></a> jbr <span class="bn">1b</span></span>
|
||
<span id="cb12-13"><a href="#cb12-13" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb12-14"><a href="#cb12-14" aria-hidden="true" tabindex="-1"></a><span class="fu">write:</span> .<span class="dt">word</span> <span class="dv">0</span></span>
|
||
<span id="cb12-15"><a href="#cb12-15" aria-hidden="true" tabindex="-1"></a> chmk <span class="op">$</span><span class="bn">4</span></span>
|
||
<span id="cb12-16"><a href="#cb12-16" aria-hidden="true" tabindex="-1"></a> <span class="cf">ret</span></span>
|
||
<span id="cb12-17"><a href="#cb12-17" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb12-18"><a href="#cb12-18" aria-hidden="true" tabindex="-1"></a><span class="fu">str:</span> .ascii <span class="st">" :-)\b\b\b\b"</span></span>
|
||
<span id="cb12-19"><a href="#cb12-19" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb12-20"><a href="#cb12-20" aria-hidden="true" tabindex="-1"></a><span class="fu">pdp:</span> .<span class="dt">word</span> <span class="dv">4548</span><span class="op">,</span> <span class="dv">3044</span><span class="op">,</span> <span class="dv">58820</span><span class="op">,</span> <span class="dv">9</span><span class="op">,</span> <span class="dv">4407</span><span class="op">,</span> <span class="dv">6</span><span class="op">,</span> <span class="dv">5568</span><span class="op">,</span> <span class="dv">1</span><span class="op">,</span> <span class="dv">35076</span><span class="op">,</span> <span class="dv">0</span><span class="op">,</span> <span class="dv">9</span><span class="op">,</span> <span class="dv">5570</span><span class="op">,</span> <span class="dv">512</span><span class="op">,</span> <span class="dv">35117</span><span class="op">,</span> <span class="dv">32386</span><span class="op">,</span> <span class="dv">496</span></span></code></pre></div>
|
||
<p>The first word (after the label <code>vax</code>) is the <a
|
||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>
|
||
<a href="https://en.wikipedia.org/wiki/Branch_(computer_science)">branch
|
||
instruction</a>. <a
|
||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>
|
||
branch instructions are octal <code>400+</code> the distance divided by
|
||
2. The string that both the <a
|
||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>
|
||
and <a href="https://en.wikipedia.org/wiki/VAX">VAX</a> programs use is
|
||
after the <code>str</code> label, and the <a
|
||
href="https://en.wikipedia.org/wiki/Programmed_Data_Processor">PDP</a>
|
||
code is after the pdp label.</p>
|
||
<p>On the <a href="https://en.wikipedia.org/wiki/VAX">VAX</a>, the
|
||
program <a
|
||
href="https://en.wikipedia.org/wiki/Stack_(abstract_data_type)">pushes</a>
|
||
9 (the length of the string), the address of the string and 1 (the <a
|
||
href="https://en.wikipedia.org/wiki/File_descriptor">file descriptor</a>
|
||
on the <a
|
||
href="https://en.wikipedia.org/wiki/Stack_(abstract_data_type)">stack</a>
|
||
and calls <code>write(2)</code>. Since we didn’t know the exact calling
|
||
sequence for <a href="https://en.wikipedia.org/wiki/System_call">system
|
||
calls</a>, we just copied the source for the <code>write(2)</code>
|
||
system call stub into our program. After <code>write(2)</code> finishes,
|
||
the program executes a delay loop, after which it jumps back to the
|
||
start of the program.</p>
|
||
<p>We assembled this program, and extracted the <a
|
||
href="https://en.wikipedia.org/wiki/Machine_code">machine code</a> from
|
||
the <a href="https://en.wikipedia.org/wiki/Object_file">object file</a>.
