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1 \input texinfo @c -*-texinfo-*-
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2
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3 @c %**start of header
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4 @setfilename ../info/emodules.info
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5 @settitle Extending Emacs using C Modules
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6 @direntry
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7 * Emodules: (emodules). XEmacs dynamically loadable module support.
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8 @end direntry
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9 @c footnotestyle separate
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10 @c paragraphindent 2
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11 @c %**end of header
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12
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13 @c
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14 @c Use some macros so that we can format for either XEmacs
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15 @c or (shudder) GNU Emacs.
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16 @c
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17
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18 @ifset XEMACS
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19 @set emacs XEmacs
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20 @clear EMACS
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21 @set HAVE-EMACS
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22 @end ifset
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23
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24 @ifset EMACS
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25 @set emacs Emacs
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26 @clear XEMACS
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27 @set HAVE-EMACS
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28 @end ifset
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29
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30 @ifclear HAVE-EMACS
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31 @set XEMACS
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32 @set emacs XEmacs
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33 @end ifclear
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34
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35 @ifinfo
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36 This file documents the module loading technology of @value{emacs}.
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37
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38 Copyright @copyright{} 1998 J. Kean Johnston.
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39
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40 Permission is granted to make and distribute verbatim copies of this
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41 manual provided the copyright notice and this permission notice are
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42 preserved on all copies.
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43
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44 @ignore
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45 Permission is granted to process this file through TeX and print the
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46 results, provided the printed document carries copying permission notice
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47 identical to this one except for the removal of this paragraph (this
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48 paragraph not being relevant to the printed manual).
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49
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50 @end ignore
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51 Permission is granted to copy and distribute modified versions of this
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52 manual under the conditions for verbatim copying, provided that the
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53 entire resulting derived work is distributed under the terms of a
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54 permission notice identical to this one.
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55
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56 Permission is granted to copy and distribute translations of this manual
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57 into another language, under the above conditions for modified versions,
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58 except that this permission notice may be stated in a translation
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59 approved by the Foundation.
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60
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61 Permission is granted to copy and distribute modified versions of this
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62 manual under the conditions for verbatim copying, provided also that the
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63 section entitled ``GNU General Public License'' is included exactly as
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64 in the original, and provided that the entire resulting derived work is
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65 distributed under the terms of a permission notice identical to this
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66 one.
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67
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68 Permission is granted to copy and distribute translations of this manual
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69 into another language, under the above conditions for modified versions,
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70 except that the section entitled ``GNU General Public License'' may be
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71 included in a translation approved by the Free Software Foundation
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72 instead of in the original English.
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73 @end ifinfo
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74
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75 @c Combine indices.
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76 @syncodeindex fn cp
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77 @syncodeindex vr cp
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78 @syncodeindex ky cp
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79 @syncodeindex pg cp
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80 @syncodeindex tp cp
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81
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82 @setchapternewpage odd
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83 @finalout
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84
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85 @titlepage
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86 @title Extending @value{emacs} using C and C++
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87 @subtitle Version 1.0, September 1998
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88
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89 @author J. Kean Johnston
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90 @page
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91 @vskip 0pt plus 1fill
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92
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93 @noindent
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94 Copyright @copyright{} 1998 J. Kean Johnston. @*
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95
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96 @sp 2
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97 Version 1.0 @*
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98 September, 1998.@*
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99
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100 Permission is granted to make and distribute verbatim copies of this
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101 manual provided the copyright notice and this permission notice are
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102 preserved on all copies.
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103
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104 Permission is granted to copy and distribute modified versions of this
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105 manual under the conditions for verbatim copying, provided also that the
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106 section entitled ``GNU General Public License'' is included
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107 exactly as in the original, and provided that the entire resulting
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108 derived work is distributed under the terms of a permission notice
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109 identical to this one.
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110
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111 Permission is granted to copy and distribute translations of this manual
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112 into another language, under the above conditions for modified versions,
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113 except that the section entitled ``GNU General Public License'' may be
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114 included in a translation approved by the Free Software Foundation
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115 instead of in the original English.
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116 @end titlepage
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117 @page
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118
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119 @ifinfo
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120 @node Top, Introduction, (dir), (dir)
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121 This Info file contains v1.0 of the @value{emacs} dynamically loadable
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122 module support documentation.
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123 @menu
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124 * Introduction:: Introducing Emacs Modules
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442
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125 * Anatomy of a Module:: Basic module layout and technology
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126 * Using ellcc:: How to use the module compiler
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127 * Defining Functions:: Creating new Lisp primitives
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128 * Defining Variables:: Creating new Lisp variables
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129 * Index:: Concept Index
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130
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131 --- The Detailed Node Listing ---
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132
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133 Anatomy of a Module
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134
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135 * Required Header File:: Always include <emodules.h>
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136 * Required Functions:: Functions you must always provide
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137 * Required Variables:: Variables whose values you must provide
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138 * Loading other Modules:: How to load dependent modules
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139
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140 Using @code{ellcc}
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141
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142 * Compile Mode:: Compiling modules using ellcc
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143 * Initialization Mode:: Generating documentation and variables
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144 * Link Mode:: Creating the final loadable module
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145 * Other ellcc options:: Other useful options
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146 * Environment Variables:: How to control ellcc
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147
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148 Defining Functions
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149
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150 * Using DEFUN:: Using the DEFUN macro to define functions
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151 * Declaring Functions:: Declaring functions to the Lisp reader
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152 @end menu
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153
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154 @end ifinfo
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155
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442
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156 @node Introduction, Anatomy of a Module, Top, Top
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157 @chapter Introduction
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158
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159 @value{emacs} is a powerful, extensible editor. The traditional way of
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160 extending the functionality of @value{emacs} is to use its built-in Lisp
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161 language (called Emacs Lisp, or Elisp for short). However, while Elisp
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162 is a full programming language and capable of extending @value{emacs} in more
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163 ways than you can imagine, it does have its short-comings.
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164
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165 Firstly, Elisp is an interpreted language, and this has serious speed
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166 implications. Like all other interpreted languages (like Java), Elisp
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167 is often suitable only for certain types of application or extension.
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168 So although Elisp is a general purpose language, and very high level,
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169 there are times when it is desirable to descend to a lower level compiled
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170 language for speed purposes.
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171
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172 Secondly, Elisp (or Lisp in general) is not a very common language any
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173 more, except for certain circles in the computer industry. C is a far
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174 more commonly known language, and because it is compiled, more suited to
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175 a wider range of applications, especially those that require low level
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176 access to a system or need to be as quick as possible.
