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=pod
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LuaJIT
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=head1 Frequently Asked Questions (FAQ)
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=over
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=item * LuaJIT
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=over
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=item * Download E<rchevron>
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=item * Installation
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=item * Running
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=back
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=item * Extensions
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=over
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=item * FFI Library
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=over
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=item * FFI Tutorial
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=item * ffi.* API
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=item * FFI Semantics
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=back
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=item * jit.* Library
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=item * Lua/C API
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=item * Profiler
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=back
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=item * Status
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=over
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=item * Changes
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=back
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=item * FAQ
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=item * Performance E<rchevron>
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=item * Wiki E<rchevron>
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=item * Mailing List E<rchevron>
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=back
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=over
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=item Q: Where can I learn more about LuaJIT and Lua?
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=over
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=item * The E<rchevron> LuaJIT mailing list focuses on topics related
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to LuaJIT.
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=item * The E<rchevron> LuaJIT wiki gathers community resources about
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LuaJIT.
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=item * News about Lua itself can be found at the E<rchevron> Lua
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mailing list. The mailing list archives are worth checking out for
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older postings about LuaJIT.
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=item * The E<rchevron> main Lua.org site has complete E<rchevron>
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documentation of the language and links to books and papers about Lua.
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=item * The community-managed E<rchevron> Lua Wiki has information
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about diverse topics.
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=back
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=back
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=over
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=item Q: Where can I learn more about the compiler technology used by
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LuaJIT?
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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 to
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find relevant papers:
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Search for: E<rchevron> Trace Compiler
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Search for: E<rchevron> JIT Compiler
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Search for: E<rchevron> Dynamic Language Optimizations
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Search for: E<rchevron> SSA Form
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Search for: E<rchevron> Linear Scan Register Allocation
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Here is a list of the E<rchevron> innovative features in LuaJIT.
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And, you know, reading the source is of course the only way to
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enlightenment. :-)
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=back
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=over
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=item Q: Why do I get this error: "attempt to index global 'arg' (a nil
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value)"?
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Q: My vararg functions fail after switching to LuaJIT!
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LuaJIT is compatible to the Lua 5.1 language standard. It doesn't
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support the implicit C<arg> parameter for old-style vararg functions
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from Lua 5.0.
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Please convert your code to the E<rchevron> Lua 5.1 vararg syntax.
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=back
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=over
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=item Q: Why do I get this error: "bad FPU precision"?
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=item Q: I get weird behavior after initializing Direct3D.
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=item Q: Some FPU operations crash after I load a Delphi DLL.
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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 E<mdash> LuaJIT is affected, too. Please
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make sure you always use the C<D3DCREATE_FPU_PRESERVE> flag when
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initializing Direct3D.
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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.
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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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=back
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=over
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=item Q: Sometimes Ctrl-C fails to stop my Lua program. Why?
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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.
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In the meantime you have to press Ctrl-C twice to get stop your
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program. That's similar to when it's stuck running inside a C function
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under the Lua interpreter.
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=back
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=over
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=item Q: Why doesn't my favorite power-patch for Lua apply against
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LuaJIT?
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Because it's a completely redesigned VM and has very little code in
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common with Lua anymore. Also, if the patch introduces changes to the
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Lua semantics, these would need to be reflected everywhere in the VM,
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from the interpreter up to all stages of the compiler.
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Please use only standard Lua language constructs. For many common needs
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you can use source transformations or use wrapper or proxy functions.
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The compiler will happily optimize away such indirections.
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=back
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=over
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=item Q: Lua runs everywhere. Why doesn't LuaJIT support my CPU?
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Because it's a compiler E<mdash> it needs to generate native machine
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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 must
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be ported, too. This is quite an undertaking.
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The install documentation shows the supported architectures. Other
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architectures will follow based on sufficient user demand and/or
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sponsoring.
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=back
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=over
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=item Q: When will feature X be added? When will the next version be
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released?
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When it's ready.
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C'mon, it's open source E<mdash> 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 the
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development of certain features, if they are important to you.
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=back
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----
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Copyright E<copy> 2005-2017 Mike Pall E<middot> Contact
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=cut
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#Pod::HTML2Pod conversion notes:
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#From file faq.html
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# 7685 bytes of input
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#Sat May 13 16:35:32 2017 agentzh
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# No a_name switch not specified, so will not try to render <a name='...'>
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# No a_href switch not specified, so will not try to render <a href='...'>
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