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3<html>
4<head>
5 <title>System Library</title>
6 <link rel="stylesheet" href="llvm.css" type="text/css">
7</head>
8<body>
9
10<div class="doc_title"> System Library</div>
11
12<div class="doc_warning">Warning: This document is a work in progress.</div>
13
14<ul>
15 <li><a href="#abstract">Abstract</a></li>
16 <li><a href="#requirements">System Library Requirements</a>
17 <ol>
18 <li><a href="#headers">Hide System Header Files</a></li>
19 <li><a href="#nofunc">No Exposed Functions</a></li>
20 <li><a href="#nodata">No Exposed Data</a></li>
21 <li><a href="#xcptns">No Exceptions</a></li>
22 <li><a href="#errors">Standard Error Codes</a></li>
23 <li><a href="#overhead">Minimize Overhead</a></li>
24 </ol></li>
25 <li><a href="#design">System Library Design</a>
26 <ol>
27 <li><a href="#opaque">Use Opaque Classes</a></li>
28 <li><a href="#common">Common Implementations</a></li>
29 <li><a href="#multi_imps">Multiple Implementations</a></li>
30 <li><a href="#lowlevel">Use Low Level Interfaces</a></li>
31 <li><a href="#memalloc">No Memory Allocation</a></li>
32 <li><a href="#virtuals">No Virtual Methods</a></li>
33 </ol></li>
34 <li><a href="#detail">System Library Details</a>
35 <ol>
36 <li><a href="#bug">Tracking Bugzilla Bug: 351</a></li>
37 <li><a href="#refimpl">Reference Implementatation</a></li>
38 </ol></li>
39</ul>
40
41<div class="doc_author">
42 <p>Written by the <a href="rspencer@x10sys.com">Reid Spencer</a></p>
43</div>
44
45
46<!-- *********************************************************************** -->
47<div class="doc_section"><a name="abstract">Abstract</a></div>
48<div class="doc_text">
49 <p>This document describes the requirements, design, and implementation
50 details of LLVM's System Library. The library is composed of the header files
51 in <tt>llvm/include/llvm/System</tt> and the source files in
52 <tt>llvm/lib/System</tt>. The goal of this library is to completely shield
53 LLVM from the variations in operating system interfaces. By centralizing
54 LLVM's use of operating system interfaces, we make it possible for the LLVM
55 tool chain and runtime libraries to be more easily ported to new platforms.
56 The library also unclutters the rest of LLVM from #ifdef use and special
57 cases for specific operating systems.</p>
58 <p>The System Library was donated to LLVM by Reid Spencer who formulated the
59 original design as part of the eXtensible Programming System (XPS) which is
60 based, in part, on LLVM.</p>
61</div>
62
63<!-- *********************************************************************** -->
64<div class="doc_section">
65 <a name="requirements">System Library Requirements</a>
66</div>
67<div class="doc_text">
68 <p>The System library's requirements are aimed at shielding LLVM from the
69 variations in operating system interfaces. The following sections define the
70 requirements needed to fulfill this objective.</p>
71</div>
72
73<!-- ======================================================================= -->
74<div class="doc_subsection"><a name="headers">Hide System Header Files</a></div>
75<div class="doc_text">
76 <p>To be written.</p>
77</div>
78
79<!-- ======================================================================= -->
80<div class="doc_subsection"><a name="nofunc">No Exposed Functions</a></div>
81<div class="doc_text">
82 <p>To be written.</p>
83</div>
84
85<!-- ======================================================================= -->
86<div class="doc_subsection"><a name="nodata">No Exposed Data</a></div>
87<div class="doc_text">
88 <p>To be written.</p>
89</div>
90
91<!-- ======================================================================= -->
92<div class="doc_subsection"><a name="xcptns">No Exceptions</a></div>
93<div class="doc_text">
94 <p>To be written.</p>
95</div>
96
97<!-- ======================================================================= -->
98<div class="doc_subsection"><a name="errors">Standard Error Codes</a></div>
99<div class="doc_text">
100 <p>To be written.</p>
101</div>
102
103<!-- ======================================================================= -->
104<div class="doc_subsection"><a name="overhead">Minimize Overhead</a></div>
105<div class="doc_text">
106 <p>To be written.</p>
107</div>
108
109<!-- *********************************************************************** -->
110<div class="doc_section"><a name="design">System Library Design</a></div>
111<div class="doc_text">
112 <p>In order to fulfill the requirements of the system library, strict design
113 objectives must be maintained in the library as it evolves. The goal here
114 is to provide interfaces to operating system concepts (files, memory maps,
115 sockets, signals, locking, etc) efficiently and in such a way that the
116 remainder of LLVM is completely operating system agnostic.</p>
117</div>
118
119<!-- ======================================================================= -->
120<div class="doc_subsection"><a name="opaque">Use Opaque Classes</a></div>
121<div class="doc_text">
122 <p>no public data</p>
123 <p>onlyprimitive typed private/protected data</p>
124 <p>data size is "right" for platform, not max of all platforms</p>
125 <p>each class corresponds to O/S concept</p>
126</div>
127
128<!-- ======================================================================= -->
129<div class="doc_subsection"><a name="common">Common Implementations</a></div>
130<div class="doc_text">
131 <p>To be written.</p>
132</div>
133
134<!-- ======================================================================= -->
135<div class="doc_subsection">
136 <a name="multi_imps">Multiple Implementations</a>
137</div>
138<div class="doc_text">
139 <p>To be written.</p>
140</div>
141
142<!-- ======================================================================= -->
143<div class="doc_subsection">
144 <a name="low_level">Use Low Level Interfaces</a>
145</div>
146<div class="doc_text">
147 <p>To be written.</p>
148</div>
149
150<!-- ======================================================================= -->
151<div class="doc_subsection"><a name="memalloc">No Memory Allocation</a></div>
152<div class="doc_text">
153 <p>To be written.</p>
154</div>
155
156<!-- ======================================================================= -->
157<div class="doc_subsection"><a name="virtuals">No Virtual Methods</a></div>
158<div class="doc_text">
159 <p>To be written.</p>
160</div>
161
162<!-- *********************************************************************** -->
163<div class="doc_section"><a name="detail">System Library Details</a></div>
164<div class="doc_text">
165 <p>To be written.</p>
166</div>
167
168<!-- ======================================================================= -->
169<div class="doc_subsection"><a name="bug">Bug 251</a></div>
170<div class="doc_text">
171 <p>See <a href="http://llvm.cs.uiuc.edu/bugs/show_bug?bug=351">bug 351</a>
172 for further details on the progress of this work</p>
173</div>
174
175<!-- ======================================================================= -->
176<div class="doc_subsection">
177 <a name="refimpl">Reference Implementation</a>
178</div>
179<div class="doc_text">
180 <p>The <tt>linux</tt> implementation of the system library will always be the
181 reference implementation. This means that (a) the concepts defined by the
182 linux must be identically replicated in the other implementations and (b) the
183 linux implementation must always be complete (provide implementations for all
184 concepts).</p>
185</div>
186
187<!-- *********************************************************************** -->
188
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196 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
197 <a href="http://llvm.cs.uiuc.edu">LLVM Compiler Infrastructure</a><br>
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