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diff --git a/libs/luajit-cmake/luajit/doc/faq.html b/libs/luajit-cmake/luajit/doc/faq.html new file mode 100644 index 0000000..c07fd24 --- /dev/null +++ b/libs/luajit-cmake/luajit/doc/faq.html @@ -0,0 +1,195 @@ +<!DOCTYPE html> +<html> +<head> +<title>Frequently Asked Questions (FAQ)</title> +<meta charset="utf-8"> +<meta name="Copyright" content="Copyright (C) 2005-2022"> +<meta name="Language" content="en"> +<link rel="stylesheet" type="text/css" href="bluequad.css" media="screen"> +<link rel="stylesheet" type="text/css" href="bluequad-print.css" media="print"> +<style type="text/css"> +dd { margin-left: 1.5em; } +</style> +</head> +<body> +<div id="site"> +<a href="https://luajit.org"><span>Lua<span id="logo">JIT</span></span></a> +</div> +<div id="head"> +<h1>Frequently Asked Questions (FAQ)</h1> +</div> +<div id="nav"> +<ul><li> +<a href="luajit.html">LuaJIT</a> +<ul><li> +<a href="https://luajit.org/download.html">Download <span class="ext">»</span></a> +</li><li> +<a href="install.html">Installation</a> +</li><li> +<a href="running.html">Running</a> +</li></ul> +</li><li> +<a href="extensions.html">Extensions</a> +<ul><li> +<a href="ext_ffi.html">FFI Library</a> +<ul><li> +<a href="ext_ffi_tutorial.html">FFI Tutorial</a> +</li><li> +<a href="ext_ffi_api.html">ffi.* API</a> +</li><li> +<a href="ext_ffi_semantics.html">FFI Semantics</a> +</li></ul> +</li><li> +<a href="ext_buffer.html">String Buffers</a> +</li><li> +<a href="ext_jit.html">jit.* Library</a> +</li><li> +<a href="ext_c_api.html">Lua/C API</a> +</li><li> +<a href="ext_profiler.html">Profiler</a> +</li></ul> +</li><li> +<a href="status.html">Status</a> +</li><li> +<a class="current" href="faq.html">FAQ</a> +</li><li> +<a href="https://luajit.org/list.html">Mailing List <span class="ext">»</span></a> +</li></ul> +</div> +<div id="main"> +<dl id="info"> +<dt>Q: Where can I learn more about LuaJIT and Lua?</dt> +<dd> +<ul style="padding: 0;"> +<li>The <a href="https://luajit.org/list.html"><span class="ext">»</span> LuaJIT mailing list</a> focuses on topics +related to LuaJIT.</li> +<li>News about Lua itself can be found at the +<a href="https://www.lua.org/lua-l.html"><span class="ext">»</span> Lua mailing list</a>. +The mailing list archives are worth checking out for older postings +about LuaJIT.</li> +<li>The <a href="https://lua.org"><span class="ext">»</span> main Lua.org site</a> has complete +<a href="https://www.lua.org/docs.html"><span class="ext">»</span> documentation</a> of the language +and links to books and papers about Lua.</li> +<li>The community-managed <a href="http://lua-users.org/wiki/"><span class="ext">»</span> Lua Wiki</a> +has information about diverse topics.</li> +</ul></dd> +</dl> + +<dl id="tech"> +<dt>Q: Where can I learn more about the compiler technology used by LuaJIT?</dt> +<dd> +Please use the following Google Scholar searches to find relevant papers:<br> +Search for: <a href="https://scholar.google.com/scholar?q=Trace+Compiler"><span class="ext">»</span> Trace Compiler</a><br> +Search for: <a href="https://scholar.google.com/scholar?q=JIT+Compiler"><span class="ext">»</span> JIT Compiler</a><br> +Search for: <a href="https://scholar.google.com/scholar?q=Dynamic+Language+Optimizations"><span class="ext">»</span> Dynamic Language Optimizations</a><br> +Search for: <a href="https://scholar.google.com/scholar?q=SSA+Form"><span class="ext">»</span> SSA Form</a><br> +Search for: <a href="https://scholar.google.com/scholar?q=Linear+Scan+Register+Allocation"><span class="ext">»</span> Linear Scan Register Allocation</a><br> +Here is a list of the <a href="http://lua-users.org/lists/lua-l/2009-11/msg00089.html"><span class="ext">»</span> innovative features in LuaJIT</a>.<br> +And, you know, reading the source is of course the only way to enlightenment. +</dd> +</dl> + +<dl id="arg"> +<dt>Q: Why do I get this error: "attempt to index global 'arg' (a nil value)"?<br> +Q: My vararg functions fail after switching to LuaJIT!</dt> +<dd>LuaJIT is compatible to the Lua 5.1 language standard. It doesn't +support the implicit <tt>arg</tt> parameter for old-style vararg +functions from Lua 5.0.<br>Please convert your code to the +<a href="https://www.lua.org/manual/5.1/manual.html#2.5.9"><span class="ext">»</span> Lua 5.1 +vararg syntax</a>.