|
||
After this we only had to convert the machine code to <a
|
||
href="https://en.wikipedia.org/wiki/ASCII">ASCII</a> and write a little
|
||
bit of C to glue everything together. We wanted to use different formats
|
||
for each constant in the resulting array, and we wanted to choose the
|
||
format randomly. So we wrote a program to choose an appropriate format
|
||
at random. The program we wrote for that follows. This program actually
|
||
also extracted the machine code from the object file.</p>
|
||
<blockquote>
|
||
<p>NOTE from judges: see <a href="gentab.c">gentab.c</a> for a copy of
|
||
this file that can be compiled in modern systems.</p>
|
||
</blockquote>
|
||
<div class="sourceCode" id="cb13"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb13-1"><a href="#cb13-1" aria-hidden="true" tabindex="-1"></a>\#include <span class="op"><</span>stdio<span class="op">.</span>h<span class="op">></span></span>
|
||
<span id="cb13-2"><a href="#cb13-2" aria-hidden="true" tabindex="-1"></a>\#include <span class="op"><</span>a<span class="op">.</span>out<span class="op">.</span>h<span class="op">></span></span>
|
||
<span id="cb13-3"><a href="#cb13-3" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb13-4"><a href="#cb13-4" aria-hidden="true" tabindex="-1"></a>main<span class="op">(</span>argc<span class="op">,</span> argv<span class="op">)</span> <span class="dt">char</span> <span class="op">**</span>argv<span class="op">;</span></span>
|
||
<span id="cb13-5"><a href="#cb13-5" aria-hidden="true" tabindex="-1"></a><span class="op">{</span></span>
|
||
<span id="cb13-6"><a href="#cb13-6" aria-hidden="true" tabindex="-1"></a> <span class="dt">register</span> <span class="dt">FILE</span> <span class="op">*</span>fp<span class="op">;</span></span>
|
||
<span id="cb13-7"><a href="#cb13-7" aria-hidden="true" tabindex="-1"></a> <span class="dt">register</span> <span class="dt">short</span> pos <span class="op">=</span> <span class="dv">0</span><span class="op">,</span> c<span class="op">,</span> n<span class="op">;</span></span>
|
||
<span id="cb13-8"><a href="#cb13-8" aria-hidden="true" tabindex="-1"></a> <span class="dt">register</span> <span class="dt">char</span> <span class="op">*</span>fmt<span class="op">;</span></span>
|
||
<span id="cb13-9"><a href="#cb13-9" aria-hidden="true" tabindex="-1"></a> <span class="cf">if</span> <span class="op">(</span>argc <span class="op">!=</span> <span class="dv">2</span><span class="op">)</span> <span class="op">{</span></span>
|
||
<span id="cb13-10"><a href="#cb13-10" aria-hidden="true" tabindex="-1"></a> fprintf <span class="op">(</span>stderr<span class="op">,</span> <span class="st">"Usage: </span><span class="sc">%s</span><span class="st"> file</span><span class="sc">\n</span><span class="st">"</span><span class="op">,</span> argv<span class="op">[</span><span class="dv">0</span><span class="op">]);</span></span>
|
||
<span id="cb13-11"><a href="#cb13-11" aria-hidden="true" tabindex="-1"></a> exit <span class="op">(</span><span class="dv">1</span><span class="op">);</span></span>
|
||
<span id="cb13-12"><a href="#cb13-12" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span>
|
||
<span id="cb13-13"><a href="#cb13-13" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb13-14"><a href="#cb13-14" aria-hidden="true" tabindex="-1"></a> <span class="cf">if</span> <span class="op">((</span>fp <span class="op">=</span> fopen<span class="op">(</span>argv<span class="op">[</span><span class="dv">1</span><span class="op">],</span> <span class="st">"r"</span><span class="op">))</span> <span class="op">==</span> NULL<span class="op">)</span> <span class="op">{</span></span>
|
||
<span id="cb13-15"><a href="#cb13-15" aria-hidden="true" tabindex="-1"></a> fprintf<span class="op">(</span>stderr<span class="op">,</span> <span class="st">"</span><span class="sc">%s</span><span class="st">: can't open </span><span class="sc">%s\n</span><span class="st">"</span><span class="op">,</span> argv<span class="op">[</span><span class="dv">0</span><span class="op">],</span> argv<span class="op">[</span><span class="dv">1</span><span class="op">]);</span></span>
