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Remove hint.html and index.html

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As per discussions on GitHub the index.html and hint.html files should
be deleted in favour of README.md files (from any
.text/.txt/.markdown/.md files which will be turned into README.md in an
upcoming commit).
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Cody Boone Ferguson committed 2023-02-08 05:07:05 -08:00
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2019/endoh/hint.html
-124
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta name="GENERATOR" content="mkd2html 2.2.0">
<meta http-equiv="Content-Type"
content="text/html; charset=utf-8"> <link rel="stylesheet"
type="text/css"
href="../hint.css">
<title>Most in need of debugging</title>
</head>
<body>
<h1>Most in need of debugging</h1>
<p>Yusuke Endoh<br>
Twitter: @mametter</p>
<h2>Judges' comments:</h2>
<h3>To use:</h3>
<pre><code>make
</code></pre>
<h3>Try:</h3>
<pre><code>./prog
gdb ./prog || llvm ./prog
</code></pre>
<h3>Selected Judges Remarks:</h3>
<p>The purpose of this program is to crash. You&rsquo;ll want to have memorized &ldquo;man
ascii&rdquo; when debugging it to reveal its purpose.</p>
<h2>Author&rsquo;s comments:</h2>
<h3>backtrace quine</h3>
<p>Compile prog.c with no optimization.</p>
<pre><code>$ gcc -g -O0 -o prog prog.c
</code></pre>
<p>Then, run it. You will see a segmentation fault.</p>
<pre><code>$ ./prog
Segmentation fault (core dumped)
</code></pre>
<p>Let&rsquo;s debug. As usual, run it under gdb.</p>
<pre><code>$ gdb ./prog
(gdb) run
Starting program: /home/.../prog
Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
</code></pre>
<p>Okay, check the backtrace.</p>
<pre><code>(gdb) backtrace
#0 0x0000000000000000 in ?? ()
#1 0x0000555555555201 in x23 () at prog.c:35
#2 0x000055555555571a in x64 () at prog.c:100
#3 0x0000555555555747 in x65 () at prog.c:101
#4 0x0000555555555774 in x66 () at prog.c:102
#5 0x00005555555557ce in x69 () at prog.c:105
#6 0x0000555555555828 in x6e () at prog.c:110
#7 0x0000555555555747 in x65 () at prog.c:101
...
</code></pre>
<p>See the line numbers and lookup the ASCII table.</p>
<pre><code> 35 = '#'
100 = 'd'
101 = 'e'
102 = 'f'
105 = 'i'
110 = 'n'
101 = 'e'
...
</code></pre>
<h4>One more thing</h4>
<p>The original program can be used as a GDB command file.</p>
<pre><code>$ gdb -q -x prog.c ./prog | cat
Reading symbols from ./prog...done.
Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
#0 0x0000000000000000 in ?? ()
#1 0x0000555555555201 in x23 () at prog.c:35
#2 0x000055555555571a in x64 () at prog.c:100
#3 0x0000555555555747 in x65 () at prog.c:101
#4 0x0000555555555774 in x66 () at prog.c:102
#5 0x00005555555557ce in x69 () at prog.c:105
#6 0x0000555555555828 in x6e () at prog.c:110
#7 0x0000555555555747 in x65 () at prog.c:101
...
</code></pre>
<p>By using this, you can confirm that it is actually a quine.</p>
<pre><code>$ gdb -q -x prog.c ./prog | sed -n -r 's/#.*:([0-9]+)/\1/p' | awk '{printf "%c",$1}' &gt; prog2.c
$ diff prog.c prog2.c
</code></pre>
<hr />
<TABLE><TR>
<TD><a rel="license" href="https://creativecommons.org/licenses/by-sa/3.0/"><img alt="Creative Commons License" style="border-width:0" src="/png/by-sa-3.0-88x31.png" /></a></TD>
<TD><P>&copy; Copyright 1984-2019,
<A HREF="/judges.html">Leo Broukhis, Simon Cooper, Landon Curt Noll</A>
- All rights reserved<BR>
This work is licensed under a <a rel="license" href="https://creativecommons.org/licenses/by-sa/3.0/">Creative Commons Attribution-ShareAlike 3.0 Unported License</a>.</P></TD>
<TD>&nbsp;<!--<a href="https://validator.w3.org/check?uri=referer"><img src="https://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01 Transitional" height="31" width="88"></a>--></TD>
</TR></TABLE>
</body>
</html>