We add the following level-3 header to help people identify text they may wish to skip if they wish for a greater challenge: ``` ``` After that notice we add: ``` **If you want a greater challenge, don't read any further**: just try to understand the program via the source. If you get stuck, come back and read below for additional hints and information. ``` And sometimes follow with: ``` ``` Or sometimes follow with: ``` ``` Where the alt code impacts a "greater challenge", we add instead: ``` **If you want a greater challenge, don't read any further**: just try to understand the program without looking at the Alternate code. If you get stuck, come back and look at the Alternate code. ``` And where a given command impacts a "greater challenge", we add instead: ``` **If you want a greater challenge, don't read any further**: just try to understand the program without running the command below. If you get stuck, come back and run the following command: ``` Perform `make www` to perform the above and test under macOS.
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<h1>The International Obfuscated C Code Contest</h1>
|
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<h2>2015/burton - Most useful</h2>
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<a class="Left Disabled" href="#">first entry</a>
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<a class="Left" href="../index.html">↑ 2015 ↑</a>
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<a class="Left" href="../dogon/index.html">dogon →</a>
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<a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/prog.c">C code</a>
|
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<a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/Makefile">Makefile</a>
|
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<a class="Right" href="#inventory">Inventory</a>
|
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<a class="Right" href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F2015%2Fburton%2Findex.html">✓</a>
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<h2 id="author">Author:</h2>
|
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<ul>
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<li>Name: <a href="../../authors.html#Dave_Burton">Dave Burton</a><br>
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Location: <a href="../../location.html#US">US</a> - <em>United States of America</em> (<em>United States</em>)</li>
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<!-- BEFORE: 1st line of markdown file: 2015/burton/README.md -->
|
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<h2 id="to-build">To build:</h2>
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||
<pre><code> make</code></pre>
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<h2 id="to-use">To use:</h2>
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<pre><code> ./prog "expression"</code></pre>
|
||
<p>or:</p>
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||
<pre><code> ./prog</code></pre>
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<p>Type in expressions on standard input.</p>
|
||
<h2 id="try">Try:</h2>
|
||
<pre><code> ./try.sh</code></pre>
|
||
<p>Notice how the script reads in from a file. If you type just:</p>
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||
<pre><code> ./prog</code></pre>
|
||
<p>it will prompt you in the same way. Send ctrl-c to exit.</p>
|
||
<p>Finally, if you wish to read the man page:</p>
|
||
<pre><code> man ./calc.1</code></pre>
|
||
<h2 id="alternate-code">Alternate code:</h2>
|
||
<p>An alternate version of this entry, <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/prog.alt.c">prog.alt.c</a>, is provided.
|
||
This alternate code is discussed in the “prog.c vs prog.alt.c” section of the
|
||
author’s remarks below.</p>
|
||
<h3 id="alternate-build">Alternate build:</h3>
|
||
<pre><code> make alt</code></pre>
|
||
<h3 id="alternate-use">Alternate use:</h3>
|
||
<p>Use <code>prog.alt</code> as you would <code>prog</code> above.</p>
|
||
<h2 id="judges-remarks">Judges’ remarks:</h2>
|
||
<p>“Look, Ma, no <del>hands</del> digits!”</p>
|
||
<p>The place where some arithmetic operations are done, for example, division or
|
||
modulo, are easy to find. Where are addition and subtraction?</p>
|
||
<p>We were impressed with the level of detail the author “blogged” the obfuscation
|
||
process.</p>
|
||
<h2 id="authors-remarks">Author’s remarks:</h2>
|
||
<h3 id="calc---an-integer-expression-calculator-that-outputs-in-both-hex-and-decimal">calc - an integer expression calculator that outputs in both hex and decimal</h3>
|
||
<p>All useful tools should include sufficient documentation.
