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<title>1996/schweikh3 - Best Utility</title>
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<div class="header">
  <img src="../../png/ioccc.png" alt="IOCCC image by Matt Zucker" width=300 height=110>
  <h1>The International Obfuscated C Code Contest</h1>
  <h2>1996/schweikh3 - Best Utility</h2>
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<div class="topnav">
  <a class="Left" href="../schweikh2/index.html">&larr; schweikh2</a>
  <a class="Left" href="../index.html">&uarr; 1996 &uarr;</a>
  <a class="Left" href="../westley/index.html">westley &rarr;</a>
  <a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/1996/schweikh3/schweikh3.c">C code</a>
  <a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/1996/schweikh3/Makefile">Makefile</a>
  <a class="Right" href="#inventory">Inventory</a>
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<h2 id="author"><a name="author"></a>Author:</h2>
<ul>
<li>Name: <a href="../../authors.html#Jens_Schweikhardt">Jens
Schweikhardt</a><br> Location: <a href="../../location.html#DE">DE</a> -
<em>Federal Republic of Germany</em> (<em>Germany</em>) <br><br></li>
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<h2 id="to-build">To build:</h2>
<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> all</span></code></pre></div>
<h2 id="to-use">To use:</h2>
<p><strong>WARNING: DO NOT RUN this program without reading this text
down to the end!</strong> It may render your system unusable for a
limited amount of time or force you to reboot using the Big Red Button!
This is <strong>NOT</strong> a joke. You have been warned.</p>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./schweikh3</span></span></code></pre></div>
<h2 id="judges-remarks">Judges’ remarks:</h2>
<p>The source fails to compile on compilers that recognize the inline
keyword by default. For gcc, you may need to use <code>-ansi</code>.</p>
<p>See the file <a href="schweikh3.info">schweikh3.info</a> for example
output from various systems.</p>
<p>But still it is a useful utility. To use try:</p>
<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">./schweikh3</span></span></code></pre></div>
<p>and thanks for the virtual memories! :-)</p>
<h2 id="authors-remarks">Author’s remarks:</h2>
<h3 id="why-i-think-my-entry-is-obfuscated">Why I think my entry is
obfuscated</h3>
<p>There are some layout obfuscations that hinder readability, like some
(but not all) one character tokens in column 1. <code>#include</code>s,
<code>#define</code>s and declarations of data and functions appear
intermixed. <code>iso646.h</code> is even included in the middle of an
expression, how disgusting. Besides, requiring <code>iso646.h</code>
will render the program uncompilable on many systems that have not yet
incorporated Amendment One to The Standard. If you, dear reader, suffer
from this disease, just read <code>iso646.h</code>.</p>
<p>There are no
<code>if' statements. They have been replaced by</code>switch () case
1:<code>or</code>switch () case
0:<code>etc. At least one</code>switch<code>has a declaration after the opening brace, booh! Identifiers are named after random programming languages, BASIC (as</code>Basic`),
COBOL, F77, awk etc.</p>
<p>You have to select maximum ANSI C conformance of your compiler. The
source fails to compile under a C++ compiler due to the `new’ identifier
which is a C++ reserved word:</p>
<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">$</span> g++ schweikh3.c</span>
<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a><span class="ex">schweikh3.c:9:</span> parse error before <span class="kw">`</span><span class="ex">new</span><span class="st">&#39;</span></span>
<span id="cb4-3"><a href="#cb4-3" aria-hidden="true" tabindex="-1"></a><span class="st">schweikh3.c:16: parse error before `new&#39;</span></span>
<span id="cb4-4"><a href="#cb4-4" aria-hidden="true" tabindex="-1"></a><span class="ex">schweikh3.c:46:</span> parse error before <span class="kw">`</span>void<span class="st">&#39;</span></span>
<span id="cb4-5"><a href="#cb4-5" aria-hidden="true" tabindex="-1"></a><span class="st">schweikh3.c:65: parse error before `Lisp&#39;</span></span>
<span id="cb4-6"><a href="#cb4-6" aria-hidden="true" tabindex="-1"></a><span class="ex">schweikh3.c:68:</span> parse error before <span class="kw">`;</span><span class="st">&#39;</span></span>
<span id="cb4-7"><a href="#cb4-7" aria-hidden="true" tabindex="-1"></a><span class="st">[...]</span></span>
<span id="cb4-8"><a href="#cb4-8" aria-hidden="true" tabindex="-1"></a><span class="st">schweikh3.c:91: confused by earlier errors, bailing out</span></span></code></pre></div>
<p>The source fails to compile on compilers that recognize the inline
keyword by default, e.g. gcc:</p>
<div class="sourceCode" id="cb5"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a><span class="ex">$</span> gcc schweikh3.c</span>
<span id="cb5-2"><a href="#cb5-2" aria-hidden="true" tabindex="-1"></a><span class="ex">schweikh3.c:46:</span> parse error before <span class="kw">`</span><span class="ex">void</span><span class="st">&#39;</span></span>
<span id="cb5-3"><a href="#cb5-3" aria-hidden="true" tabindex="-1"></a><span class="st">schweikh3.c: In function `main&#39;</span><span class="ex">:</span></span>
<span id="cb5-4"><a href="#cb5-4" aria-hidden="true" tabindex="-1"></a><span class="ex">schweikh3.c:91:</span> parse error before <span class="kw">`</span>inline<span class="st">&#39;</span></span>
<span id="cb5-5"><a href="#cb5-5" aria-hidden="true" tabindex="-1"></a><span class="st">schweikh3.c: At top level:</span></span>
<span id="cb5-6"><a href="#cb5-6" aria-hidden="true" tabindex="-1"></a><span class="st">schweikh3.c:97: parse error before `void&#39;</span></span></code></pre></div>
<p>The <code>-ansi</code> option to gcc fixes this.</p>
<p>The source fails to compile on obsolete systems with obsolete memory
models due to the identifier <code>far</code> (to be honest: this is
untested :-) ).</p>
<p>Does your indent cope with backslash/newline pairs in between
keywords like in <code>re\turn</code> where the <code>re\</code> is at
the end of a line? ? Solaris’ indent inserts spaces and thereby renders
the source uncompilable…</p>
<p>The indented source will exhibit different semantics when indenting
changes the number of lines (due to using the <code>__LINE__</code>
macro in an expression).</p>
<p>And what about <code>sizeof __TIME__</code>? This one’s for the
philosophers and physicists among us programmers. What is it?
