HTML source code, style-sheets, scripts, and images for deployment on mingw.osdn.io
| Révision | fea64b5ac1f37c04204fde23ab23d930d33ce04f (tree) |
|---|---|
| l'heure | 2021-12-18 04:27:53 |
| Auteur |  Keith Marshall <keith@user...> |
| Commiter | Keith Marshall |
Publish FAQ note on reducing size of executables.
* exesize.html: New file.
exesize.html (diff)| @@ -0,0 +1,200 @@ | ||
| 1 | +<!DOCTYPE HTML><!-- | |
| 2 | + * | |
| 3 | + * exesize.html | |
| 4 | + * | |
| 5 | + * HOWTO avoid production of excessively large executable files. | |
| 6 | + * | |
| 7 | + * | |
| 8 | + * $Id$ | |
| 9 | + * | |
| 10 | + * Written by Keith Marshall <keith@users.osdn.me> | |
| 11 | + * Copyright (C) 2008, 2021, MinGW.OSDN Project | |
| 12 | + * | |
| 13 | + * | |
| 14 | + * Redistribution and use in source and 'compiled' forms (SGML, HTML, | |
| 15 | + * PDF, PostScript, RTF, etc) with or without modification, are permitted | |
| 16 | + * provided that the following conditions are met: | |
| 17 | + * | |
| 18 | + * 1. Redistributions of source code must retain the above copyright | |
| 19 | + * notice, this list of conditions and the following disclaimer as | |
| 20 | + * the first lines of this file, unmodified. | |
| 21 | + * | |
| 22 | + * 2. Redistributions in compiled form (transformed to other DTDs, | |
| 23 | + * converted to PDF, PostScript, RTF and other formats) must | |
| 24 | + * reproduce the above copyright notice, this list of conditions | |
| 25 | + * and the following disclaimer in the documentation and/or other | |
| 26 | + * materials provided with the distribution. | |
| 27 | + * | |
| 28 | + * THIS DOCUMENTATION IS PROVIDED BY THE MINGW.OSDN PROJECT "AS IS" | |
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| 42 | + * Note: this page assumes browser support for the following numeric | |
| 43 | + * HTML entity codes: | |
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| 51 | + * | |
| 52 | +--> | |
| 53 | +<script class="masthead"> | |
| 54 | +/* Script fragment, to assign titles specific to this page; this is | |
| 55 | + * encapsulated within the "masthead", where such titles are displayed, | |
| 56 | + * to ensure that whatever page content may follow will be correctly | |
| 57 | + * positioned, relative to the masthead content. | |
| 58 | + */ | |
| 59 | + set_page("title", "MinGW Compiler Suite User Guide"); | |
| 60 | + set_page("subtitle", "HOWTO Reduce the Size of MinGW Executable Files"); | |
| 61 | +</script><!-- masthead --> | |
| 62 | +<div class="masthead" style="display: none"> | |
| 63 | +<p class="byline">Posted: 21-Oct-2008, by mingwadmin; Last Update: 22-Nov-2021</p> | |
| 64 | +</div><!-- masthead --> | |
| 65 | +<div class="overlapped" id="introduction"> | |
| 66 | +<h3>Introduction</h3> | |
| 67 | +<p>There are a number of reasons why object files, | |
| 68 | +executable files, | |
| 69 | +and libraries may be larger than expected; | |
| 70 | +principal among these are: | |
| 71 | +</p> | |
| 72 | +<ul> | |
| 73 | + <li>Overheads due to inclusion of debugging information;</li> | |
| 74 | + <li>C++ exception handling and run-time type information overheads;</li> | |
| 75 | + <li>C++ template class, | |
| 76 | + standard template library, | |
| 77 | + and standard C++ library overheads. | |
| 78 | + </li> | |
| 79 | +</ul> | |
| 80 | +<p>Below, | |
| 81 | +we discuss techniques for reducing the impact of these overheads, | |
| 82 | +and ultimately, | |
| 83 | +a technique for compressing executable files, | |
| 84 | +in order to minimize file size. | |
| 85 | +</p> | |
| 86 | +</div><!-- introduction --> | |
| 87 | + | |
| 88 | +<div class="overlapped" id="debug-info"> | |
| 89 | +<h3>Avoiding Inclusion of Debugging Information</h3> | |
| 90 | +<p>Perhaps, | |
| 91 | +the most common reason for executables being larger than expected, | |
| 92 | +is that they include <em>debugging information</em> ; | |
| 93 | +(this is added to the object modules, | |
| 94 | +when source files are compiled with GCC’s | |
| 95 | +“<code>-g</code>” option). | |
| 96 | +Even when your own source files are compiled | |
| 97 | +<em>without</em>  the “<code>-g</code>” option, | |
| 98 | +libraries which are linked into your executable may have been compiled with it; | |
| 99 | +(this may be the case, | |
| 100 | +even for the system libraries which are distributed with MinGW). | |
| 101 | +</p> | |
| 102 | +<p>To exclude debugging information from your executable, | |
| 103 | +simply use the “<code>strip</code>” command to remove it: | |
| 104 | +</p> | |
| 105 | +<pre class="box-out vt"> | |
| 106 | +C:\project> <kbd>strip example.exe</kbd> | |
| 107 | +</pre> | |
| 108 | +<p>Alternatively, | |