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177
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178 @cindex Emacs Modules
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179 @cindex DLL
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180 @cindex DSO
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181 @cindex shared object
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182 This manual describes a new way of extending @value{emacs}, by using
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183 dynamically loadable modules (also known as dynamically loadable
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184 libraries (DLLs), dynamic shared objects (DSOs) or just simply shared
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185 objects), which can be written in C or C++ and loaded into @value{emacs}
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186 at any time. I sometimes refer to this technology as @dfn{CEmacs},
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187 which is short for @dfn{C Extensible Emacs}.
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188
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189 @value{emacs} modules are configured into and installed with @value{emacs} by
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190 default on all systems that support loading of shared objects. From a
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191 users perspective, the internals of @value{emacs} modules are irrelevant.
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192 All a user will ever need to know about shared objects is the name of
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193 the shared object when they want to load a given module. From a
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194 developers perspective though, a lot more is provided.
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195
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196 @itemize @bullet
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197 @item
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198 @pindex ellcc
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199 @cindex compiler
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200 @cindex linker
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201 Of primary interest is the @code{ellcc} program. This program is
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202 created during compile time, and is intended to abstract compiler
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203 specific characteristics from the developer. This program is called to
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204 compile and link all objects that will make up the final shared object,
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205 and accepts all common C compiler flags. @code{ellcc} also sets up the
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206 correct environment for compiling modules by enabling any special
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207 compiler modes (such as PIC mode), setting the correct include paths for
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208 the location of @value{emacs} internal header files etc. The program will also
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209 invoke the linker correctly to created the final shared object which is
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210 loaded into @value{emacs}.
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211
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212 @item
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213 @cindex header files
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214 CEmacs also makes all of the relevant @value{emacs} internal header files
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215 available for module authors to use. This is often required to get data
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216 structure definitions and external variable declarations. The header
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217 files installed include the module specific header file
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218 @file{emodules.h}. Due to the nature of dynamic modules, most of the
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219 internals of @value{emacs} are exposed.
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220 @xref{Top,,,internals,@value{emacs} Internals Manual}, for a
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221 more complete discussion on how to extend and understand @value{emacs}. All of
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222 the rules for C modules are discussed there.
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223
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224 @item
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225 @cindex samples
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226 Part of the @value{emacs} distribution is a set of sample modules. These are
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227 not installed when @value{emacs} is, but remain in the @value{emacs} source tree.
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228 These modules live in the directory @file{modules}, which is a
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229 sub-directory of the main @value{emacs} source code directory. Please look at
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230 the samples carefully, and maybe even use them as a basis for making
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231 your own modules. Most of the concepts required for writing extension
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232 modules are covered in the samples.
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233
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234 @item
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235 @cindex documentation
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236 @cindex help
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237 Last, but not least is this manual. This can be viewed from within
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238 @value{emacs}, and it can be printed out as well. It is the intention of this
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239 document that it will describe everything you need to know about
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240 extending @value{emacs} in C. If you do not find this to be the case, please
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241 contact the author(s).
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242 @end itemize
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243
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244 The rest of this document will discuss the actual mechanics of
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245 @value{emacs} modules and work through several of the samples. Please be
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246 sure that you have read the @value{emacs} Internals Manual and understand
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247 everything in it. The concepts there apply to all modules. This
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248 document may have some overlap, but it is the internals manual which
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249 should be considered the final authority. It will also help a great
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250 deal to look at the actual @value{emacs} source code to see how things are
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251 done.
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252
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442
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253 @node Anatomy of a Module, Using ellcc, Introduction, Top
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254 @chapter Anatomy of a Module
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255 @cindex anatomy
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428
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256 @cindex module skeleton
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257 @cindex skeleton, module
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258 @cindex module format
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259 @cindex format, module
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260
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442
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261 Each dynamically loadable @value{emacs} extension (hereafter referred to as a
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262 module) has a certain compulsory format, and must contain several
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263 pieces of information and several mandatory functions. This chapter
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428
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264 describes the basic layout of a module, and provides a very simple
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265 sample. The source for this sample can be found in the file
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266 @file{modules/simple/sample.c} in the main @value{emacs} source code tree.
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267
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268 @menu
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269 * Required Header File:: Always include <emodules.h>
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270 * Required Functions:: Functions you must always provide
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271 * Required Variables:: Variables whose values you must provide
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442
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272 * Loading other Modules:: How to load dependent modules
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273 @end menu
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274
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442
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275 @node Required Header File, Required Functions, Anatomy of a Module, Anatomy of a Module
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428
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276 @section Required Header File
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277 @cindex required header
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278 @cindex include files
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279
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280 @cindex emodules.h
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281 @cindex config.h
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282 Every module must include the file @file{<emodules.h>}. This
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442
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283 will include several other @value{emacs} internal header files, and will set up
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428
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284 certain vital macros. One of the most important files included by
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285 @file{emodules.h} is the generated @file{config.h} file, which contains
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286 all of the required system abstraction macros and definitions. Most
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287 modules will probably require some pre-processor conditionals based on
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288 constants defined in @file{config.h}. Please read that file to
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289 familiarize yourself with the macros defined there.
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290
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442
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291 Depending on exactly what your module will be doing, you will probably
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428
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292 need to include one or more of the @value{emacs} internal header files. When
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293 you @code{#include <emodules.h>}, you will get a few of the most important
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428
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294 @value{emacs} header files included automatically for you. The files included
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295 are:
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296
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297 @table @file
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298 @item lisp.h
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299 This file contains most of the macros required for declaring Lisp object
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300 types, macros for accessing Lisp objects, and global variable
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301 declarations.
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302
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303 @item sysdep.h
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442
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304 All system dependent declarations and abstraction macros live here. You
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428
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305 should never call low level system functions directly. Rather, you
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306 should use the abstraction macros provided in this header file.
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307
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308 @item window.h
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309 This header file defines the window structures and Lisp types, and
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310 provides functions and macros for manipulating multiple @value{emacs} windows.
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311
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312 @item buffer.h
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313 All macros and function declarations for manipulating internal and user
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314 visible buffers appear in this file.
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315
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316 @item insdel.h
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317 This header provides the information required for performing text
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318 insertion and deletion.
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319
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320 @item frame.h
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321 Provides the required structure, macro and function definitions for
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322 manipulating @value{emacs} frames.
