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165 lines
6.9 KiB
HTML
165 lines
6.9 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<title>Frequently Asked Questions (FAQ)</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="Author" content="Mike Pall">
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<meta name="Copyright" content="Copyright (C) 2005-2009, Mike Pall">
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<meta name="Language" content="en">
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<link rel="stylesheet" type="text/css" href="bluequad.css" media="screen">
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<link rel="stylesheet" type="text/css" href="bluequad-print.css" media="print">
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<style type="text/css">
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dd { margin-left: 1.5em; }
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</style>
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</head>
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<body>
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<div id="site">
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<a href="http://luajit.org"><span>Lua<span id="logo">JIT</span></span></a>
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</div>
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<div id="head">
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<h1>Frequently Asked Questions (FAQ)</h1>
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</div>
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<div id="nav">
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<ul><li>
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<a href="luajit.html">LuaJIT</a>
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<ul><li>
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<a href="install.html">Installation</a>
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</li><li>
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<a href="running.html">Running</a>
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</li><li>
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<a href="api.html">API Extensions</a>
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</li></ul>
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</li><li>
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<a href="status.html">Status</a>
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<ul><li>
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<a href="changes.html">Changes</a>
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</li></ul>
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</li><li>
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<a class="current" href="faq.html">FAQ</a>
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</li><li>
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<a href="http://luajit.org/download.html">Download <span class="ext">»</span></a>
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</li></ul>
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</div>
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<div id="main">
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<dl>
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<dt>Q: Where can I learn more about Lua and LuaJIT?</dt>
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<dd>
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<ul style="padding: 0;">
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<li>The <a href="http://lua.org"><span class="ext">»</span> main Lua.org site</a> has complete
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<a href="http://www.lua.org/docs.html"><span class="ext">»</span> documentation</a> of the language
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and links to books and papers about Lua.</li>
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<li>The community-managed <a href="http://lua-users.org/wiki/"><span class="ext">»</span> Lua Wiki</a>
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has information about diverse topics.</li>
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<li>The primary source of information for the latest developments surrounding
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Lua is the <a href="http://www.lua.org/lua-l.html"><span class="ext">»</span> Lua mailing list</a>.
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You can check out the <a href="http://lua-users.org/lists/lua-l/"><span class="ext">»</span> mailing
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list archive</a> or
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<a href="http://bazar2.conectiva.com.br/mailman/listinfo/lua"><span class="ext">»</span> subscribe</a>
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to the list (you need to be subscribed before posting).<br>
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This is also the place where announcements and discussions about LuaJIT
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take place.</li>
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</ul>
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</dl>
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<dl>
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<dt>Q: Where can I learn more about the compiler technology used by LuaJIT?</dt>
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<dd>
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I'm planning to write more documentation about the internals of LuaJIT.
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In the meantime, please use the following Google Scholar searches
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to find relevant papers:<br>
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Search for: <a href="http://scholar.google.com/scholar?q=Trace+Compiler"><span class="ext">»</span> Trace Compiler</a><br>
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Search for: <a href="http://scholar.google.com/scholar?q=JIT+Compiler"><span class="ext">»</span> JIT Compiler</a><br>
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Search for: <a href="http://scholar.google.com/scholar?q=Dynamic+Language+Optimizations"><span class="ext">»</span> Dynamic Language Optimizations</a><br>
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Search for: <a href="http://scholar.google.com/scholar?q=SSA+Form"><span class="ext">»</span> SSA Form</a><br>
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Search for: <a href="http://scholar.google.com/scholar?q=Linear+Scan+Register+Allocation"><span class="ext">»</span> Linear Scan Register Allocation</a><br>
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Here is a list of the <a href="http://article.gmane.org/gmane.comp.lang.lua.general/58908"><span class="ext">»</span> innovative features in LuaJIT</a>.<br>
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And, you know, reading the source is of course the only way to enlightenment. :-)
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</dd>
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</dl>
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<dl>
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<dt>Q: Why do I get this error: "attempt to index global 'arg' (a nil value)"?<br>
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Q: My vararg functions fail after switching to LuaJIT!</dt>
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<dd>LuaJIT is compatible to the Lua 5.1 language standard. It doesn't
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support the implicit <tt>arg</tt> parameter for old-style vararg
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functions from Lua 5.0.<br>Please convert your code to the
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<a href="http://www.lua.org/manual/5.1/manual.html#2.5.9"><span class="ext">»</span> Lua 5.1
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vararg syntax</a>.</dd>
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</dl>
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<dl>
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<dt>Q: Why do I get this error: "bad FPU precision"?<br>
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<dt>Q: I get weird behavior after initializing Direct3D.<br>
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<dt>Q: Some FPU operations crash after I load a Delphi DLL.<br>
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</dt>
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<dd>
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DirectX/Direct3D (up to version 9) sets the x87 FPU to single-precision
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mode by default. This violates the Windows ABI and interferes with the
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operation of many programs — LuaJIT is affected, too. Please make
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sure you always use the <tt>D3DCREATE_FPU_PRESERVE</tt> flag when
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initializing Direct3D.<br>
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Direct3D version 10 or higher do not show this behavior anymore.
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Consider testing your application with older versions, too.<br>
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Similarly, the Borland/Delphi runtime modifies the FPU control word and
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enables FP exceptions. Of course this violates the Windows ABI, too.
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Please check the Delphi docs for the Set8087CW method.
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</dl>
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<dl>
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<dt>Q: Sometimes Ctrl-C fails to stop my Lua program. Why?</dt>
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<dd>The interrupt signal handler sets a Lua debug hook. But this is
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currently ignored by compiled code (this will eventually be fixed). If
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your program is running in a tight loop and never falls back to the
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interpreter, the debug hook never runs and can't throw the
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"interrupted!" error.<br> In the meantime you have to press Ctrl-C
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twice to get stop your program. That's similar to when it's stuck
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running inside a C function under the Lua interpreter.</dd>
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</dl>
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<dl>
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<dt>Q: Why doesn't my favorite power-patch for Lua apply against LuaJIT?</dt>
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<dd>Because it's a completely redesigned VM and has very little code
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in common with Lua anymore. Also, if the patch introduces changes to
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the Lua semantics, this would need to be reflected everywhere in the
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VM, from the interpreter up to all stages of the compiler.<br> Please
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use only standard Lua language constructs. For many common needs you
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can use source transformations or use wrapper or proxy functions.
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The compiler will happily optimize away such indirections.</dd>
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</dl>
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<dl>
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<dt>Q: Lua runs everywhere. Why doesn't LuaJIT support my CPU?</dt>
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<dd>Because it's a compiler — it needs to generate native
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machine code. This means the code generator must be ported to each
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architecture. And the fast interpreter is written in assembler and
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must be ported, too. This is quite an undertaking.<br> Currently only
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x86 CPUs are supported. x64 support is in the works. Other
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architectures will follow with sufficient demand and/or
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sponsoring.</dd>
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</dl>
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<dl>
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<dt>Q: When will feature X be added? When will the next version be released?</dt>
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<dd>When it's ready.<br>
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C'mon, it's open source — I'm doing it on my own time and you're
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getting it for free. You can either contribute a patch or sponsor
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the development of certain features, if they are important to you.
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</dd>
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</dl>
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<br class="flush">
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</div>
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<div id="foot">
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<hr class="hide">
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Copyright © 2005-2009 Mike Pall
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<span class="noprint">
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·
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<a href="contact.html">Contact</a>
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</span>
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</div>
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</body>
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</html>
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