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@@ -55,7 +55,7 @@ dd { margin-left: 1.5em; }
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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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+<dl id="info">
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<dt>Q: Where can I learn more about LuaJIT and Lua?</dt>
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<dd>
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<ul style="padding: 0;">
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@@ -75,7 +75,7 @@ has information about diverse topics.</li>
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</ul>
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</dl>
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-<dl>
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+<dl id="tech">
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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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@@ -91,7 +91,7 @@ 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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+<dl id="arg">
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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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@@ -101,7 +101,7 @@ functions from Lua 5.0.<br>Please convert your code to the
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vararg syntax</a>.</dd>
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</dl>
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-<dl>
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+<dl id="x87">
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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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@@ -123,7 +123,7 @@ Please check the Delphi docs for the Set8087CW method.
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</dl>
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-<dl>
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+<dl id="ctrlc">
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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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@@ -134,7 +134,31 @@ 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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+<dl id="sandbox">
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+<dt>Q: Can Lua code be safely sandboxed?</dt>
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+<dd>
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+Maybe for an extremly restricted subset of Lua and if you relentlessly
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+scrutinize every single interface function you offer to the untrusted code.<br>
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+
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+Although Lua provides some sandboxing functionality (<tt>setfenv()</tt>, hooks),
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+it's very hard to get this right even for the Lua core libraries. Of course,
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+you'll need to inspect any extension library, too. And there are libraries
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+that are inherently unsafe, e.g. the <a href="ext_ffi.html">FFI library</a>.<br>
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+
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+Relatedly, <b>loading untrusted bytecode is not safe!</b> It's trivial
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+to crash the Lua or LuaJIT VM with maliciously crafted bytecode. This is
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+well known and there's no bytecode verification on purpose, so please
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+don't report a bug about it. Check the <tt>mode</tt> parameter for the
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+<tt>load*()</tt> functions to disable loading of bytecode.<br>
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+
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+In general, the only promising approach is to sandbox Lua code at the
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+process level and not the VM level.<br>
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+
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+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)">Wikipedia</a>.
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+</dd>
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+</dl>
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+
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+<dl id="patches">
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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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@@ -145,7 +169,7 @@ 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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+<dl id="arch">
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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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@@ -156,7 +180,7 @@ architectures. Other architectures will follow based on sufficient user
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demand and/or sponsoring.</dd>
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</dl>
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-<dl>
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+<dl id="when">
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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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Mike Pall