|
||
<span id="cb13-16"><a href="#cb13-16" aria-hidden="true" tabindex="-1"></a> exit<span class="op">(</span><span class="dv">2</span><span class="op">);</span></span>
|
||
<span id="cb13-17"><a href="#cb13-17" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span>
|
||
<span id="cb13-18"><a href="#cb13-18" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb13-19"><a href="#cb13-19" aria-hidden="true" tabindex="-1"></a> fseek <span class="op">(</span>fp<span class="op">,</span> <span class="op">(</span><span class="dt">long</span><span class="op">)</span> <span class="kw">sizeof</span> <span class="op">(</span><span class="kw">struct</span> exec<span class="op">),</span> <span class="dv">0</span><span class="op">);</span></span>
|
||
<span id="cb13-20"><a href="#cb13-20" aria-hidden="true" tabindex="-1"></a> printf<span class="op">(</span><span class="st">"/* portable between VAX and PDP11 */</span><span class="sc">\n\n</span><span class="st">"</span><span class="op">);</span></span>
|
||
<span id="cb13-21"><a href="#cb13-21" aria-hidden="true" tabindex="-1"></a> printf <span class="op">(</span><span class="st">"short main[] = {</span><span class="sc">\n</span><span class="st">"</span><span class="op">);</span></span>
|
||
<span id="cb13-22"><a href="#cb13-22" aria-hidden="true" tabindex="-1"></a> <span class="cf">for</span> <span class="op">(;;)</span> <span class="op">{</span></span>
|
||
<span id="cb13-23"><a href="#cb13-23" aria-hidden="true" tabindex="-1"></a> <span class="cf">if</span> <span class="op">(</span>pos <span class="op">==</span> <span class="dv">0</span><span class="op">)</span></span>
|
||
<span id="cb13-24"><a href="#cb13-24" aria-hidden="true" tabindex="-1"></a> printf<span class="op">(</span><span class="st">"</span><span class="sc">\t</span><span class="st">"</span><span class="op">);</span></span>
|
||
<span id="cb13-25"><a href="#cb13-25" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb13-26"><a href="#cb13-26" aria-hidden="true" tabindex="-1"></a> c<span class="op">=</span>getc<span class="op">(</span>fp<span class="op">)</span> <span class="op">&</span> <span class="bn">0377</span><span class="op">;</span></span>
|
||
<span id="cb13-27"><a href="#cb13-27" aria-hidden="true" tabindex="-1"></a> <span class="cf">if</span> <span class="op">(</span>feof<span class="op">(</span>fp<span class="op">))</span> <span class="cf">break</span><span class="op">;</span></span>
|
||
<span id="cb13-28"><a href="#cb13-28" aria-hidden="true" tabindex="-1"></a> n <span class="op">=</span> getc<span class="op">(</span>fp<span class="op">)</span> <span class="op"><<</span> <span class="dv">8</span><span class="op">|</span>c<span class="op">;</span></span>
|
||
<span id="cb13-29"><a href="#cb13-29" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb13-30"><a href="#cb13-30" aria-hidden="true" tabindex="-1"></a> <span class="cf">switch</span> <span class="op">(</span>rand<span class="op">()</span> <span class="op">%</span> <span class="dv">5</span><span class="op">)</span> <span class="op">{</span></span>
|
||
<span id="cb13-31"><a href="#cb13-31" aria-hidden="true" tabindex="-1"></a> <span class="cf">case</span> <span class="dv">0</span><span class="op">:</span></span>
|
||
<span id="cb13-32"><a href="#cb13-32" aria-hidden="true" tabindex="-1"></a> <span class="cf">case</span> <span class="dv">1</span><span class="op">:</span></span>
|
||
<span id="cb13-33"><a href="#cb13-33" aria-hidden="true" tabindex="-1"></a> fmt <span class="op">=</span> <span class="st">"</span><span class="sc">%d</span><span class="st">"</span><span class="op">;</span> <span class="cf">break</span><span class="op">;</span></span>
|
||
<span id="cb13-34"><a href="#cb13-34" aria-hidden="true" tabindex="-1"></a> <span class="cf">case</span> <span class="dv">2</span><span class="op">:</span></span>
|
||
<span id="cb13-35"><a href="#cb13-35" aria-hidden="true" tabindex="-1"></a> fmt <span class="op">=</span> <span class="st">"</span><span class="sc">%u</span><span class="st">"</span><span class="op">;</span> <span class="cf">break</span><span class="op">;</span></span>
|
