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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>Portability Requirements for Coco</title><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><meta name="Author" content="Mike Pall"><meta name="Copyright" content="Copyright (C) 2005-2007, Mike Pall"><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">table.support { line-height: 1.2; width: 25em;}tr.supporthead td { font-weight: bold;}td.supportcpu { width: 6em;}td.supportsys { width: 8em;}</style></head><body><div id="site"><a href="http://luajit.org/"><span>Lua<span id="logo">JIT</span></span></a></div><div id="head"><h1>Portability Requirements for Coco</h1></div><div id="nav"><ul><li><a href="index.html">Index</a></li><li><a href="luajit.html">LuaJIT</a><ul><li><a href="luajit_features.html">Features</a></li><li><a href="luajit_install.html">Installation</a></li><li><a href="luajit_run.html">Running</a></li><li><a href="luajit_api.html">API Extensions</a></li><li><a href="luajit_intro.html">Introduction</a></li><li><a href="luajit_performance.html">Performance</a></li><li><a href="luajit_debug.html">Debugging</a></li><li><a href="luajit_changes.html">Changes</a></li></ul></li><li><a href="coco.html">Coco</a><ul><li><a class="current" href="coco_portability.html">Portability</a></li><li><a href="coco_api.html">API Extensions</a></li><li><a href="coco_changes.html">Changes</a></li></ul></li><li><a href="dynasm.html">DynASM</a><ul><li><a href="dynasm_features.html">Features</a></li><li><a href="dynasm_examples.html">Examples</a></li></ul></li><li><a href="http://luajit.org/download.html">Download <span class="ext">»</span></a></li></ul></div><div id="main"><p>Coco needs some machine-specific features which areinherently non-portable. Although the coverage is pretty good,this means that Coco will probably never be a standard partof the Lua core (which is pure ANSI C).</p><h2>Context Switching Methods</h2><p>Coco relies on four different machine-specific methodsfor allocating a C stack and switching context.The appropriate method is automatically selected at compile time.</p><h3>GCC Inline Assembler</h3><p>This method is only available when GCC 3.x/4.x is usedto compile the source.This is the fastest method for context switching, but only availablefor a few CPUs (see below).</p><h3>Modified setjmp Buffer</h3><p>This method changes a few fields in the setjmp buffer toredirect the next longjmp to a new function with a new stackframe. It needs a bit of guesswork and lots of #ifdef's tohandle the supported CPU/OS combinations, but this is quitemanageable.</p><p>This is the fallback method if inline assembler is not available.It's pretty fast because it doesn't have to save or restore signals(which is slow and generally undesirable for Lua coroutines).</p><h3>POSIX ucontext</h3><p>The POSIX calls getcontext, makecontext and switchcontextare used to set up and switch between different C stacks.Although highly portable and even available for someesoteric platforms, it's slower than the setjmp methodbecause it saves and restores signals, too (using at least onesyscall for each context switch).</p><p>You can force the use of ucontext (instead of setjmp) by enabling<tt>-DCOCO_USE_UCONTEXT</tt> in <tt>src/Makefile</tt>.</p><h3>Windows Fibers</h3><p>This is the standard method to set up and switch betweendifferent C stacks on Windows. It's available on Windows 98and later.</p><p>None of the other methods work for Windows because OS specific codeis required to switch exception handling contexts.</p><h2 class="pagebreak">Supported Platforms</h2><p>Coco has support for the following platforms:</p><table class="support"><tr class="supporthead"><td class="supportcpu">CPU</td><td class="supportsys">System</td><td>Method</td></tr><tr class="odd separate"><td class="supportcpu">x86</td><td class="supportsys">*</td><td>gccasm</td></tr><tr class="even"><td class="supportcpu">x86</td><td class="supportsys">Linux</td><td>setjmp</td></tr><tr class="odd"><td class="supportcpu">x86</td><td class="supportsys">FreeBSD</td><td>setjmp</td></tr><tr class="even"><td class="supportcpu">x86</td><td class="supportsys">NetBSD</td><td>setjmp</td></tr><tr class="odd"><td class="supportcpu">x86</td><td class="supportsys">OpenBSD</td><td>setjmp</td></tr><tr class="even"><td class="supportcpu">x86</td><td class="supportsys">Solaris</td><td>setjmp</td></tr><tr class="odd"><td class="supportcpu">x86</td><td class="supportsys">Mac OS X</td><td>setjmp</td></tr><tr class="even separate"><td class="supportcpu">x64</td><td class="supportsys">Linux</td><td>setjmp</td></tr><tr class="odd"><td class="supportcpu">x64</td><td class="supportsys">Solaris</td><td>setjmp</td></tr><tr class="even separate"><td class="supportcpu">MIPS32</td><td class="supportsys">*</td><td>gccasm</td></tr><tr class="odd"><td class="supportcpu">MIPS32</td><td class="supportsys">Linux</td><td>setjmp</td></tr><tr class="even separate"><td class="supportcpu">ARM</td><td class="supportsys">Linux</td><td>setjmp</td></tr><tr class="odd separate"><td class="supportcpu">PPC32</td><td class="supportsys">Mac OS X</td><td>setjmp</td></tr><tr class="even separate"><td class="supportcpu">*</td><td class="supportsys">POSIX</td><td>ucontext</td></tr><tr class="odd separate"><td class="supportcpu">*</td><td class="supportsys">Windows</td><td>fibers</td></tr></table><pre></pre><p>It should work pretty much anywhere where a <em>correct</em>POSIX ucontext implementation is available. It has been testedon every systems I could get hold of (e.g. Sparc, PPC32/PPC64,IA64, Alpha, HPPA with various operating systems).</p><h2>Caveats</h2><ul><li>Some older operating systems may have defective ucontextimplementations because this feature is not widely used. E.g. someimplementations don't mix well with other C library functionslike <tt>malloc()</tt> or with native threads.This is really not the fault of Coco — please upgrade your OS.</li><li>Note for Windows: Please read the explanation for the default<a href="http://msdn.microsoft.com/library/en-us/dllproc/base/thread_stack_size.asp"><span class="ext">»</span> Thread Stack Size</a>in case you want to create large numbers of Fiber-based coroutines.</li><li>Note for MinGW/Cygwin: Older releases of GCC (before 4.0) generatewrong unwind information when <tt>-fomit-frame-pointer</tt> is usedwith stdcalls. This may lead to crashes when exceptions are thrown.The workaround is to always use two flags:<br><tt>-fomit-frame-pointer -maccumulate-outgoing-args</tt>.</li><li>Note for MIPS CPUs without FPU: It's recommended to compile<em>all</em> sources with <tt>-msoft-float</tt>, even if you don't useany floating point ops anywhere. Otherwise context switching mustsave and restore FPU registers (which needs to go throughthe slow kernel emulation).</li><li>To run Coco with <a href="http://valgrind.org/"><span class="ext">»</span> Valgrind</a>(a memory debugger) you <em>must</em> add <tt>-DUSE_VALGRIND</tt>to <tt>MYCFLAGS</tt> and recompile. You will get random errorsif you don't! Valgrind 3.x or later is required. Earlier versionsdo not work well with newly allocated C stacks.</li></ul><br class="flush"></div><div id="foot"><hr class="hide">Copyright © 2005-2007 Mike Pall<span class="noprint">·<a href="contact.html">Contact</a></span></div></body></html>⌨️ 快捷键说明
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