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323 @end table
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324
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442
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325 @node Required Functions, Required Variables, Required Header File, Anatomy of a Module
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428
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326 @section Required Functions
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327 @cindex initialization
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328 @cindex functions, required
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329 @cindex required functions
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330
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331 Every module requires several initialization functions. It is the
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442
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332 responsibility of these functions to load in any dependent modules, and to
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333 declare all variables and functions which are to be made visible to the
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428
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334 @value{emacs} Lisp reader. Each of these functions performs a very specific
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335 task, and they are executed in the correct order by @value{emacs}. All of
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336 these functions are @code{void} functions which take no arguments.
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337 Here, briefly, are the required module functions. Note that the actual
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338 function names do not end with the string @code{_module}, but rather
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339 they end with the abbreviated module name by which the module is known.
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340 More on the module name and its importance later. Just bear in mind
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341 that the text @code{_module} in the functions below is simply a
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342 place-holder, not an actual function name.
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343
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344 @table @code
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345 @item syms_of_module
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346 @findex syms_of_module
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442
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347 This required function is responsible for introducing to the Lisp reader
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428
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348 all functions that you have defined in your module using
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349 @code{DEFUN()}. Note that @emph{only} functions are declared here, using
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350 the @code{DEFSUBR()} macro. No variables are declared.
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351
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352 @item vars_of_module
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353 @findex vars_of_module
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354 This required function contains calls to macros such as
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355 @code{DEFVAR_LISP()}, @code{DEFVAR_BOOL()} etc, and its purpose is to
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356 declare and initialize all and any variables that your module defines.
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357 They syntax for declaring variables is identical to the syntax used for
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450
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358 all internal @value{emacs} source code. If the module is intended to be
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359 usable statically linked into XEmacs, the actions of this function are
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360 severely restricted. @xref{General Coding Rules,,,internals,
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361 @value{emacs} Internals Manual}. Also see the comments in
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362 @file{src/emacs.c} (@code{main_1}). Modules which perform
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363 initializations not permitted by these rules will probably work, but
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364 dual-use (dynamic loading and static linking) modules will require very
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365 careful, and possibly fragile, coding.
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428
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366
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367 @item modules_of_module
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368 @findex modules_of_module
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369 This optional function should be used to load in any modules which your
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442
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370 module depends on. The @value{emacs} module loading code makes sure that the
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428
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371 same module is not loaded twice, so several modules can safely call the
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372 module load function for the same module. Only one copy of each module
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373 (at a given version) will ever be loaded.
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374
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375 @item docs_of_module
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376 @findex docs_of_module
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377 This is a required function, but not one which you need ever write.
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378 This function is created automatically by @code{ellcc} when the module
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379 initialization code is produced. It is required to document all
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380 functions and variables declared in your module.
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381 @end table
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382
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442
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383 @node Required Variables, Loading other Modules, Required Functions, Anatomy of a Module
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428
|
384 @section Required Variables
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385 @cindex initialization
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386 @cindex variables, required
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387 @cindex required variables
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388
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389 Not only does a module need to declare the initialization functions
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390 mentioned above, it is also required to provide certain variables which
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442
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391 the module loading code searches for in order to determine the viability
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428
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392 of a module. You are @emph{not} required to provide these variables in
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393 your source files. They are automatically set up in the module
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394 initialization file by the @code{ellcc} compiler. These variables are
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395 discussed here simply for the sake of completeness.
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396
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397 @table @code
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398 @item emodules_compiler
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399 This is a variable of type @code{long}, and is used to indicate the
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400 version of the @value{emacs} loading technology that was used to produce the
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401 module being loaded. This version number is completely unrelated to
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402 the @value{emacs} version number, as a given module may quite well work
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442
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403 regardless of the version of @value{emacs} that was installed at the time the
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428
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404 module was created.
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405
|
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406 The @value{emacs} modules version is used to differentiate between major
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407 changes in the module loading technology, not versions of @value{emacs}.
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408
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409 @item emodules_name
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410 This is a short (typically 10 characters or less) name for the module,
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411 and it is used as a suffix for all of the required functions. This is
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442
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412 also the name by which the module is recognized when loading dependent
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428
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413 modules. The name does not necessarily have to be the same as the
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414 physical file name, although keeping the two names in sync is a pretty
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442
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415 good idea. The name must not be empty, and it must be a valid part of a
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416 C function name. The value of this variable is appended to the function
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428
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417 names @code{syms_of_}, @code{vars_of_}, @code{modules_of_} and
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418 @code{docs_of_} to form the actual function names that the module
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419 loading code looks for when loading a module.
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420
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421 This variable is set by the @code{--mod-name} argument to @code{ellcc}.
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422
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423 @item emodules_version
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424 This string variable is used to load specific versions of a module.
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425 Rarely will two or more versions of a module be left lying around, but
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426 just in case this does happen, this variable can be used to control
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427 exactly which module should be loaded. See the Lisp function
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428 @code{load-module} for more details. This variable is set by the
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429 @code{--mod-version} argument to @code{ellcc}.
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430
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431 @item emodules_title
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432 This is a string which describes the module, and can contain spaces or
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433 other special characters. It is used solely for descriptive purposes,
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434 and does not affect the loading of the module. The value is set by the
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435 @code{--mod-title} argument to @code{ellcc}.
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436 @end table
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437
|
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442
|
438 @node Loading other Modules, , Required Variables, Anatomy of a Module
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428
|
439 @section Loading other Modules
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442
|
440 @cindex dependencies
|
|
428
|
441 @findex modules_of_module
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442 @findex emodules_load
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443
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444 During the loading of a module, it is the responsibility of the function
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445 @code{modules_of_module} to load in any modules which the current module
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446 depends on. If the module is stand-alone, and does not depend on other
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447 modules, then this function can be left empty or even undeclared.