||
<span id="cb13-36"><a href="#cb13-36" aria-hidden="true" tabindex="-1"></a> <span class="cf">case</span> <span class="dv">3</span><span class="op">:</span></span>
|
||
<span id="cb13-37"><a href="#cb13-37" aria-hidden="true" tabindex="-1"></a> fmt <span class="op">=</span> <span class="st">"0</span><span class="sc">%o</span><span class="st">"</span><span class="op">;</span> <span class="cf">break</span><span class="op">;</span></span>
|
||
<span id="cb13-38"><a href="#cb13-38" aria-hidden="true" tabindex="-1"></a> <span class="cf">case</span> <span class="dv">4</span><span class="op">:</span></span>
|
||
<span id="cb13-39"><a href="#cb13-39" aria-hidden="true" tabindex="-1"></a> fmt <span class="op">=</span> <span class="st">"0x</span><span class="sc">%x</span><span class="st">"</span><span class="op">;</span> <span class="cf">break</span><span class="op">;</span></span>
|
||
<span id="cb13-40"><a href="#cb13-40" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span>
|
||
<span id="cb13-41"><a href="#cb13-41" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb13-42"><a href="#cb13-42" aria-hidden="true" tabindex="-1"></a> <span class="cf">if</span> <span class="op">(</span><span class="dv">32</span> <span class="op"><=</span> n <span class="op">&&</span> n <span class="op"><</span> <span class="dv">127</span> <span class="op">&&</span> <span class="op">(</span>rand<span class="op">()</span> <span class="op">%</span> <span class="dv">4</span><span class="op">))</span> fmt <span class="op">=</span> <span class="st">"'</span><span class="sc">%c</span><span class="st">'"</span><span class="op">;</span></span>
|
||
<span id="cb13-43"><a href="#cb13-43" aria-hidden="true" tabindex="-1"></a> printf<span class="op">(</span>n <span class="op"><</span> <span class="dv">8</span> <span class="op">?</span> <span class="st">"</span><span class="sc">%d</span><span class="st">"</span> <span class="op">:</span> fmt<span class="op">,</span> n<span class="op">);</span></span>
|
||
<span id="cb13-44"><a href="#cb13-44" aria-hidden="true" tabindex="-1"></a> printf<span class="op">(</span><span class="st">","</span><span class="op">);</span></span>
|
||
<span id="cb13-45"><a href="#cb13-45" aria-hidden="true" tabindex="-1"></a> <span class="cf">if</span> <span class="op">(</span>pos<span class="op">++</span> <span class="op">==</span> <span class="dv">8</span><span class="op">)</span> <span class="op">{</span></span>
|
||
<span id="cb13-46"><a href="#cb13-46" aria-hidden="true" tabindex="-1"></a> printf<span class="op">(</span><span class="st">"</span><span class="sc">\n</span><span class="st">"</span><span class="op">);</span></span>
|
||
<span id="cb13-47"><a href="#cb13-47" aria-hidden="true" tabindex="-1"></a> pos <span class="op">=</span> <span class="dv">0</span><span class="op">;</span></span>
|
||
<span id="cb13-48"><a href="#cb13-48" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span>
|
||
<span id="cb13-49"><a href="#cb13-49" aria-hidden="true" tabindex="-1"></a> <span class="cf">else</span> printf<span class="op">(</span><span class="st">" "</span><span class="op">);</span></span>
|
||
<span id="cb13-50"><a href="#cb13-50" aria-hidden="true" tabindex="-1"></a></span>
|
||
<span id="cb13-51"><a href="#cb13-51" aria-hidden="true" tabindex="-1"></a> printf<span class="op">(</span><span class="st">"};</span><span class="sc">\n</span><span class="st">"</span><span class="op">);</span></span>
|
||
<span id="cb13-52"><a href="#cb13-52" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span>
|
||
<span id="cb13-53"><a href="#cb13-53" aria-hidden="true" tabindex="-1"></a><span class="op">}</span></span></code></pre></div>
|
||
<p>As can be seen, there is a slight preference for decimal, and also a
|
||
character format is sometimes used, but only if the data is a printable
|
||
ASCII character.</p>
|
||
<p>When we ran this program, we were almost completely satisfied with
|
||
the result. The only problem we had was that the program had chosen an
|
||
<a href="https://en.wikipedia.org/wiki/Octal">octal</a> representation
|
||
for the first word. Since everybody knows what a <a
