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466
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1 <chapter>
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2 <title>The C Compiler System</title>
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3
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4 <section>
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5 <title>Introduction</title>
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6 <para>
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468
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7 The "C" programming language is rapidly growing in popularity
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8 and seems destined to become one of the most popular programming
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9 languages used for microcomputers. The rapid rise in the use of C
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10 is not surprising. C is an incredibly versatile and efficient
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11 language that can handle tasks that previously would have required
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12 complex assembly language programming.
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466
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13 </para>
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530
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14 <para>
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15 C was originally developed at Bell Telephone Laboratories as an
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16 implementation language for the UNIX operating system by Brian
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17 Kernighan and Dennis Ritchie. They also wrote a book titled <quote>The
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18 C Programming Language</quote> which is universally accepted as the standard
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19 for the language. It is an interesting reflection on the language
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20 that although no formal industry-wide <quote>standard</quote> was ever developed
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21 for C, programs written in C tend to be far more portable between
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22 radically different computer systems as compared to so-called
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23 <quote>standardized</quote> languages such as BASIC, COBOL, and PASCAL. The
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24 reason C is so portable is that the language is so inherently
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25 expandable that is some special function is required, the user can
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26 create a portable extension to the language, as opposed to the
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27 common practice of adding additional statements to the language.
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28 For example, the number of special-purpose BASIC dialects defies all
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29 reason. A lesser factor is the underlying UNIX operating system,
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30 which is also sufficiently versatile to discourage bastardization of
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31 the language. Indeed, standard C compilers and Unix are intimately
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32 related.
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33 </para>
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34 <para>
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35 Fortunately, the 6809 microprocessor, the OS-9 operating
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36 system, and the C language form an outstanding combination. The
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37 6809 was specifically designed to efficiently run high-level
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38 languages, and its stack-oriented instruction set and versatile
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39 repertoire of addressing modes handle the C language very well. As
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40 mentioned previously, UNIX and C are closely related, and because
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41 OS-9 is derived from UNIX, it also supports C to the degree that
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42 almost any application written in C can be transported from a UNIX
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43 system to an OS-9 system, recompiled, and correctly executed.
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44 </para>
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466
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45 </section>
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46 <section>
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468
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47 <title>The Language Implementation</title>
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466
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48 <para>
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468
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49 OS-9 C is implemented almost exactly as described in 'The C
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50 Programming Language' by Kernighan and Ritchie (hereafter referred
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51 to as K&R).
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52 </para>
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53 <para>
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54 Allthough this version of C follows the specification faithfully,
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55 there are some differences. The differences mostly reflect
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56 parts of C that are obsolete or the constraints imposed by memory
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57 size limitations.
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466
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58 </para>
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530
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59 </section>
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472
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60
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530
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61 <section>
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62 <title>Differences from the K & R Specification</title>
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63 <para>
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64 </para>
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472
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65 </section>
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530
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66
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67 <section>
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68 <title>Enhancements and Extensions</title>
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69
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70 <section>
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71 <title>The <quote>Direct</quote> Storage Class</title>
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72 <para>
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73 </para>
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74 </section>
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75
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76 <section>
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77 <title>Embedded Assembly Language</title>
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78 <para>
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79 </para>
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80 </section>
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81
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82 <section>
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83 <title>Control Character Escape Sequences</title>
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84 <para>
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85 </para>
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86 </section>
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87 </section>
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88
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89 <section>
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90 <title>Implementation-dependent Characteristics</title>
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91 <para>
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92 </para>
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93
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94 <section>
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95 <title>Data Representation and Storage Requirements</title>
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96 <para>
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97 </para>
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98 </section>
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99
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100 <section>
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101 <title>Register Variables</title>
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102 <para>
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103 </para>
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104 </section>
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105
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106 <section>
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107 <title>Access To Command Line Parameters</title>
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108 <para>
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109 </para>
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110 </section>
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111 </section>
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112
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113 <section>
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114 <title>System Calls and the Standard Library</title>
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115
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116 <section>
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117 <title>Operating System Calls</title>
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118 <para>
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119 </para>
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120 </section>
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121
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122 <section>
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123 <title>The Standard Library</title>
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124 <para>
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125 </para>
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126 </section>
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127 </section>
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128
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129 <section>
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130 <title>Run-time Arithmetic Error Handling</title>
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131 <para>
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132 </para>
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133 </section>
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134
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135 <section>
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136 <title>Achieving Maximum Program Performance</title>
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137 <para>
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138 </para>
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139
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140 <section>
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141 <title>Programming Considerations</title>
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142 <para>
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143 </para>
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144 </section>
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145
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146 <section>
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147 <title>The Optimizer Pass</title>
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148 <para>
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149 </para>
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150 </section>
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151
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152 <section>
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153 <title>The Profiler</title>
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154 <para>
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155 </para>
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156 </section>
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157 </section>
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158
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159 <section>
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160 <title>C Compiler Component Files and File Usage</title>
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161 <para>
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162 </para>
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163
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164 <section>
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165 <title>Temporary Files</title>
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166 <para>
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167 </para>
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168 </section>
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169 </section>
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170
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171 <section>
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172 <title>Running the Compiler</title>
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173 <para>
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174 </para>
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175 </section>
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176
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472
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177 <section>
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178 <title>Compiler Option Flags</title>
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179 <para>
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180 The compiler recognizes several command-line option flags which
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181 modify the compilation process where needed. All flags are
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182 recognized before compilation commences so the flags may be placed
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183 anywhere on the command line. Flags may be ran together as in "-ro",
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184 except where a flag is followed by something else; see "-f=" and
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185 "-d" for examples.