|
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See the included man page. ;-)</p>
|
||
<h3 id="notes">Notes</h3>
|
||
<p>This program is named <code>calc</code>. Onomatopoeia of sorts, in the visual realm. The
|
||
formatting was easier: Form Follows Function (although <a href="../../2011/hou/hint.html" title="Hou Qiming">Hou</a> did this
|
||
better). It was tempting to call it iCalc, with <code>i</code> for integer (and it was
|
||
written on an <code>iDevice</code>), but sanity prevailed.</p>
|
||
<p>Printed in 8 pt Courier, it makes aesthetically pleasing 8.5 x 11 wall art.</p>
|
||
<h3 id="prog.c-vs-prog.alt.c">prog.c vs prog.alt.c</h3>
|
||
<p><a href="../../authors.html#Dominik_Muth">Dominik Muth</a> observed a syntax error on <code>1+1</code>,
|
||
<code>1-1</code>, <code>1|1</code>, and <code>1^1</code> when using an ARM based computer, although <code>1*1</code> and
|
||
others worked correctly. This occurs because some platforms by default treat
|
||
<code>char</code> as <code>unsigned char</code>. The original code has this weakness, which can be
|
||
corrected by adding <code>-fsigned-char</code> to the compile line.</p>
|
||
<p>The modified code is agnostic to <code>char</code> signedness.</p>
|
||
<h3 id="why-is-this-entry-obfuscatedinteresting">Why is this entry obfuscated/interesting?</h3>
|
||
<p>Yes, this is another calculator program.</p>
|
||
<p>However, unlike any other calculator source code the author is aware of,
|
||
this one contains no digits. At all. Anywhere. As in</p>
|
||
<pre><code> grep '[0-9]' prog.c || echo no digits!</code></pre>
|
||
<p>Nor are the digits simply obfuscated. There are no character constants. There
|
||
is only one single, short string, and it does not contain any obfuscated digits.
|
||
And yet the output is in decimal and hexadecimal, and it accepts octal, decimal,
|
||
and hex input.</p>
|
||
<p>Flow control is by <code>for</code> and <code>return</code>. It is <code>if</code>-less, <code>switch</code>-less,
|
||
<code>while</code>-less, and hopeless. Literally, if not figuratively. ;-)</p>
|
||
<p>The code size is intentionally 2015, as stated by <code>iocccsize -i</code>, and can be
|
||
reformatted without changes (as in <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/rule2.c">rule2.c</a> source) to exactly 4096 octets.</p>
|
||
<p>Finally, <code>calc</code> is interesting, if for no other reason than it is practically
|
||
useful: Hex/decimal conversion, arithmetic, byte-swapping, bit-shifting, and
|
||
logical operations with memory, on the command line, or interactively.</p>
|
||
<h3 id="but-the-question-is-why-is-the-entry-obfuscated">But the question is why is the entry obfuscated?</h3>
|
||
<p>The code follows many industry best-practices:</p>
|
||
<ul>
|
||
<li><p>You know what it does just by looking at it.</p></li>
|
||
<li><p>Numbers and digits have often been used for obfuscation,
|
||
so in a bid for better clarity, this code has no digits at all.</p></li>
|
||
<li><p>In the spirit of clarity, most of the variables are declared before use, so
|
||
they are readily visible, with single letter names that don’t clutter the
|
||
screen, in a tautological arrangement.</p></li>
|
||
<li><p>More helpful is the use of <code>typedef</code>s instead of <code>#define</code>, so the types
|
||
remain useful even in the debugger, and source code beautifiers will not undo
|
||
careful presentation.</p></li>
|
||
<li><p><code>#defines</code> are used here in the best spirit of the preprocessor: to shorten
|
||
repetitive constructs, not for obscurity.</p></li>
|
||
<li><p>All functions are short (and therefore easy to understand?) and do only one
|
||
thing, well, ….</p></li>
|
||
<li><p>Curly braces invite endless holy wars over readability. This code only uses
|
||
them for function definitions, thereby greatly improving readability, and
|
||
reducing arguments about said readability.</p></li>
|
||
<li><p>One of C’s many blessings (until recently) is a modicum of keywords, of which
|
||
only 8 are used: <code>for</code>, <code>return</code>, <code>typedef</code>, <code>void</code>, <code>char</code>, <code>short</code>, <code>unsigned</code>
|
||
and <code>long</code>; 10 if <code>#include</code> and <code>#define</code> are counted.</p></li>
|
||
<li><p>The code helpfully declares <code>"syntax_error!"</code> right up front, filling the
|
||
reader with confidence.</p></li>
|
||
<li><p>In spite of its inherent clarity, the code was presented to both <code>indent(1)</code>
|
||
and <code>clang-format(1)</code>, after running it through the preprocessor, sustaining its
|
||
better qualities.</p></li>
|
||
<li><p>That the code is obfuscated is spelled out two different ways in the source;
|
||
it helps to reformat the code to see the second spelling.</p></li>
|
||
<li><p>The author is overly fond of the code that handles input. There is no memory
|
||
allocation, nor pre-allocation of arrays, so where does the memory come from?