</dd> +</dl> + +<dl id="x87"> +<dt>Q: Why do I get this error: "bad FPU precision"?<br> +<dt>Q: I get weird behavior after initializing Direct3D.<br> +<dt>Q: Some FPU operations crash after I load a Delphi DLL.<br> +</dt> +<dd> + +DirectX/Direct3D (up to version 9) sets the x87 FPU to single-precision +mode by default. This violates the Windows ABI and interferes with the +operation of many programs — LuaJIT is affected, too. Please make +sure you always use the <tt>D3DCREATE_FPU_PRESERVE</tt> flag when +initializing Direct3D.<br> + +Direct3D version 10 or higher do not show this behavior anymore. +Consider testing your application with older versions, too.<br> + +Similarly, the Borland/Delphi runtime modifies the FPU control word and +enables FP exceptions. Of course, this violates the Windows ABI, too. +Please check the Delphi docs for the Set8087CW method.</dd> +</dl> + +<dl id="ctrlc"> +<dt>Q: Sometimes Ctrl-C fails to stop my Lua program. Why?</dt> +<dd>The interrupt signal handler sets a Lua debug hook. But this is +ignored by compiled code. If your program is running in a tight loop +and never falls back to the interpreter, the debug hook never runs and +can't throw the "interrupted!" error.<br> +You have to press Ctrl-C twice to stop your program. That's similar +to when it's stuck running inside a C function under the Lua interpreter.</dd> +</dl> + +<dl id="order"> +<dt>Q: Table iteration with <tt>pairs()</tt> does not result in the same order?</dt> +<dd>The order of table iteration is explicitly <b>undefined</b> by +the Lua language standard.<br> +Different Lua implementations or versions may use different orders for +otherwise identical tables. Different ways of constructing a table may +result in different orders, too.<br> +Due to improved VM security, LuaJIT 2.1 may even use a different order +on separate VM invocations or when string keys are newly interned.<br><br> +If your program relies on a deterministic order, it has a bug. Rewrite it, +so it doesn't rely on the key order. Or sort the table keys, if you must.</dd> +</dl> + +<dl id="sandbox"> +<dt>Q: Can Lua code be safely sandboxed?</dt> +<dd> +Maybe for an extremely restricted subset of Lua and if you relentlessly +scrutinize every single interface function you offer to the untrusted code.<br> + +Although Lua provides some sandboxing functionality (<tt>setfenv()</tt>, hooks), +it's very hard to get this right even for the Lua core libraries. Of course, +you'll need to inspect any extension library, too. And there are libraries +that are inherently unsafe, e.g. the <a href="ext_ffi.html">FFI library</a>.<br> + +More reading material at the <a href="http://lua-users.org/wiki/SandBoxes"><span class="ext">»</span> Lua Wiki</a> and <a href="https://en.wikipedia.org/wiki/Sandbox_(computer_security)"><span class="ext">»</span> Wikipedia</a>.<br><br> + +Relatedly, <b>loading untrusted bytecode is not safe!</b><br> + +It's trivial to crash the Lua or LuaJIT VM with maliciously crafted bytecode. +This is well known and there's no bytecode verification on purpose, so please +don't report a bug about it. Check the <tt>mode</tt> parameter for the +<tt>load*()</tt> functions to disable loading of bytecode.<br><br> + +<b>In general, the only promising approach is to sandbox Lua code at the +process level and not the VM level.</b> +</dd> +</dl> + +<dl id="arch"> +<dt>Q: Lua runs everywhere. Why doesn't LuaJIT support my CPU?</dt> +<dd>Because it's a compiler — it needs to generate native +machine code. This means the code generator must be ported to each +architecture. And the fast interpreter is written in assembler and +must be ported, too. This is quite an undertaking.<br> +The <a href="install.html">install documentation</a> shows the supported +architectures.<br> +Other architectures may follow based on sufficient user demand and +market-relevance of the architecture. Sponsoring is required to develop +the port itself, to integrate it and to continuously maintain it in the +actively developed branches.</dd> +</dl> +<br class="flush"> +</div> +<div id="foot"> +<hr class="hide"> +Copyright © 2005-2022 +<span class="noprint"> +· +<a href="contact.html">Contact</a> +</span> +</div> +</body> +</html> |