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force use of pandoc version >= 3.1.12.2

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The `bin/pandoc-wrapper.sh` tool will verify that the ssytem
has a recent enough version of `pandoc(1)`.

We explain why we insist on `pandoc(1)`. version >= 3.1.12.2
in comments where the $PANDOC_MIN_VERSION is set.

Added `--wrap=preserve` as a default argument to `pandoc(1)`.
While this change will impact every HTML file generated,
we believe this will improve the ability of someone to look
at the generated HTML and correlate with the original markdown.

Changed `bin/pandoc-wrapper.sh` VERSION from "1.4.2 2024-03-17"
to "1.4.3 2024-03-18".

Performed `make www` to achieve all of the above and to generate
HTML using the new  `--wrap=preserve` `pandoc(1)` mode.
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Landon Curt Noll committed 2024-03-18 01:26:39 -07:00
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<h1
id="conflicting-compilers-and-optimisers-that-broke-this-entry-in-2023">Conflicting
compilers and optimisers that broke this entry in 2023</h1>
<p>As briefly noted in the <a href="README.md">README.md</a> gcc and
clang caused different problems with this entry depending on the
optimiser being enabled or not, where if the optimiser was enabled it
would work with one compiler and not the other. But if you then disabled
the optimiser the opposite problem would occur: the working compiler
would no longer work and the non-functional one would start to work! And
then there’s the problem of linux versus macOS causing problems.</p>
<p>The <a href="marshall.alt.c">alternate code</a> (source code)
demonstrates the problem so you can see if your compiler has the problem
as described below.</p>
<p>In some versions of gcc and clang (this was first discovered in
fedora linux 38) if the compiler was enabled one compiler would generate
code that segfaulted but the other one would not. However, when then
disabling the optimiser the compiler that had no problem suddenly did
and the one that did suddenly did not. But segfaulting was not by any
means the only problem.</p>
<p>Another problem was that depending on the optimiser an infinite loop
would be entered. But then removing it would cause other problems as
well, including a segfault.</p>
<p>It was not only one compiler that dumped core. Both dumped core with
other behaviour, depending on what changes in code were made and the
optimiser being on or off. Clang in macOS also dumped core!</p>
<p>The <a href="README.md#alternate-code">alternate code</a> (README.md)
has the original fix for clang which works with some compilers depending
on the optimiser. When we refer to the code below we refer to the
alternate code.</p>
<h2 id="the-conflicting-compiler-problems">The conflicting compiler
problems:</h2>
<p>Below we describe the conflicting options that resulted in the need
to modify the original code.</p>
<h1 id="conflicting-compilers-and-optimisers-that-broke-this-entry-in-2023">Conflicting compilers and optimisers that broke this entry in 2023</h1>
<p>As briefly noted in the <a href="README.md">README.md</a> gcc and clang caused different
problems with this entry depending on the optimiser being enabled or not, where
if the optimiser was enabled it would work with one compiler and not the other.
But if you then disabled the optimiser the opposite problem would occur: the
working compiler would no longer work and the non-functional one would start to
work! And then there’s the problem of linux versus macOS causing problems.</p>
<p>The <a href="marshall.alt.c">alternate code</a> (source code) demonstrates the problem so
you can see if your compiler has the problem as described below.</p>
<p>In some versions of gcc and clang (this was first discovered in fedora linux 38)
if the compiler was enabled one compiler would generate code that segfaulted but
the other one would not. However, when then disabling the optimiser the compiler
that had no problem suddenly did and the one that did suddenly did not. But
segfaulting was not by any means the only problem.</p>
<p>Another problem was that depending on the optimiser an infinite loop would be
entered. But then removing it would cause other problems as well, including a
segfault.</p>
<p>It was not only one compiler that dumped core. Both dumped core with other
behaviour, depending on what changes in code were made and the optimiser being
on or off. Clang in macOS also dumped core!</p>
<p>The <a href="README.md#alternate-code">alternate code</a> (README.md) has the original fix
for clang which works with some compilers depending on the optimiser. When we
refer to the code below we refer to the alternate code.</p>