|
||
The multi-base <code>strtol(3)</code> code is pretty tricky. No special attempt was made to
|
||
replace operations with obscure mathematical relations, as the (lack of) beauty
|
||
is in the parsing – ask not where is the modulus operation, but how does it
|
||
know when to mod – okay, but where is add and subtract? And really, who
|
||
doesn’t enjoy a <code>setjmp(3)</code> in the argument list?</p></li>
|
||
<li><p>Finally, documentation of the source code structure is helpfully provided in
|
||
rot13 format. But isn’t it unsportsmanlike to rely upon it? However, even with
|
||
this helpful guide, things like reading input lines remain as tricky to read as
|
||
they are to write.</p></li>
|
||
</ul>
|
||
<h3 id="compiler-warnings">Compiler warnings</h3>
|
||
<p><code>calc</code> is C99 compliant, and is ANSI/C90 compliant except for wanting 64-bit <code>long long</code>. Changing the two <code>long long</code> typedefs to <code>long</code>, and compiling with <code>gcc -m32</code> yields a program that operates on 32-bit values, with wrap-around of
|
||
shifts mod 32:</p>
|
||
<pre><code> 1<<48
|
||
65536 0x00010000</code></pre>
|
||
<p>gcc 4.2.1 without arguments compiles cleanly (e.g. <code>cc prog.c -o prog</code>).
|
||
This is my workaday compiler. gcc is also clean with <code>-ansi</code>, and <code>-std=c99</code>.</p>
|
||
<p>clang 3.6.0 lives up to its namesake, resounding on non-problems.
|
||
To stifle these complaints:</p>
|
||
<pre><code> -Wno-return-type -Wno-parentheses -Wno-empty-body</code></pre>
|
||
<p>When invoked with <code>-ansi -pedantic</code>, there are two warnings, which can be ignored:</p>
|
||
<ul>
|
||
<li><code>ISO C90 does not support 'long long'</code></li>
|
||
</ul>
|
||
<p>With <code>-Wall -std=c99</code>, both are quite noisy, and all can be ignored:</p>
|
||
<ul>
|
||
<li><code>array subscript has type 'char' [-Wchar-subscripts]</code></li>
|
||
<li><code>value computed is not used [-Wunused-value]</code></li>
|
||
<li><code>operation on 'j' may be undefined [-Wsequence-point]</code></li>
|
||
</ul>
|
||
<h3 id="test-suite">Test Suite:</h3>
|
||
<p>If the program name begins with an <code>e</code>, it echoes <code>stdin</code> to <code>stdout</code>.
|
||
This allows for a convenient test suite:</p>
|
||
<pre><code> ln -sf prog eprog
|
||
PATH=. eprog < test.in | diff - test.out</code></pre>
|
||
<h3 id="notice-to-those-who-wish-for-a-greater-challenge">NOTICE to those who wish for a greater challenge</h3>
|
||
<p><strong>If you want a greater challenge, don’t read any further</strong>:
|
||
just try to understand the program via the source.</p>
|
||
<p>If you get stuck, come back and read below for additional hints and information.</p>
|
||
<h3 id="obfuscation">Obfuscation:</h3>
|
||
<p>If you do not want to puzzle out how it works, see <a href="obfuscation.html">obfuscation.html</a>.</p>
|
||
<!--
|
||
|
||
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
||
|
||
You are free to share and adapt this file under the terms of this license:
|
||
|
||
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
|
||
|
||
For more information, see:
|
||
|
||
https://creativecommons.org/licenses/by-sa/4.0/
|
||
|
||
-->
|
||
<!-- AFTER: last line of markdown file: 2015/burton/README.md -->
|
||
|
||
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|
||
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|
||
|
||
<!-- START: this line starts content generated by: bin/output-index-inventory.sh -->
|
||
|
||
<div id="inventory">
|
||
<h1 id="inventory-for-2015burton">Inventory for 2015/burton</h1>
|
||
</div>
|
||
<h2 id="primary-files">Primary files</h2>
|
||
<ul>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/prog.c">prog.c</a> - entry source code</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/Makefile">Makefile</a> - entry Makefile</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/prog.alt.c">prog.alt.c</a> - alternate source code</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/prog.orig.c">prog.orig.c</a> - original source code</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/try.sh">try.sh</a> - script to try entry</li>
|
||
<li><a href="try.this.txt">try.this.txt</a> - input file used by try.sh</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/calc.1">calc.1</a> - man page for integer expression calculator</li>
|
||