|
||
href="https://en.wikipedia.org/wiki/PDP-11">PDP-11</a> branch
|
||
instruction looks like (everyone knows that the traditional magic word
|
||
for an executable, <code>0407</code>, is a <a
|
||
href="https://en.wikipedia.org/wiki/PDP-11">PDP-11</a> <a
|
||
href="https://en.wikipedia.org/wiki/Branch_(computer_science)">branch</a>),
|
||
we changed that to decimal. After checking the size of the resulting
|
||
program we saw that it was one byte too long. The limit was 512 bytes,
|
||
and our program was 513 bytes. So we changed the word <code>and</code>
|
||
in the comment to <code>&&</code>.</p>
|
||
<h2 id="copyright-and-cc-by-sa-4.0-license">Copyright and CC BY-SA 4.0
|
||
License:</h2>
|
||
<p>This file is Copyright (c) 2023 by Landon Curt Noll. All Rights
|
||
Reserved. You are free to share and adapt this file under the terms of
|
||
this license:</p>
|
||
<pre><code>Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)</code></pre>
|
||
<p>For more information, see:
|
||
https://creativecommons.org/licenses/by-sa/4.0/</p>
|
||
<!-- START: this line starts content generated by: bin/gen-inventory.sh -->
|
||
|
||
<h1 id="inventory-for-1984mullender"><a name="inventory"></a>Inventory
|
||
for 1984/mullender</h1>
|
||
<h2 id="primary-files">Primary files</h2>
|
||
<ul>
|
||
<li><a href="index.html">index.html</a> - winner home page</li>
|
||
<li><a
|
||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1984/mullender/mullender.c">mullender.c</a>
|
||
- winning source</li>
|
||
<li><a
|
||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1984/mullender/Makefile">Makefile</a>
|
||
- winner Makefile</li>
|
||
<li><a
|
||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1984/mullender/mullender.alt.c">mullender.alt.c</a>
|
||
- alternative source</li>
|
||
<li><a
|
||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1984/mullender/mullender.orig.c">mullender.orig.c</a>
|
||
- original source</li>
|
||
<li><a
|
||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1984/mullender/a.out.h">a.out.h</a>
|
||
- head file for system who lack it</li>
|
||
<li><a
|
||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1984/mullender/gentab.c">gentab.c</a>
|
||
- author tool to create constants</li>
|
||
<li><a href="1984_mullender.tar.bz2">1984_mullender.tar.bz2</a> -
|
||
download winning source</li>
|
||
</ul>
|
||
<h2 id="secondary-files">Secondary files</h2>
|
||
<ul>
|
||
<li><a
|
||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1984/mullender/.gitignore">.gitignore</a>
|
||
- list of files that should not be committed under git</li>
|
||
<li><a href=".path">.path</a> - directory path from top directory</li>
|
||
<li><a
|
||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1984/mullender/.winner.json">.winner.json</a>
|
||
- description of winner in JSON</li>
|
||
<li><a
|
||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1984/mullender/README.md">README.md</a>
|
||
- markdown source for index.html</li>
|
||
</ul>
|
||
|
||
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|
||
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|
||
|
||
<!-- END: this line ends content from: inc/after-content.default.html -->
|
||
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|
||
|
||
</div>
|
||
|
||
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|
||
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|
||
|
||
</div>
|
||
|
||
<!-- END: this line ends content from: inc/end-row.default.html -->
|
||
<!-- START: this line starts content from: inc/footer.default.html -->
|
||
|
||
<div class="footer">
|
||
<hr>
|
||
<h2>Coda</h2>
|
||
<p><a href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F1984%2Fmullender%2Findex.html">Nu HTML check this web page</a></p>
|
||
<p><a href="#top">Jump to top</a> <a href="#content">Jump to Content</a> <a href="#inventory">Jump to Inventory</a></p>
|
||
</div>
|
||
|
||
<!-- END: this line ends content from: inc/footer.default.html -->
|
||
<!-- START: this line starts content from: inc/bottom.default.html -->
|
||
|
||
</body>
|
||
</html>
|
||
|
||
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|