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265 lines
6.6 KiB
HTML
265 lines
6.6 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML>
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<HEAD>
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<link rel="stylesheet" href="designstyle.css">
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<title>Google CPU Profiler Binary Data File Format</title>
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</HEAD>
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<BODY>
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<h1>Google CPU Profiler Binary Data File Format</h1>
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<p align=right>
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<i>Last modified
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<script type=text/javascript>
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var lm = new Date(document.lastModified);
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document.write(lm.toDateString());
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</script></i>
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</p>
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<p>This file documents the binary data file format produced by the
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Google CPU Profiler. For information about using the CPU Profiler,
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see <a href="cpuprofile.html">its user guide</a>.
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<p>The profiler source code, which generates files using this format, is at
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<code>src/profiler.cc</code></a>.
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<h2>CPU Profile Data File Structure</h2>
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<p>CPU profile data files each consist of four parts, in order:
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<ul>
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<li> Binary header
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<li> Binary profile records
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<li> Binary trailer
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<li> Text list of mapped objects
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</ul>
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<p>The binary data is expressed in terms of "slots." These are words
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large enough to hold the program's pointer type, i.e., for 32-bit
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programs they are 4 bytes in size, and for 64-bit programs they are 8
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bytes. They are stored in the profile data file in the native byte
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order (i.e., little-endian for x86 and x86_64).
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<h2>Binary Header</h2>
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<p>The binary header format is show below. Values written by the
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profiler, along with requirements currently enforced by the analysis
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tools, are shown in parentheses.
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<p>
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<table summary="Header Format"
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frame="box" rules="sides" cellpadding="5" width="50%">
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<tr>
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<th width="30%">slot</th>
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<th width="70%">data</th>
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</tr>
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<tr>
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<td>0</td>
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<td>header count (0; must be 0)</td>
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</tr>
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<tr>
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<td>1</td>
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<td>header slots after this one (3; must be >= 3)</td>
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</tr>
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<tr>
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<td>2</td>
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<td>format version (0; must be 0)</td>
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</tr>
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<tr>
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<td>3</td>
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<td>sampling period, in microseconds</td>
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</tr>
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<tr>
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<td>4</td>
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<td>padding (0)</td>
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</tr>
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</table>
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<p>The headers currently generated for 32-bit and 64-bit little-endian
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(x86 and x86_64) profiles are shown below, for comparison.
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<p>
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<table summary="Header Example" frame="box" rules="sides" cellpadding="5">
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<tr>
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<th></th>
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<th>hdr count</th>
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<th>hdr words</th>
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<th>version</th>
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<th>sampling period</th>
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<th>pad</th>
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</tr>
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<tr>
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<td>32-bit or 64-bit (slots)</td>
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<td>0</td>
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<td>3</td>
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<td>0</td>
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<td>10000</td>
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<td>0</td>
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</tr>
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<tr>
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<td>32-bit (4-byte words in file)</td>
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<td><tt>0x00000</tt></td>
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<td><tt>0x00003</tt></td>
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<td><tt>0x00000</tt></td>
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<td><tt>0x02710</tt></td>
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<td><tt>0x00000</tt></td>
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</tr>
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<tr>
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<td>64-bit LE (4-byte words in file)</td>
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<td><tt>0x00000 0x00000</tt></td>
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<td><tt>0x00003 0x00000</tt></td>
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<td><tt>0x00000 0x00000</tt></td>
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<td><tt>0x02710 0x00000</tt></td>
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<td><tt>0x00000 0x00000</tt></td>
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</tr>
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</table>
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<p>The contents are shown in terms of slots, and in terms of 4-byte
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words in the profile data file. The slot contents for 32-bit and
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64-bit headers are identical. For 32-bit profiles, the 4-byte word
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view matches the slot view. For 64-bit profiles, each (8-byte) slot
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is shown as two 4-byte words, ordered as they would appear in the
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file.
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<p>The profiling tools examine the contents of the file and use the
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expected locations and values of the header words field to detect
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whether the file is 32-bit or 64-bit.
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<h2>Binary Profile Records</h2>
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<p>The binary profile record format is shown below.
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<p>
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<table summary="Profile Record Format"
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frame="box" rules="sides" cellpadding="5" width="50%">
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<tr>
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<th width="30%">slot</th>
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<th width="70%">data</th>
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</tr>
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<tr>
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<td>0</td>
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<td>sample count, must be >= 1</td>
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</tr>
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<tr>
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<td>1</td>
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<td>number of call chain PCs (num_pcs), must be >= 1</td>
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</tr>
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<tr>
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<td>2 .. (num_pcs + 1)</td>
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<td>call chain PCs, most-recently-called function first.
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</tr>
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</table>
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<p>The total length of a given record is 2 + num_pcs.
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<p>Note that multiple profile records can be emitted by the profiler
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having an identical call chain. In that case, analysis tools should
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sum the counts of all records having identical call chains.
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<p><b>Note:</b> Some profile analysis tools terminate if they see
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<em>any</em> profile record with a call chain with its first entry
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having the address 0. (This is similar to the binary trailer.)
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<h3>Example</h3>
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This example shows the slots contained in a sample profile record.
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<p>
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<table summary="Profile Record Example"
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frame="box" rules="sides" cellpadding="5">
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<tr>
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<td>5</td>
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<td>3</td>
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<td>0xa0000</td>
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<td>0xc0000</td>
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<td>0xe0000</td>
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</tr>
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</table>
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<p>In this example, 5 ticks were received at PC 0xa0000, whose
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function had been called by the function containing 0xc0000, which had
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been called from the function containing 0xe0000.
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<h2>Binary Trailer</h2>
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<p>The binary trailer consists of three slots of data with fixed
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values, shown below.
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<p>
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<table summary="Trailer Format"
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frame="box" rules="sides" cellpadding="5" width="50%">
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<tr>
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<th width="30%">slot</th>
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<th width="70%">value</th>
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</tr>
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<tr>
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<td>0</td>
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<td>0</td>
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</tr>
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<tr>
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<td>1</td>
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<td>1</td>
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</tr>
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<tr>
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<td>2</td>
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<td>0</td>
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</tr>
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</table>
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<p>Note that this is the same data that would contained in a profile
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record with sample count = 0, num_pcs = 1, and a one-element call
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chain containing the address 0.
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<h2>Text List of Mapped Objects</h2>
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<p>The binary data in the file is followed immediately by a list of
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mapped objects. This list consists of lines of text separated by
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newline characters.
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<p>Each line is one of the following types:
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<ul>
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<li>Build specifier, starting with "<tt>build=</tt>". For example:
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<pre> build=/path/to/binary</pre>
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Leading spaces on the line are ignored.
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<li>Mapping line from ProcMapsIterator::FormatLine. For example:
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<pre> 40000000-40015000 r-xp 00000000 03:01 12845071 /lib/ld-2.3.2.so</pre>
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The first address must start at the beginning of the line.
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</ul>
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<p>Unrecognized lines should be ignored by analysis tools.
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<p>When processing the paths see in mapping lines, occurrences of
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<tt>$build</tt> followed by a non-word character (i.e., characters
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other than underscore or alphanumeric characters), should be replaced
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by the path given on the last build specifier line.
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<hr>
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<address>Chris Demetriou<br>
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<!-- Created: Mon Aug 27 12:18:26 PDT 2007 -->
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<!-- hhmts start -->
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Last modified: Mon Aug 27 12:18:26 PDT 2007 (cgd)
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<!-- hhmts end -->
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</address>
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</BODY>
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</HTML>
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