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442
|
448 However, if it does have dependencies, it must call
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428
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449 @code{emodules_load}:
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450
|
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451 @example
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452 @cartouche
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442
|
453 int emodules_load (const char *module,
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454 const char *modname,
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455 const char *modver)
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428
|
456 @end cartouche
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|
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457 @end example
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458
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442
|
459 The first argument @var{module} is the name of the actual shared object
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428
|
460 or DLL. You can omit the @file{.so}, @file{.ell} or @file{.dll}
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|
461 extension of you wish. If you do not specify an absolute path name,
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|
462 then the same rules as apply to loading Lisp modules are applied when
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463 searching for the module. If the module cannot be found in any of the
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464 standard places, and an absolute path name was not specified,
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442
|
465 @code{emodules_load} will signal an error and loading of the module
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428
|
466 will stop.
|
|
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467
|
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468 The second argument (@var{modname}) is the module name to load, and
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|
469 must match the contents of the variable @var{emodule_name} in the
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442
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470 module to be loaded. A mis-match will cause the module load to fail. If
|
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428
|
471 this parameter is @code{NULL} or empty, then no checks are performed
|
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472 against the target module's @var{emodule_name} variable.
|
|
|
473
|
|
|
474 The last argument, @var{modver}, is the desired version of the module
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|
|
475 to load, and is compared to the target module's
|
|
|
476 @var{emodule_version} value. If this parameter is not @code{NULL}
|
|
|
477 or empty, and the match fails, then the load of the module will fail.
|
|
|
478
|
|
|
479 @code{emodules_load} can be called recursively. If, at any point
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442
|
480 during the loading of modules a failure is encountered, then all modules
|
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428
|
481 that were loaded since the top level call to @code{emodules_load}
|
|
|
482 will be unloaded. This means that if any child modules fail to load,
|
|
|
483 then their parents will also fail to load. This does not include
|
|
|
484 previous successful calls to @code{emodules_load} at the top level.
|
|
|
485
|
|
880
|
486 @strong{Warning:} Modules are @emph{not} loaded with the
|
|
|
487 @code{RTLD_GLOBAL} flag. The practical upshot is that individual
|
|
|
488 modules do not have access to each other's C symbols. One module cannot
|
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|
489 make a C function call to a function defined in another module, nor can
|
|
|
490 it read or set a C variable in another module. All interaction between
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|
|
491 modules must, therefore, take place at the Lisp level. This is by
|
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|
492 design. Other projects have attempted to use @code{RTLD_GLOBAL}, only
|
|
|
493 to find that spurious symbol name clashes were the result. Helper
|
|
|
494 functions often have simple names, increasing the probability of such a
|
|
|
495 clash. If you really need to share symbols between modules, create a
|
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|
496 shared library containing those symbols, and link your modules with
|
|
|
497 that library. Otherwise, interactions between modules must take place
|
|
|
498 via Lisp function calls and Lisp variables accesses.
|
|
|
499
|
|
442
|
500 @node Using ellcc, Defining Functions, Anatomy of a Module, Top
|
|
428
|
501 @chapter Using @code{ellcc}
|
|
|
502 @cindex @code{ellcc}
|
|
|
503 @cindex module compiler
|
|
|
504
|
|
|
505 Before discussing the anatomy of a module in greater detail, you should
|
|
|
506 be aware of the steps required in order to correctly compile and link a
|
|
|
507 module for use within @value{emacs}. There is little difference between
|
|
|
508 compiling normal C code and compiling a module. In fact, all that
|
|
|
509 changes is the command used to compile the module, and a few extra
|
|
|
510 arguments to the compiler.
|
|
|
511
|
|
|
512 @value{emacs} now ships with a new user utility, called @code{ellcc}. This
|
|
|
513 is the @dfn{Emacs Loadable Library C Compiler}. This is a wrapper
|
|
|
514 program that will invoke the real C compiler with the correct arguments
|
|
|
515 to compile and link your module. With the exception of a few command
|
|
|
516 line options, this program can be considered a replacement for your C
|
|
|
517 compiler. It accepts all of the same flags and arguments that your C
|
|
|
518 compiler does, so in many cases you can simply set the @code{make}
|
|
|
519 variable @code{CC} to @code{ellcc} and your code will be compiled as
|
|
|
520 an Emacs module rather than a static C object.
|
|
|
521
|
|
|
522 @code{ellcc} has three distinct modes of operation. It can be run in
|
|
442
|
523 compile, link or initialization mode. These modes are discussed in more
|
|
428
|
524 detail below. If you want @code{ellcc} to show the commands it is
|
|
|
525 executing, you can specify the option @code{--mode=verbose} to
|
|
|
526 @code{ellcc}. Specifying this option twice will enable certain extra
|
|
|
527 debugging messages to be displayed on the standard output.
|
|
|
528
|
|
|
529 @menu
|
|
|
530 * Compile Mode:: Compiling modules using ellcc
|
|
|
531 * Initialization Mode:: Generating documentation and variables
|
|
|
532 * Link Mode:: Creating the final loadable module
|
|
|
533 * Other ellcc options:: Other useful options
|
|
|
534 * Environment Variables:: How to control ellcc
|
|
|
535 @end menu
|
|
|
536
|
|
|
537 @node Compile Mode, Initialization Mode, Using ellcc, Using ellcc
|
|
|
538 @section Compile Mode
|
|
|
539 @cindex compiling
|
|
|
540
|
|
|
541 By default, @code{ellcc} is in @dfn{compile} mode. This means that it
|
|
442
|
542 assumes that all of the command line arguments are C compiler arguments,
|
|
428
|
543 and that you want to compile the specified source file or files. You
|
|
|
544 can force compile mode by specifying the @code{--mode=compile} argument
|
|
|
545 to @code{ellcc}.
|
|
|
546
|
|
|
547 In this mode, @code{ellcc} is simply a front-end to the same C compiler
|
|
|
548 that was used to create the @value{emacs} binary itself. All @code{ellcc}
|
|
|
549 does in this mode is insert a few extra command line arguments before
|
|
|
550 the arguments you specify to @code{ellcc} itself. @code{ellcc} will
|
|
|
551 then invoke the C compiler to compile your module, and will return the
|
|
|
552 same exit codes and messages that your C compiler does.
|
|
|
553
|
|
|
554 By far the easiest way to compile modules is to construct a
|
|
442
|
555 @file{Makefile} as you would for a normal program, and simply insert, at
|
|
428
|
556 some appropriate place something similar to:
|
|
|
557
|
|
|
558 @example
|
|
|
559 @cartouche
|
|
|
560 CC=ellcc --mode=compile
|
|
|
561
|
|
|
562 .c.o:
|
|
|
563 $(CC) $(CFLAGS) -c $<
|
|
|
564 @end cartouche
|
|
|
565 @end example
|
|
|
566
|
|
|
567 After this, all you need to do is provide simple @code{make} rules for
|
|
|
568 compiling your module source files. Since modules are most useful when
|
|
|
569 they are small and self-contained, most modules will have a single
|
|
|
570 source file, aside from the module specific initialization file (see
|
|
|
571 below for details).