<li><a href="road.to.obscurity.html">road.to.obscurity.html</a> - obfuscated calculator development notes</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/rule2.c">rule2.c</a> - iocccsize.c reformatted to exactly 4096 octets</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/test32.out">test32.out</a> - test suite comparison data for 32-bit systems</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/test.in">test.in</a> - test suite input data</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/test.out">test.out</a> - test suite comparison data</li>
|
||
<li><a href="obfuscation.html">obfuscation.html</a> - obfuscation information web page</li>
|
||
<li><a href="src.doc.txt">src.doc.txt</a> - hints about the source code</li>
|
||
</ul>
|
||
<h2 id="secondary-files">Secondary files</h2>
|
||
<ul>
|
||
<li><a href="2015_burton.tar.bz2">2015_burton.tar.bz2</a> - download entry tarball</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/README.md">README.md</a> - markdown source for this web page</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/.entry.json">.entry.json</a> - entry summary and manifest in JSON</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/.gitignore">.gitignore</a> - list of files that should not be committed under git</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/obfuscation.md">obfuscation.md</a> - markdown source for obfuscation.html</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/.path">.path</a> - directory path from top level directory</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/burton/road.to.obscurity.md">road.to.obscurity.md</a> - markdown source for road.to.obscurity.html</li>
|
||
<li><a href="index.html">index.html</a> - this web page</li>
|
||
</ul>
|
||
<hr style="width:10%;text-align:left;margin-left:0">
|
||
<h4>
|
||
Jump to: <a href="#">top</a>
|
||
</h4>
|
||
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|
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</div>
|
||
|
||
<!-- END: this line ends content from: inc/after-content.default.html -->
|
||
<!-- START: this line starts content from: inc/footer.inventory.html -->
|
||
|
||
<!--
|
||
|
||
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
||
|
||
You are free to share and adapt this file under the terms of this license:
|
||
|
||
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
|
||
|
||
For more information, see:
|
||
|
||
https://creativecommons.org/licenses/by-sa/4.0/
|
||
|
||
-->
|
||
|
||
<div class="footer">
|
||
|
||
<div id="copyright"><h3>Copyright © 1984-2024 by Landon Curt Noll:
|
||
<a href="https://creativecommons.org/faq/#what-does-some-rights-reserved-mean"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">Some Rights Reserved</a></h3>
|
||
<p>
|
||
This work is <b>licensed by Landon Curt Noll</b> under
|
||
<b><a href="https://creativecommons.org/licenses/by-sa/4.0/?ref=chooser-v1"
|
||
target="_blank"
|
||
rel="license noopener noreferrer"
|
||
style="display:inline-block;">CC BY-SA 4.0</a></b>.
|
||
<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
||
src="../../png/cc.png"
|
||
alt="cc inside circle symbol">
|
||
<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
||
src="../../png/by.png"
|
||
alt="person inside circle symbol">
|
||
<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
||
src="../../png/sa.png"
|
||
alt="arrow looping back on itself inside circle symbol"><br>
|
||
You should <b>carefully review</b> the
|
||
<b><a href="https://creativecommons.org/licenses/by-sa/4.0/legalcode.en"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">CC BY-SA 4.0 LEGAL CODE</a></b>
|
||
before using the licensed material.<br>
|
||
You may wish to review the
|
||
<b><a href="../../license.html"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">highlights of some of the key features and terms</a></b>
|
||
of <b>CC BY-SA 4.0</b>.<br>
|
||
</p>
|
||
</div>
|
||
|
||
<div id="coda"><h3>Coda</h3>
|
||
<p>
|
||
<a href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F2015%2Fburton%2Findex.html" rel="nofollow">Nu HTML check this web page</a><br>
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<a href="#top">Jump to top</a> <a href="#content">Jump to Content</a> <a href="#inventory">Jump to Inventory</a><br>
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|
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