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1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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2 <HTML>
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3 <HEAD>
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4 <TITLE>ccache</TITLE>
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5 </HEAD>
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6 <BODY BGCOLOR="#ffffff" TEXT="#000000" VLINK="#292555" LINK="#292555" ALINK="#cc0033">
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7 <h2>ccache</h2>
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8
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9 ccache is a compiler cache. It acts as a caching pre-processor to
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10 C/C++ compilers, using the -E compiler switch and a hash to detect
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11 when a compilation can be satisfied from cache. This often results in
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12 a 5 to 10 times speedup in common compilations.<p>
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13
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14 The idea came from Erik Thiele wrote the original <a
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15 href="http://compilercache.sourceforge.net/">compilercache</a> program
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16 as a bourne shell script. ccache is a re-implementation of Erik's idea
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17 in C with more features and better performance.<p>
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18
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19 <h2>Latest release</h2>
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20
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21 The latest release is ccache 2.4.
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22
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23 <ul>
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24 <li>Added CCACHE_READONLY option
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25 <li>Added CCACHE_TEMPDIR option
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26 <li>fixed handling of hard-linked compilers on AIX
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27 <li>added O_BINARY support, to try and support win32 compiles
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28 <li>show cache directory in stats output
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29 <li>fixed handling of HOME environment variable
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30 </ul>
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31
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32 See the <a href="ccache-man.html">manual page</a> for details
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33 on the new options.<p>
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34
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35 You can get this release from the <a href="http://ccache.samba.org/ftp/ccache/">download directory</a>
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36
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37 <p>NOTE! This release changes the hash input slighly, so you will
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38 probably find that you will not get any hits against your existing
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39 cache when you upgrade.
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40
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41 <h2>Why bother?</h2>
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42
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43 Why bother with a compiler cache? If you ever run "make clean; make"
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44 then you can probably benefit from ccache. It is very common for
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45 developers to do a clean build of a project for a whole host of
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46 reasons, and this throws away all the information from your previous
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47 compiles.<p>
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48
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49 By using ccache you can get exactly the same effect as "make clean;
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50 make" but much faster. It also helps a lot when doing RPM builds,
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51 as RPM can make doing incremental builds tricky.<p>
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52
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53 I put the effort into writing ccache for 2 reasons. The first is the
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54 Samba build farm
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55 (<a href="http://build.samba.org/">http://build.samba.org/</a>)
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56 which constantly does clean builds of Samba on about 30 machines after each
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57 CVS commit. On some of those machines the build took over an hour. By
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58 using ccache we get the same effect as clean builds but about 6 times
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59 faster.<p>
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60
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61 The second reason is the autobuild system I used to run for
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62 Quantum. That system builds our whole Linux based OS from scratch
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63 after every CVS commit to catch compilation problems quickly. Using
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64 ccache those builds are much faster.
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65
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66 <h2>Is it safe?</h2>
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67
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68 Yes. The most important aspect of a compiler cache is to <b>always</b>
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69 produce exactly the same output that the real compiler would
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70 produce. The includes providing exactly the same object files and
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71 exactly the same compiler warnings that would be produced if you use
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72 the real compiler. The only way you should be able to tell that you
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73 are using ccache is the speed.<p>
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74
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75 I have coded ccache very carefully to try to provide these guarantees.
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76
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77 <h2>Features</h2>
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78
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79 <ul>
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80 <li> keeps statistics on hits/misses
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81 <li> automatic cache size management
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82 <li> can cache compiles that generate warnings
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83 <li> easy installation
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84 <li> very low overhead
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85 <li> uses hard links where possible to avoid copies
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86 </ul>
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87
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88 <h2>Documentation</h2>
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89
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90 See the <a href="ccache-man.html">manual page</a>
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91
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92
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93 <h2>Performance</h2>
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94
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95 Here are some results for compiling Samba on my Linux laptop. I have
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96 also included the results of using Erik's compilercache program
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97 (version 1.0.10) for comparison.<p>
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98
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99 <table border=1>
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100 <tr><th> </th> <th> ccache</th> <th> compilercache</th> </tr>
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101 <tr><td>normal </td> <td align=right>13m 4s </td><td align=right>13m 4s</td> </tr>
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102 <tr><td>uncached </td> <td align=right>13m 15s </td><td align=right>15m 41s</td> </tr>
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103 <tr><td>cached </td> <td align=right>2m 45s </td><td align=right>4m 26s</td> </tr>
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104 </table>
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105
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106 <h2>How to use it</h2>
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107
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108 You can use ccache in two ways. The first is just to prefix your
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109 compile commands with "ccache". For example, you could change the
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110 "CC=gcc" line in your Makefile to be "CC=ccache gcc".<p>
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111
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112 Alternatively, you can create symbolic links from your compilers name
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113 to ccache. This allows you to use ccache without any changes to your
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114 build system.
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115
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116 <h2>Download</h2>
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117
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118 You can download the latest release from the <a
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119 href="http://ccache.samba.org/ftp/ccache/">download directory</a>.<p>
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120
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121 For the bleeding edge, you can fetch ccache via CVS or
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122 rsync. To fetch via cvs use the following command:
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123
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124 <pre>
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125 cvs -d :pserver:cvs@pserver.samba.org:/cvsroot co ccache
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126 </pre>
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127
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128 To fetch via rsync use this command:
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129
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130 <pre>
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131 rsync -Pavz samba.org::ftp/unpacked/ccache .
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132 </pre>
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133
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134 <h2>Related projects</h2>
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135
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136 Here are some related programs you may find interesting
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137
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138 <ul>
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139 <li> <a href="http://distcc.samba.org/">distcc</a> - a distributed compilation system
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140 <li> <a href="http://cachecc1.sourceforge.net/">cachecc1</a> - a gcc specific cache
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141 <li> <a href="http://sourceforge.net/projects/gocache/">gocache</a> - a cross platform compiler cache
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142 </ul>
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143 <p>
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144
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145 <h2>Mailing list</h2>
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146
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147 <p>A <a href="http://lists.samba.org/mailman/listinfo/ccache/">mailing
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148 list</a> is available for discussion of ccache.
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149
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150
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151 <hr>
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152 <tiny>
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153 <a href="http://samba.org/~tridge/">Andrew Tridgell</a><br>
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154 <a href="mailto:bugs@ccache.samba.org">bugs@ccache.samba.org</a>
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155 </tiny>
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156
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157 </BODY>
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158 </HTML>
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