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186 </para>
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187 <para>
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188 -A
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189 suppresses assembly, leaving the output as assembler code in a
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190 file whose name is postfixed ".a".
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191 </para>
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192 <para>
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193 -E=<number>
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194 Set the edition number constant byte to the number given. This is
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195 an OS-9 convention for memory modules.
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196 </para>
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197 <para>
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198 -O
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199 inhibits the assembly code optimizer pass. The optimizer will
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200 shorten object code by about 11% with a comparable increase in speed
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201 and is recommended for production versions of de-bugged programs.
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202 </para>
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203 <para>
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204 -P
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205 invokes the profiler to generate function frequency
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206 statistics after program execution.
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207 </para>
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208 <para>
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209 -R
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210 suppresses linking library modules into an executable program.
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211 Outputs are left in files with postfixes ".r".
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212 </para>
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213 <para>
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214 -M=<memory size>
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215 will instruct the linker to allocate <memory size>
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216 for data, stack, and parameter area. Memory size may be expressed
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217 in pages (an integer) or in kilobytes by appending "k" to an
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218 integer. For more details of the use of this option, see the
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219 "Memory Management" section of this manual.
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220 </para>
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221 <para>
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222 -L=<filename>
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223 specifies a library to be searched by the linker
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224 before the Standard Library and system interface.
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225 </para>
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226 <para>
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227 -F=<path>
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228 overrides the above output file naming. The output file
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229 will be left with <filename> as its name. This flag does not make
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230 sense in multiple source mode, and either the -a or -r flag is also
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231 present. The module will be called the last name in <path>.
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232 </para>
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233 <para>
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234 -C
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235 will output the source code as comments with the assembler code.
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236 </para>
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237 <para>
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238 -S
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239 stops the generation of stack-checking code. -S should only be
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240 used with great care when the appication is extremely time-critical
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241 and when the use of the stack by compiler generated code is fully
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242 understood.
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243 </para>
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244 <para>
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245 -D<identifier>
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246 is equivalent to "#define <identifier>" written in
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247 the source file. -D is useful where different versions of a program
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248 are maintained in one source file and differentiated by means of the
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249 "#ifdef" of "#ifndef" pre-processor directives. If the <identifier>
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250 is used as a macro for expansion by the pre-processor, "1"(one) will
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251 be the expanded "value" unless the form "-d<identifier>=<string>" is
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252 used in which case the expansion will be <string>.
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253 </para>
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254 <table frame="none">
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255 <title>Command Line and Option Flag Examples</title>
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256 <tgroup cols="3">
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257 <colspec colwidth="1.5in" colname="c1">
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258 <colspec colwidth="1.5in" colname="c2">
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259 <colspec colwidth="1.5in" colname="c3">
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260 <thead>
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261 <row>
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262 <entry>command line</entry>
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263 <entry>action</entry>
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264 <entry>output file(s)</entry>
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265 </row>
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266 </thead>
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267 <tbody>
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268 <row>
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269 <entry>cc prg.c</entry>
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270 <entry>compile to an executable program</entry>
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271 <entry>prg</entry>
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272 <entry></entry>
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273 </row>
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274 <row>
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275 <entry>cc prg.c -a</entry>
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276 <entry>compile to assembly language source code</entry>
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277 <entry>prg.a</entry>
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278 </row>
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279 <row>
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280 <entry>cc prg.c -r</entry>
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281 <entry>compile to relocatable module</entry>
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282 <entry>prg.r</entry>
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283 </row>
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284 <row>
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285 <entry>cc prg1.c prg2.c prg3.c</entry>
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286 <entry>compile to executable program</entry>
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287 <entry>prg1.r, prg2.r, prg3.r, output</entry>
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288 </row>
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289 <row>
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290 <entry>cc prg1.c prg2.a prg3.r</entry>
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291 <entry>compile prg1.c, assemble prg2.a and combine all into
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292 and executable program</entry>
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293 <entry>prg1.r, prg2.r</entry>
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294 </row>
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295 <row>
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296 <entry>cc prg1.c prg2.c -a</entry>
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297 <entry>compile to assembly language source code</entry>
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298 <entry>prg1.a, prg2.a</entry>
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299 </row>
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300 <row>
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301 <entry>cc prg1.c prg2.c -f=prg</entry>
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302 <entry>compile to executable program</entry>
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303 <entry>prg</entry>
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304 </row>
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305 </tbody>
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306 </tgroup>
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307 </table>
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308
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466
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309 </section>
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310 </chapter>
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