<h2 id="the-conflicting-compiler-problems">The conflicting compiler problems:</h2>
<p>Below we describe the conflicting options that resulted in the need to modify
the original code.</p>
<h3 id="linux">Linux</h3>
<p>With the optimiser disabled GCC compiled the code to enter an
infinite loop. Enabling the optimiser and it worked fine. But if the
optimiser is enabled clang generates code that first prints the text
twice (it should print it once) and then immediately dumps core!</p>
<p>But then there’s that infinite loop. What happens if we remove
it?</p>
<p>Once the loop is removed if we compile with clang and the optimiser
is disabled all is okay. If however we compile with gcc and the
optimiser is disabled the string is printed once and then the program
dumps core! Why is this? It is because of the call to
<code>_exit()</code> (see below).</p>
<p>Clang works fine with the loop removed and the optimiser disabled. If
however we enable the optimiser clang will generate code that prints the
string twice and dumps core just like before! What about the call to
<code>_exit()</code>?</p>
<p>With the optimiser disabled GCC compiled the code to enter an infinite loop.
Enabling the optimiser and it worked fine. But if the optimiser is enabled clang
generates code that first prints the text twice (it should print it once) and
then immediately dumps core!</p>
<p>But then there’s that infinite loop. What happens if we remove it?</p>
<p>Once the loop is removed if we compile with clang and the optimiser is disabled
all is okay. If however we compile with gcc and the optimiser is disabled the
string is printed once and then the program dumps core! Why is this? It is
because of the call to <code>_exit()</code> (see below).</p>
<p>Clang works fine with the loop removed and the optimiser disabled. If however we
enable the optimiser clang will generate code that prints the string twice and
dumps core just like before! What about the call to <code>_exit()</code>?</p>
<p>The call was:</p>
<div class="sourceCode" id="cb1"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a>_exit<span class="op">(</span>argv<span class="op">[(</span><span class="dt">int</span><span class="op">)*</span>argc<span class="op">-</span><span class="dv">2</span><span class="op">/</span>cc<span class="op">[</span><span class="dv">1</span><span class="op">*(</span><span class="dt">int</span><span class="op">)*</span>argc<span class="op">]|-</span><span class="dv">1</span><span class="op">&lt;&lt;</span><span class="dv">4</span><span class="op">]);</span></span></code></pre></div>
<p>Changing it to not refer to these variables and just exit 1 and the
problems disappear!</p>
<p>Changing it to not refer to these variables and just exit 1 and the problems
disappear!</p>
<h3 id="macos">macOS</h3>
<p>But then there was macOS which had another problem!</p>
<p>If the infinite loop is not removed/commented out and the optimiser
is enabled it works fine but if it’s disabled it prints out the string
and then enters an infinite loop!</p>
<p>After we fix the infinite loop if we change the <code>_exit()</code>
call in macOS and disable the optimiser we might get something like:</p>
<p>If the infinite loop is not removed/commented out and the optimiser is enabled
it works fine but if it’s disabled it prints out the string and then enters an
infinite loop!</p>
<p>After we fix the infinite loop if we change the <code>_exit()</code> call in macOS and
disable the optimiser we might get something like:</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">$</span> ./marshall</span>
<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a> <span class="ex">choo</span> choo</span>
<span id="cb2-3"><a href="#cb2-3" aria-hidden="true" tabindex="-1"></a><span class="ex">Segmentation</span> fault: 11</span></code></pre></div>
<p>Observe how it doesn’t print it twice. But of course it segfaults so
it’s not right either.</p>
<p>If the optimiser is enabled, however, we will see that it works fine
before the change to <code>_exit()</code>.</p>
<p>Observe how it doesn’t print it twice. But of course it segfaults so it’s not
right either.</p>
<p>If the optimiser is enabled, however, we will see that it works fine before the
change to <code>_exit()</code>.</p>
<h2 id="summary">Summary</h2>
<p>And that is the tale of a little <strike>engine</strike> train that
could…eventually! Or perhaps it’s the compilers, optimisers and OSes
that eventually could?</p>
<p>Whichever you wish it to be, it now works with both clang and gcc!
Choo choo!</p>
could…eventually! Or perhaps it’s the compilers, optimisers and OSes that
eventually could?</p>
<p>Whichever you wish it to be, it now works with both clang and gcc! Choo choo!</p>
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