| 109 | +use GCC’s “<code>-s</code>” option when linking: | |
| 110 | +</p> | |
| 111 | +<pre class="box-out vt"> | |
| 112 | +C:\project> <kbd>gcc -s example.o -o example.exe</kbd> | |
| 113 | +</pre> | |
| 114 | +</div><!-- debug-info --> | |
| 115 | + | |
| 116 | +<div class="overlapped" id="rtti"> | |
| 117 | +<h3>Reducing C++ Exception Handling and Run‑Time Type Information Overheads</h3> | |
| 118 | +<p>By default, | |
| 119 | +when compiling C++ code, | |
| 120 | +GCC will compile in support for handling of C++ exceptions, | |
| 121 | +and for interpretation of run‑time type information (RTTI). | |
| 122 | +</p> | |
| 123 | +<p>If your application does not use either of these, | |
| 124 | +then you may choose to eliminate the overhead incurred by inclusion | |
| 125 | +of the supporting infrastructure code, | |
| 126 | +by compiling and linking with GCC’s | |
| 127 | +“<code>-fno‑exceptions</code>”, | |
| 128 | +and “<code>-fno‑rtti</code>” options, | |
| 129 | +to eliminate the C++ exception handling, | |
| 130 | +and RTTI interpretation overheads, | |
| 131 | +respectively. | |
| 132 | +</p> | |
| 133 | +</div><!-- rtti --> | |
| 134 | + | |
| 135 | +<div class="overlapped" id="stl"> | |
| 136 | +<h3>Understanding the Effect of C++ Template Classes and the C++ Standard Library</h3> | |
| 137 | +<p>When you use C++ template classes, | |
| 138 | +either defined by yourself, | |
| 139 | +or imported from the C++ Standard Template Library (STL), | |
| 140 | +the compiler generates code separately for each instantiation | |
| 141 | +(e.g. <code>vector<int></code> and <code>vector<string></code>), | |
| 142 | +so the total code size can increase significantly. | |
| 143 | +Other elements of the standard C++ library, | |
| 144 | +such as <code>iostreams</code> classes, | |
| 145 | +exception handling classes, | |
| 146 | +and classes such as <code>std::string</code> introduce further overheads, | |
| 147 | +which may seem large in comparison to the size of small applications, | |
| 148 | +(such as “<code>Hello World</code>” type programs). | |
| 149 | +</p> | |
| 150 | +<p>In practice, | |
| 151 | +these overheads are unavoidable; | |
| 152 | +however, | |
| 153 | +they are generally of constant size, | |
| 154 | +and thus, | |
| 155 | +will normally not be significant in comparison to the size | |
| 156 | +of more realistic (typically larger) C++ application programs. | |
| 157 | +</p> | |
| 158 | +</div><!-- stl --> | |
| 159 | + | |
| 160 | +<div class="overlapped" id="upx"> | |
| 161 | +<h3>Using UPX to Compress Executable Files</h3> | |
| 162 | +<p><a rel="noopener noreferrer" target="_blank" | |
| 163 | + href="https://upx.github.io/">UPX (the Ultimate Packer for eXecutables) | |
| 164 | +</a>is a tool which, | |
| 165 | +notwithstanding the avoidance of undesirable code generator overheads, | |
| 166 | +as described above, | |
| 167 | +compresses executable files to achieve further reduction of file size. | |
| 168 | +It works for the executable file formats of several operating systems, | |
| 169 | +including 32‑bit MS‑Windows, | |
| 170 | +and is free for use with <em>all</em>  applications, | |
| 171 | +(even those which are distributed commercially); | |
| 172 | +it uses an efficient compression algorithm, | |
| 173 | +producing compressed files which remain executable, | |
| 174 | +and are rapidly decompressed <em>in‑place</em>,  | |
| 175 | +when invoked. | |
| 176 | +</p> | |
| 177 | +<p>For most effective size reduction, | |
| 178 | +UPX may deployed using <em>one</em>  of the following invocations, | |
| 179 | +(acting on the original <em>uncompressed</em>  | |
| 180 | +<code>example.exe</code>): | |
| 181 | +</p> | |
| 182 | +<pre class="box-out vt"> | |
| 183 | +C:\project> <kbd>upx --brute example.exe</kbd> | |
| 184 | +C:\project> <kbd>upx --ultra-brute example.exe</kbd> | |
| 185 | +C:\project> <kbd>upx --best example.exe</kbd> | |
| 186 | +</pre> | |
| 187 | +<p>to compress <code>example.exe</code> <em>in‑place</em>.  | |
| 188 | +(Do note that, | |
| 189 | +whereas the in‑place <em>decompression</em>  process | |
| 190 | +can be performed quite rapidly, | |
| 191 | +the <em>compression</em>  may require a considerably longer time; | |
| 192 | +this is not generally a problem, | |
| 193 | +since compression must be performed only once, | |
| 194 | +for each newly generated executable file, | |
| 195 | +whereas the relatively much quicker decompression must be repeated | |
| 196 | +every time such a compressed executable file is run). | |
| 197 | +</p> | |
| 198 | +</div><!-- upx --> | |
| 199 | + | |
| 200 | +<!-- $RCSfile$: end of file --> |
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