|
|
|
572
|
|
|
573 @node Initialization Mode, Link Mode, Compile Mode, Using ellcc
|
|
|
574 @section Initialization Mode
|
|
|
575 @cindex initialization
|
|
|
576 @cindex documentation
|
|
|
577
|
|
|
578 @value{emacs} uses a rather bizarre way of documenting variables and
|
|
|
579 functions. Rather than have the documentation for compiled functions
|
|
|
580 and variables passed as static strings in the source code, the
|
|
|
581 documentation is included as a C comment. A special program, called
|
|
|
582 @file{make-docfile}, is used to scan the source code files and extract
|
|
442
|
583 the documentation from these comments, producing the @value{emacs} @file{DOC}
|
|
428
|
584 file, which the internal help engine scans when the documentation for a
|
|
|
585 function or variable is requested.
|
|
|
586
|
|
|
587 Due to the internal construction of Lisp objects, subrs and other such
|
|
|
588 things, adding documentation for a compiled function or variable in a
|
|
|
589 compiled module, at any time after @value{emacs} has been @dfn{dumped} is
|
|
442
|
590 somewhat problematic. Fortunately, as a module writer you are insulated
|
|
428
|
591 from the difficulties thanks to your friend @code{ellcc} and some
|
|
|
592 internal trickery in the module loading code. This is all done using
|
|
|
593 the @dfn{initialization} mode of @code{ellcc}.
|
|
|
594
|
|
|
595 The result of running @code{ellcc} in initialization mode is a C source
|
|
|
596 file which you compile with (you guessed it) @code{ellcc} in compile
|
|
|
597 mode. Initialization mode is where you set the module name, version,
|
|
442
|
598 title and gather together all of the documentation strings for the
|
|
|
599 functions and variables in your module. There are several options that
|
|
428
|
600 you are required to pass @code{ellcc} in initialization mode, the first
|
|
|
601 of which is the mode switch itself, @code{--mode=init}.
|
|
|
602
|
|
|
603 Next, you need to specify the name of the C source code file that
|
|
|
604 @code{ellcc} will produce, and you specify this using the
|
|
|
605 @code{--mod-output=FILENAME} argument. @var{FILENAME} is the name of
|
|
|
606 the C source code file that will contain the module variables and
|
|
|
607 @code{docs_of_module} function.
|
|
|
608
|
|
|
609 As discussed previously, each module requires a short @dfn{handle} or
|
|
|
610 module name. This is specified with the @code{--mod-name=NAME} option,
|
|
|
611 where @var{NAME} is the abbreviated module name. This @var{NAME} must
|
|
|
612 consist only of characters that are valid in C function and variable
|
|
|
613 names.
|
|
|
614
|
|
|
615 The module version is specified using @code{--mod-version=VERSION}
|
|
|
616 argument, with @var{VERSION} being any arbitrary version string. This
|
|
|
617 version can be passed as an optional second argument to the Lisp
|
|
|
618 function @code{load-module}, and as the third argument to the internal
|
|
|
619 module loading command @code{emodules_load}. This version string is
|
|
|
620 used to distinguish between different versions of the same module, and
|
|
|
621 to ensure that the module is loaded at a specific version.
|
|
|
622
|
|
|
623 Last, but not least, is the module title. Specified using the
|
|
|
624 @code{--mod-title=TITLE} option, the specified @var{TITLE} is used when
|
|
|
625 the list of loaded modules is displayed. The module title serves no
|
|
|
626 purpose other than to inform the user of the function of the module.
|
|
|
627 This string should be brief, as it has to be formatted to fit the
|
|
|
628 screen.
|
|
|
629
|
|
|
630 Following all of these parameters, you need to provide the list of all
|
|
442
|
631 source code modules that make up your module. These are the files which
|
|
|
632 are scanned by @file{make-docfile}, and provide the information required
|
|
428
|
633 to populate the @code{docs_of_module} function. Below is a sample
|
|
|
634 @file{Makefile} fragment which indicates how all of this is used.
|
|
|
635
|
|
|
636 @example
|
|
|
637 @cartouche
|
|
|
638 CC=ellcc --mode=compile
|
|
|
639 LD=ellcc --mode=link
|
|
|
640 MODINIT=ellcc --mode=init
|
|
|
641 CFLAGS=-O2 -DSOME_STUFF
|
|
|
642
|
|
|
643 .c.o:
|
|
|
644 $(CC) $(CFLAGS) -c $<
|
|
|
645
|
|
|
646 MODNAME=sample
|
|
|
647 MODVER=1.0.0
|
|
|
648 MODTITLE="Small sample module"
|
|
|
649
|
|
|
650 SRCS=modfile1.c modfile2.c modfile3.c
|
|
|
651 OBJS=$(SRCS:.c=.o)
|
|
|
652
|
|
|
653 all: sample.ell
|
|
|
654 clean:
|
|
|
655 rm -f $(OBJS) sample_init.o sample.ell
|
|
|
656
|
|
|
657 install: all
|
|
|
658 mkdir `ellcc --mod-location`/mymods > /dev/null
|
|
|
659 cp sample.ell `ellcc --mod-location`/mymods/sample.ell
|
|
|
660
|
|
|
661 sample.ell: $(OBJS) sample_init.o
|
|
|
662 $(LD) --mod-output=$@ $(OBJS) sample_init.o
|
|
|
663
|
|
|
664 sample_init.o: sample_init.c
|
|
|
665 sample_init.c: $(SRCS)
|
|
|
666 $(MODINIT) --mod-name=$(MODNAME) --mod-version=$(MODVER) \
|
|
|
667 --mod-title=$(MODTITLE) --mod-output=$@ $(SRCS)
|
|
|
668 @end cartouche
|
|
|
669 @end example
|
|
|
670
|
|
|
671 The above @file{Makefile} is, in fact, complete, and would compile the
|
|
|
672 sample module, and optionally install it. The @code{--mod-location}
|
|
|
673 argument to @code{ellcc} will produce, on the standard output, the base
|
|
|
674 location of the @value{emacs} module directory. Each sub-directory of that
|
|
625
|
675 directory is automatically searched for modules when they are loaded with
|
|
|
676 @code{load-module}. An alternative location would be
|
|
|
677 @file{/usr/local/lib/xemacs/site-modules}. That path can change depending
|
|
|
678 on the options the person who compiled @value{emacs} chose, so you can
|
|
|
679 always determine the correct site location using the
|
|
|
680 @code{--mod-site-location} option. This directory is treated the same way
|
|
|
681 as the main module directory. Each sub-directory within it is searched for
|
|
|
682 a given module when the user attempts to load it. The valid extensions that
|
|
|
683 the loader attempts to use are @file{.so}, @file{.ell} and @file{.dll}. You
|
|
|
684 can use any of these extensions, although @file{.ell} is the preferred
|
|
|
685 extension.
