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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
+<html>
+<head>
+ <title>System Library</title>
+ <link rel="stylesheet" href="llvm.css" type="text/css">
+</head>
+<body>
+
+<div class="doc_title"> System Library</div>
+
+<div class="doc_warning">Warning: This document is a work in progress.</div>
+
+<ul>
+ <li><a href="#abstract">Abstract</a></li>
+ <li><a href="#requirements">System Library Requirements</a>
+ <ol>
+ <li><a href="#headers">Hide System Header Files</a></li>
+ <li><a href="#nofunc">No Exposed Functions</a></li>
+ <li><a href="#nodata">No Exposed Data</a></li>
+ <li><a href="#xcptns">No Exceptions</a></li>
+ <li><a href="#errors">Standard Error Codes</a></li>
+ <li><a href="#overhead">Minimize Overhead</a></li>
+ </ol></li>
+ <li><a href="#design">System Library Design</a>
+ <ol>
+ <li><a href="#opaque">Use Opaque Classes</a></li>
+ <li><a href="#common">Common Implementations</a></li>
+ <li><a href="#multi_imps">Multiple Implementations</a></li>
+ <li><a href="#lowlevel">Use Low Level Interfaces</a></li>
+ <li><a href="#memalloc">No Memory Allocation</a></li>
+ <li><a href="#virtuals">No Virtual Methods</a></li>
+ </ol></li>
+ <li><a href="#detail">System Library Details</a>
+ <ol>
+ <li><a href="#bug">Tracking Bugzilla Bug: 351</a></li>
+ <li><a href="#refimpl">Reference Implementatation</a></li>
+ </ol></li>
+</ul>
+
+<div class="doc_author">
+ <p>Written by the <a href="rspencer@x10sys.com">Reid Spencer</a></p>
+</div>
+
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="abstract">Abstract</a></div>
+<div class="doc_text">
+ <p>This document describes the requirements, design, and implementation
+ details of LLVM's System Library. The library is composed of the header files
+ in <tt>llvm/include/llvm/System</tt> and the source files in
+ <tt>llvm/lib/System</tt>. The goal of this library is to completely shield
+ LLVM from the variations in operating system interfaces. By centralizing
+ LLVM's use of operating system interfaces, we make it possible for the LLVM
+ tool chain and runtime libraries to be more easily ported to new platforms.
+ The library also unclutters the rest of LLVM from #ifdef use and special
+ cases for specific operating systems.</p>
+ <p>The System Library was donated to LLVM by Reid Spencer who formulated the
+ original design as part of the eXtensible Programming System (XPS) which is
+ based, in part, on LLVM.</p>
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="requirements">System Library Requirements</a>
+</div>
+<div class="doc_text">
+ <p>The System library's requirements are aimed at shielding LLVM from the
+ variations in operating system interfaces. The following sections define the
+ requirements needed to fulfill this objective.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="headers">Hide System Header Files</a></div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="nofunc">No Exposed Functions</a></div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="nodata">No Exposed Data</a></div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="xcptns">No Exceptions</a></div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="errors">Standard Error Codes</a></div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="overhead">Minimize Overhead</a></div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="design">System Library Design</a></div>
+<div class="doc_text">
+ <p>In order to fulfill the requirements of the system library, strict design
+ objectives must be maintained in the library as it evolves. The goal here
+ is to provide interfaces to operating system concepts (files, memory maps,
+ sockets, signals, locking, etc) efficiently and in such a way that the
+ remainder of LLVM is completely operating system agnostic.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="opaque">Use Opaque Classes</a></div>
+<div class="doc_text">
+ <p>no public data</p>
+ <p>onlyprimitive typed private/protected data</p>
+ <p>data size is "right" for platform, not max of all platforms</p>
+ <p>each class corresponds to O/S concept</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="common">Common Implementations</a></div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="multi_imps">Multiple Implementations</a>
+</div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="low_level">Use Low Level Interfaces</a>
+</div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="memalloc">No Memory Allocation</a></div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="virtuals">No Virtual Methods</a></div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="detail">System Library Details</a></div>
+<div class="doc_text">
+ <p>To be written.</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="bug">Bug 251</a></div>
+<div class="doc_text">
+ <p>See <a href="http://llvm.cs.uiuc.edu/bugs/show_bug?bug=351">bug 351</a>
+ for further details on the progress of this work</p>
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="refimpl">Reference Implementation</a>
+</div>
+<div class="doc_text">
+ <p>The <tt>linux</tt> implementation of the system library will always be the
+ reference implementation. This means that (a) the concepts defined by the
+ linux must be identically replicated in the other implementations and (b) the
+ linux implementation must always be complete (provide implementations for all
+ concepts).</p>
+</div>
+
+<!-- *********************************************************************** -->
+
+<hr>
+<address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a>
+
+ <a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
+ <a href="http://llvm.cs.uiuc.edu">LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date$
+</address>
+</body>
+</html>
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