<code>sizeof (char *)</code>? – no. <code>strlen ("hh:mm:ss")</code>? –
no. It’s the same as <code>sizeof __DATE__ - sizeof "no"</code> :-)</p>
<p>The program is POSIX conformant and lints without warning under
Solaris’ Sunpro lint. Allocated memory is correctly freed on all
possible execution paths.</p>
<h3 id="what-this-program-does">What this program does</h3>
<p>This program tests your operating system’s allocation honesty. It
forks a child that will allocate as much memory as possible with byte
granularity and then write to every 1024th byte, at the same time
writing a status report on <code>stdout</code>. This way each page of
the allocated virtual memory will eventually be referenced. Without any
arguments, <code>malloc(3)</code> will be used to allocate memory. If
the first arg starts with <code>c</code>, <code>calloc(3)</code> will be
used instead.</p>
<p>I distinguish three different behaviours:</p>
<ol type="1">
<li><p>OS without memory overcommit: <code>malloc(3)</code> does not lie
– you can use all memory the OS granted to you.</p></li>
<li><p>OS with memory overcommit: <code>malloc(3)</code> lies – any
program may get killed at random when the OS can not acquire a free
page.</p></li>
<li><p>OS with pseudo memory overcommit: <code>malloc(3)</code> lies –
The OS puts processes to sleep for which it can not acquire a free page.
Because other processes are also affected this way, the system slows
down and quickly becomes totally unusable (also known as “thrashing”).
Because more and more processes wait for memory returned by other
exiting processes the system eventually enters a deadlock situation and
effectively halts.</p></li>
</ol>
<p>I had the pleasure and pain to find all three behaviours on the
platforms I use regularly.</p>
<p>The file <a href="schweikh3.info">schweikh3.info</a> has output for
Solaris, FreeBSD and Linux. The Linux case is interesting in that the
behaviour changes when <code>calloc(3)</code> is used instead of
<code>malloc(3)</code>. For FreeBSD, the last two lines are not messages
stemming from my program but issued by the syslog daemon.</p>
<h3 id="implementation-remarks">Implementation remarks</h3>
<p>How can we distinguish the three different OS types from the table
above?</p>
<p>Obviously, type (1), no overcommit, is easy.</p>
<p>For type (2), random kill, we need to fork a child that can be killed
and whose exit status the parent collects and decodes. Here’s where
POSIX enters the scene.</p>
<p>Type (3), thrashing, was the hardest part. The first attempt was to
measure the elapsed processor time it takes to write a single byte
(using <code>clock()</code>). If a certain threshold is reached I assume
the system is thrashing. When thrashing, however, the process does not
consume processor time in a noticeable amount any longer and I lose. So
I switched to measuring wall clock time using <code>time(3)</code>. On
the one system that I observe thrashing (Linux) this works (although the
value returned by <code>time(3)</code> seems to ‘hang’ sometimes when
the OS thrashes. Exceeding a threshold of 5 seconds may be detected only
after half a minute or so.</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>

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<h1 id="inventory-for-1996schweikh3"><a name="inventory"></a>Inventory
for 1996/schweikh3</h1>
<p><a href="#top">Jump to top</a></p>
<h2 id="primary-files">Primary files</h2>
<ul>
<li><a
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1996/schweikh3/schweikh3.c">schweikh3.c</a>
- entry source</li>
<li><a
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1996/schweikh3/Makefile">Makefile</a>
- entry Makefile</li>
<li><a
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1996/schweikh3/schweikh3.orig.c">schweikh3.orig.c</a>
- original source</li>
<li><a
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1996/schweikh3/schweikh3.info">schweikh3.info</a>
- example output from various systems</li>
<li><a href="1996_schweikh3.tar.bz2">1996_schweikh3.tar.bz2</a> -
download entry source</li>
</ul>
<h2 id="secondary-files">Secondary files</h2>
<ul>
<li><a href="index.html">index.html</a> - entry home page</li>
<li><a
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1996/schweikh3/.entry.json">.entry.json</a>
- description of entry in JSON</li>
<li><a
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1996/schweikh3/.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/1996/schweikh3/README.md">README.md</a>
- markdown source for index.html</li>
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