NaCl docs: mention static libraries for SJLJ

native_client_sdk/doc_generated/reference/pnacl-c-cpp-language-support.html

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 <section id="pnacl-c-c-language-support">
 <h1 id="pnacl-c-c-language-support">PNaCl C/C++ Language Support</h1>
 <div class="contents local" id="contents" style="display: none">
 <ul class="small-gap">
 <li><p class="first"><a class="reference internal" href="#source-language-support" id="id3">Source language support</a></p>
 <ul class="small-gap">
 <li><a class="reference internal" href="#versions" id="id4">Versions</a></li>
 <li><a class="reference internal" href="#preprocessor-definitions" id="id5">Preprocessor definitions</a></li>
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 <p>PNaCl and NaCl support <code>setjmp</code> and <code>longjmp</code> without any
 restrictions beyond C&#8217;s.</p>
 <h2 id="c-exception-handling"><span id="exception-handling"></span>C++ Exception Handling</h2>
 <p>PNaCl currently supports C++ exception handling through <code>setjmp()</code> and
 <code>longjmp()</code>, which can be enabled with the <code>--pnacl-exceptions=sjlj</code>
 linker flag. Exceptions are disabled by default so that faster and
 smaller code is generated, and <code>throw</code> statements are replaced with
 calls to <code>abort()</code>. The usual <code>-fno-exceptions</code> flag is also
 supported. PNaCl will support full zero-cost exception handling in the
 future.</p>
+<aside>
+When using <a class="reference external" href="https://code.google.com/p/naclports">naclports</a> or other prebuilt static libraries, you&#8217;ll want
+to make sure you rebuild these libraries with exception handling
+enabled. For naclports, you&#8217;ll want to modify the port&#8217;s <code>build.sh</code>.
+</aside>
 <p>NaCl supports full zero-cost C++ exception handling.</p>
 <h2 id="inline-assembly">Inline Assembly</h2>
 <p>Inline assembly isn&#8217;t supported by PNaCl because it isn&#8217;t portable. The
 one current exception is the common compiler barrier idiom
 <code>asm(&quot;&quot;:::&quot;memory&quot;)</code>, which gets transformed to a sequentially
 consistent memory barrier (equivalent to <code>__sync_synchronize()</code>). In
 PNaCl this barrier is only guaranteed to order <code>volatile</code> and atomic
 memory accesses, though in practice the implementation attempts to also
 prevent reordering of memory accesses to objects which may escape.</p>
 <p>PNaCl supports <a class="reference internal" href="#portable-simd-vectors"><em>Portable SIMD Vectors</em></a>,
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 <p>Neither PNaCl nor NaCl currently support asynchronous interruption
 or suspension of threads.</p>
 </li>
 </ul>
 <p>If PNaCl were to support either of these, the interaction of
 <code>volatile</code> and atomics with same-thread signal handling would need
 to be carefully detailed.</p>
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