|
|
428
|
686
|
|
|
687 @node Link Mode, Other ellcc options, Initialization Mode, Using ellcc
|
|
|
688 @section Link Mode
|
|
|
689 @cindex linking
|
|
|
690
|
|
|
691 Once all of your source code files have been compiled (including the
|
|
442
|
692 generated init file) you need to link them all together to create the
|
|
428
|
693 loadable module. To do this, you invoke @code{ellcc} in link mode, by
|
|
450
|
694 passing the @code{--mode=link} option. You need to specify the final
|
|
442
|
695 output file using the @code{--mod-output=NAME} option, but other than
|
|
428
|
696 that all other arguments are passed on directly to the system compiler
|
|
|
697 or linker, along with any other required arguments to create the
|
|
|
698 loadable module.
|
|
|
699
|
|
|
700 The module has complete access to all symbols that were present in the
|
|
|
701 dumped @value{emacs}, so you do not need to link against libraries that were
|
|
|
702 linked in with the main executable. If your library uses some other
|
|
|
703 extra libraries, you will need to link with those. There is nothing
|
|
|
704 particularly complicated about link mode. All you need to do is make
|
|
|
705 sure you invoke it correctly in the @file{Makefile}. See the sample
|
|
|
706 @file{Makefile} above for an example of a well constructed
|
|
|
707 @file{Makefile} that invoked the linker correctly.
|
|
|
708
|
|
|
709 @node Other ellcc options, Environment Variables, Link Mode, Using ellcc
|
|
|
710 @section Other @code{ellcc} options
|
|
|
711 @cindex paths
|
|
|
712
|
|
|
713 Aside from the three main @code{ellcc} modes described above,
|
|
|
714 @code{ellcc} can accept several other options. These are typically used
|
|
442
|
715 in a @file{Makefile} to determine installation paths. @code{ellcc} also
|
|
428
|
716 allows you to over-ride several of its built-in compiler and linker
|
|
|
717 options using environment variables. Here is the complete list of
|
|
|
718 options that @code{ellcc} accepts.
|
|
|
719
|
|
|
720 @table @code
|
|
|
721 @item --mode=compile
|
|
|
722 Enables compilation mode. Use this to compile source modules.
|
|
|
723
|
|
|
724 @item --mode=link
|
|
|
725 Enabled link edit mode. Use this to create the final module.
|
|
|
726
|
|
|
727 @item --mode=init
|
|
|
728 Used to create the documentation function and to initialize other
|
|
442
|
729 required variables. Produces a C source file that must be compiled with
|
|
428
|
730 @code{ellcc} in compile mode before linking the final module.
|
|
|
731
|
|
|
732 @item --mode=verbose
|
|
|
733 Enables verbose mode. This will show you the commands that are being
|
|
442
|
734 executed, as well as the version number of @code{ellcc}. If you specify
|
|
428
|
735 this option twice, then some extra debugging information is displayed.
|
|
|
736
|
|
|
737 @item --mod-name=NAME
|
|
442
|
738 Sets the short internal module @var{NAME} to the string specified,
|
|
428
|
739 which must consist only of valid C identifiers. Required during
|
|
|
740 initialization mode.
|
|
|
741
|
|
|
742 @item --mod-version=VERSION
|
|
|
743 Sets the internal module @var{VERSION} to the specified string.
|
|
|
744 Required during initialization mode.
|
|
|
745
|
|
|
746 @item --mod-title=TITLE
|
|
|
747 Sets the module descriptive @var{TITLE} to the string specified. This
|
|
|
748 string can contain any printable characters, but should not be too
|
|
|
749 long. It is required during initialization mode.
|
|
|
750
|
|
|
751 @item --mod-output=FILENAME
|
|
|
752 Used to control the output file name. This is used during
|
|
|
753 initialization mode to set the name of the C source file that will be
|
|
|
754 created to @var{FILENAME}. During link mode, it sets the name of the
|
|
|
755 final loadable module to @var{FILENAME}.
|
|
|
756
|
|
|
757 @item --mod-location
|
|
442
|
758 This will print the name of the standard module installation path on the
|
|
428
|
759 standard output and immediately exit @code{ellcc}. Use this option to
|
|
|
760 determine the directory prefix of where you should install your modules.
|
|
|
761
|
|
|
762 @item --mod-site-location
|
|
|
763 This will print the name of the site specific module location and exit.
|
|
|
764
|
|
|
765 @item --mod-archdir
|
|
442
|
766 Prints the name of the root of the architecture-dependent directory that
|
|
|
767 @value{emacs} searches for architecture-dependent files.
|
|
428
|
768
|
|
|
769 @item --mod-config
|
|
442
|
770 Prints the name of the configuration for which @value{emacs} and @code{ellcc}
|
|
428
|
771 were compiled.
|
|
|
772 @end table
|
|
|
773
|
|
|
774 @node Environment Variables, , Other ellcc options, Using ellcc
|
|
|
775 @section Environment Variables
|
|
|
776 @cindex environment variables
|
|
|
777
|
|
|
778 During its normal operation, @code{ellcc} uses the compiler and linker
|
|
|
779 flags that were determined at the time @value{emacs} was configured. In
|
|
442
|
780 certain rare circumstances you may wish to over-ride the flags passed to
|
|
428
|
781 the compiler or linker, and you can do so using environment variables.
|
|
442
|
782 The table below lists all of the environment variables that @code{ellcc}
|
|
|
783 recognizes.
|
|
428
|
784
|
|
|
785 @table @code
|
|
|
786 @item ELLCC
|
|
|
787 @cindex @code{ELLCC}
|
|
|
788 This is used to over-ride the name of the C compiler that is invoked by
|
|
|
789 @code{ellcc}.
|
|
|
790
|
|
|
791 @item ELLLD
|
|
|
792 @cindex @code{ELLLD}
|
|
|
793 Sets the name of the link editor to use to created the final module.
|
|
|
794
|
|
|
795 @item ELLCFLAGS
|
|
|
796 @cindex @code{ELLCFLAGS}
|
|
|
797 Sets the compiler flags passed on when compiling source modules. This
|
|
|
798 only sets the basic C compiler flags. There are certain hard-coded
|
|
|
799 flags that will always be passed.
|
|
|
800
|
|
|
801 @item ELLLDFLAGS
|
|
|
802 @cindex @code{ELLLDFLAGS}
|
|
|
803 Sets the flags passed on to the linker. This does @strong{not} include
|
|
|
804 the flags for enabling PIC mode. This just sets basic linker flags.
|
|
|
805
|
|
|
806 @item ELLDLLFLAGS
|
|
|
807 @cindex @code{ELLDLLFLAGS}
|
|
|
808 Sets the flags passed to the linker that are required to created shared
|
|
|
809 and loadable objects.
|
|
|
810
|
|
|
811 @item ELLPICFLAGS
|
|
|
812 @cindex @code{ELLPICFLAGS}
|
|
|
813 Sets the C compiler option required to produce an object file that is
|
|
|
814 suitable for including in a shared library. This option should turn on
|
|
|
815 PIC mode, or the moral equivalent thereof on the target system.
|
|
|
816
|
|
|
817 @item ELLMAKEDOC
|
|
|
818 @cindex @code{ELLMAKEDOC}
|
|
|
819 Sets the name of the @file{make-docfile} program to use. Usually
|
|
|
820 @code{ellcc} will use the version that was compiled and installed with
|
|
|
821 @value{emacs}, but this option allows you to specify an alternative path.
|
|
|
822 Used during the compile phase of @value{emacs} itself.
|
|
|
823 @end table
|
|
|
824
|
|
|
825 @node Defining Functions, Defining Variables, Using ellcc, Top
|
|
|
826 @chapter Defining Functions
|
|
|
827 @cindex defining functions
|
|
|
828
|
|
|
829 One of the main reasons you would ever write a module is to
|
|
|
830 provide one or more @dfn{functions} for the user or the editor to use.
|
|
442
|
831 The term
|
|
428
|
832 @dfn{function} is a bit overloaded here, as it refers to both a C
|
|
|
833 function and the way it appears to Lisp, which is a @dfn{subroutine}, or
|
|
|
834 simply a @dfn{subr}. A Lisp subr is also known as a Lisp primitive, but
|
|
|
835 that term applies less to dynamic modules. @xref{Writing Lisp
|
|
|
836 Primitives,,,internals,@value{emacs} Internals Manual}, for details on how to
|
|
|
837 declare functions. You should familiarize yourself with the
|
|
442
|
838 instructions there. The format of the function declaration is identical
|
|
428
|
839 in modules.
|
|
|
840
|
|
442
|
841 Normal Lisp primitives document the functions they defining by including
|
|
428
|
842 the documentation as a C comment. During the build process, a program
|
|
|
843 called @file{make-docfile} is run, which will extract all of these
|
|
|
844 comments, build up a single large documentation file, and will store
|
|
|
845 pointers to the start of each documentation entry in the dumped @value{emacs}.
|
|
|
846 This, of course, will not work for dynamic modules, as they are loaded
|
|
|
847 long after @value{emacs} has been dumped. For this reason, we require a
|
|
|
848 special means for adding documentation for new subrs. This is what the
|
|
|
849 macro @code{CDOCSUBR} is used for, and this is used extensively during
|
|
|
850 @code{ellcc} initialization mode.
|
|
|
851
|
|
|
852 When using @code{DEFUN} in normal @value{emacs} C code, the sixth
|
|
|
853 ``parameter'' is a C comment which documents the function. For a
|
|
|
854 dynamic module, we of course need to convert the C comment to a usable
|
|
442
|
855 string, and we need to set the documentation pointer of the subr to this
|
|
428
|
856 string. As a module programmer, you don't actually need to do any work
|
|
|
857 for this to happen. It is all taken care of in the
|
|
|
858 @code{docs_of_module} function created by @code{ellcc}.
|
|
|
859
|
|
|
860 @menu
|
|
|
861 * Using DEFUN:: Using the DEFUN macro to define functions
|
|
|
862 * Declaring Functions:: Declaring functions to the Lisp reader
|
|
|
863 @end menu
|
|
|
864
|
|
|
865 @node Using DEFUN, Declaring Functions, Defining Functions, Defining Functions
|
|
|
866 @section Using @code{DEFUN}
|
|
|
867 @cindex subrs
|
|
|
868 @findex DEFUN
|
|
|
869 @cindex functions, Lisp
|
|
|
870 @cindex functions, defining
|
|
|
871
|
|
775
|
872 The full syntax of a function declaration is discussed in the
|
|
|
873 @value{emacs} internals manual in greater depth. @ref{Writing Lisp
|
|
|
874 Primitives,,,internals,@value{emacs} Internals Manual}. What follows is
|
|
|
875 a brief description of how to define and implement a new Lisp primitive
|
|
|
876 in a module. This is done using the @code{DEFUN} macro. Here is a
|
|
|
877 small example:
|
|
428
|
878
|
|
|
879 @example
|
|
|
880 @cartouche
|
|
|
881 DEFUN ("my-function", Fmy_function, 1, 1, "FFile name: ", /*
|
|
|
882 Sample Emacs primitive function.
|
|
|
883
|
|
442
|
884 The specified FILE is frobnicated before it is fnozzled.
|
|
428
|
885 */
|
|
|
886 (file))
|
|
|
887 @{
|
|
|
888 char *filename;
|
|
|
889
|
|
|
890 if (NILP(file))
|
|
|
891 return Qnil;
|
|
|
892
|
|
|
893 filename = (char *)XSTRING_DATA(file);
|
|
|
894 frob(filename);
|
|
|
895 return Qt;
|
|
|
896 @}
|
|
|
897 @end cartouche
|
|
|
898 @end example
|
|
|
899
|
|
|
900 The first argument is the name of the function as it will appear to the
|
|
442
|
901 Lisp reader. This must be provided as a string. The second argument is
|
|
428
|
902 the name of the actual C function that will be created. This is
|
|
442
|
903 typically the Lisp function name with a preceding capital @code{F}, with
|
|
428
|
904 hyphens converted to underscores. This must be a valid C function
|
|
|
905 name. Next come the minimum and maximum number of arguments,
|
|
|
906 respectively. This is used to ensure that the correct number of
|
|
|
907 arguments are passed to the function. Next is the @code{interactive}
|
|
|
908 definition. If this function is meant to be run by a user
|
|
|
909 interactively, then you need to specify the argument types and prompts
|
|
|
910 in this string. Please consult the @value{emacs} Lisp manual for more
|
|
|
911 details. Next comes a C comment that is the documentation for this
|
|
|
912 function. This comment @strong{must} exist. Last comes the list of
|
|
|
913 function argument names, if any.
|
|
|
914
|
|
|
915 @node Declaring Functions, , Using DEFUN, Defining Functions
|
|
|
916 @section Declaring Functions
|
|
|
917 @findex DEFSUBR
|
|
|
918 @cindex functions, declaring
|
|
|
919
|
|
|
920 Simply writing the code for a function is not enough to make it
|
|
442
|
921 available to the Lisp reader. You have to, during module
|
|
428
|
922 initialization, let the Lisp reader know about the new function. This
|
|
|
923 is done by calling @code{DEFSUBR} with the name of the function. This
|
|
|
924 is the sole purpose of the initialization function
|
|
|
925 @code{syms_of_module}. @xref{Required Functions}, for more details.
|
|
|
926
|
|
|
927 Each call to @code{DEFSUBR} takes as its only argument the name of the
|
|
|
928 function, which is the same as the second argument to the call to
|
|
|
929 @code{DEFUN}. Using the example function above, you would insert the
|
|
|
930 following code in the @code{syms_of_module} function:
|
|
|
931
|
|
|
932 @example
|
|
|
933 @cartouche
|
|
|
934 DEFSUBR(Fmy_function);
|
|
|
935 @end cartouche
|
|
|
936 @end example
|
|
|
937
|
|
|
938 This call will instruct @value{emacs} to make the function visible to the Lisp
|
|
|
939 reader and will prepare for the insertion of the documentation into
|
|
|
940 the right place. Once this is done, the user can call the Lisp
|
|
|
941 function @code{my-function}, if it was defined as an interactive
|
|
|
942 function (which in this case it was).
|
|
|
943
|
|
|
944 Thats all there is to defining and announcing new functions. The rules
|
|
|
945 for what goes inside the functions, and how to write good modules, is
|
|
|
946 beyond the scope of this document. Please consult the @value{emacs}
|
|
|
947 internals manual for more details.
|
|
|
948
|
|
|
949 @node Defining Variables, Index, Defining Functions, Top
|
|
|
950 @chapter Defining Variables
|
|
|
951 @cindex defining variables
|
|
|
952 @cindex defining objects
|
|
|
953 @findex DEFVAR_LISP
|
|
|
954 @findex DEFVAR_BOOL
|
|
|
955 @findex DEFVAR_INT
|
|
|
956 @cindex variables, Lisp
|
|
|
957 @cindex variables, defining
|
|
|
958 @cindex objects, defining
|
|
|
959 @cindex objects, Lisp
|
|
|
960
|
|
|
961 Rarely will you write a module that only contains functions. It is
|
|
|
962 common to also provide variables which can be used to control the
|
|
442
|
963 behavior of the function, or store the results of the function being
|
|
428
|
964 executed. The actual C variable types are the same for modules
|
|
|
965 and internal @value{emacs} primitives, and the declaration of the variables
|
|
|
966 is identical.
|
|
|
967
|
|
442
|
968 @xref{Adding Global Lisp Variables,,,internals,XEmacs Internals Manual},
|
|
428
|
969 for more information on variables and naming conventions.
|
|
|
970
|
|
|
971 Once your variables are defined, you need to initialize them and make
|
|
|
972 the Lisp reader aware of them. This is done in the
|
|
|
973 @code{vars_of_module} initialization function using special @value{emacs}
|
|
442
|
974 macros such as @code{DEFVAR_LISP}, @code{DEFVAR_BOOL}, @code{DEFVAR_INT}
|
|
|
975 etc. The best way to see how to use these macros is to look at existing
|
|
428
|
976 source code, or read the internals manual.
|
|
|
977
|
|
|
978 One @emph{very} important difference between @value{emacs} variables and
|
|
|
979 module variables is how you use pure space. Simply put, you
|
|
|
980 @strong{never} use pure space in @value{emacs} modules. The pure space
|
|
442
|
981 storage is of a limited size, and is initialized properly during the
|
|
428
|
982 dumping of @value{emacs}. Because variables are being added dynamically to
|
|
|
983 an already running @value{emacs} when you load a module, you cannot use pure
|
|
|
984 space. Be warned: @strong{do not use pure space in modules. Repeat, do
|
|
|
985 not use pure space in modules.} Once again, to remove all doubts:
|
|
|
986 @strong{DO NOT USE PURE SPACE IN MODULES!!!}
|
|
|
987
|
|
|
988 Below is a small example which declares and initializes two
|
|
|
989 variables. You will note that this code takes into account the fact
|
|
|
990 that this module may very well be compiled into @value{emacs} itself. This
|
|
|
991 is a prudent thing to do.
|
|
|
992
|
|
|
993 @example
|
|
|
994 @cartouche
|
|
|
995 Lisp_Object Vsample_string;
|
|
|
996 int sample_boolean;
|
|
|
997
|
|
|
998 void
|
|
|
999 vars_of_module()
|
|
|
1000 @{
|
|
|
1001 DEFVAR_LISP ("sample-string", &Vsample_string /*
|
|
|
1002 This is a sample string, declared in a module.
|
|
|
1003
|
|
|
1004 Nothing magical about it.
|
|
|
1005 */);
|
|
|
1006
|
|
|
1007 DEFVAR_BOOL("sample-boolean", &sample_boolean /*
|
|
|
1008 *Sample user-settable boolean.
|
|
|
1009 */);
|
|
|
1010
|
|
|
1011 sample_boolean = 0;
|
|
|
1012 Vsample_string = build_string("My string");
|
|
|
1013 @}
|
|
|
1014 @end cartouche
|
|
|
1015 @end example
|
|
|
1016
|
|
|
1017 @c Print the tables of contents
|
|
|
1018 @contents
|
|
|
1019 @c That's all
|
|
|
1020
|
|
|
1021 @node Index, , Defining Variables, Top
|
|
|
1022 @unnumbered Index
|
|
|
1023
|
|
|
1024 @printindex cp
|
|
|
1025
|
|
|
1026 @bye
|
|
|
1027
|
