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1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
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2 <HTML
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3 ><HEAD
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4 ><TITLE
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5 >Linker Operation</TITLE
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6 ><META
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7 NAME="GENERATOR"
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8 CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
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9 REL="HOME"
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10 TITLE="LW Tool Chain"
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11 HREF="index.html"><LINK
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12 REL="UP"
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13 TITLE="LWLINK"
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14 HREF="c436.html"><LINK
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15 REL="PREVIOUS"
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16 TITLE="LWLINK"
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17 HREF="c436.html"><LINK
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18 REL="NEXT"
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19 TITLE="Linking Scripts"
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20 HREF="x524.html"></HEAD
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21 ><BODY
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22 CLASS="SECTION"
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23 BGCOLOR="#FFFFFF"
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24 TEXT="#000000"
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25 LINK="#0000FF"
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26 VLINK="#840084"
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27 ALINK="#0000FF"
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28 ><DIV
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29 CLASS="NAVHEADER"
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30 ><TABLE
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31 SUMMARY="Header navigation table"
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32 WIDTH="100%"
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33 BORDER="0"
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34 CELLPADDING="0"
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35 CELLSPACING="0"
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36 ><TR
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37 ><TH
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38 COLSPAN="3"
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39 ALIGN="center"
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40 >LW Tool Chain</TH
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41 ></TR
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42 ><TR
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43 ><TD
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44 WIDTH="10%"
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45 ALIGN="left"
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46 VALIGN="bottom"
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47 ><A
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48 HREF="c436.html"
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49 ACCESSKEY="P"
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50 >Prev</A
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51 ></TD
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52 ><TD
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53 WIDTH="80%"
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54 ALIGN="center"
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55 VALIGN="bottom"
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56 >Chapter 4. LWLINK</TD
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57 ><TD
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58 WIDTH="10%"
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59 ALIGN="right"
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60 VALIGN="bottom"
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61 ><A
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62 HREF="x524.html"
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63 ACCESSKEY="N"
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64 >Next</A
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65 ></TD
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66 ></TR
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67 ></TABLE
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68 ><HR
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69 ALIGN="LEFT"
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70 WIDTH="100%"></DIV
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71 ><DIV
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72 CLASS="SECTION"
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73 ><H1
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74 CLASS="SECTION"
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75 ><A
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76 NAME="AEN510"
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77 >4.2. Linker Operation</A
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78 ></H1
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79 ><P
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80 >LWLINK takes one or more files in the LWTOOLS object file format and links
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81 them into a single binary. While the precise method is slightly different,
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82 linking can be conceptualized as the following steps.</P
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83 ><P
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84 ></P
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85 ><OL
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86 TYPE="1"
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87 ><LI
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88 ><P
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89 >First, the linker loads a linking script. If no script is specified, it
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90 loads a built-in default script based on the output format selected. This
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91 script tells the linker how to lay out the various sections in the final
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92 binary.</P
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93 ></LI
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94 ><LI
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95 ><P
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96 >Next, the linker reads all the input files into memory. At this time, it
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97 flags any format errors in those files. It constructs a table of symbols
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98 for each object at this time.</P
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99 ></LI
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100 ><LI
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101 ><P
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102 >The linker then proceeds with organizing the sections loaded from each file
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103 according to the linking script. As it does so, it is able to assign addresses
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104 to each symbol defined in each object file. At this time, the linker may
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105 also collapse different instances of the same section name into a single
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106 section by appending the data from each subsequent instance of the section
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107 to the first instance of the section.</P
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108 ></LI
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109 ><LI
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110 ><P
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111 >Next, the linker looks through every object file for every incomplete reference.
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112 It then attempts to fully resolve that reference. If it cannot do so, it
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113 throws an error. Once a reference is resolved, the value is placed into
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114 the binary code at the specified section. It should be noted that an
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115 incomplete reference can reference either a symbol internal to the object
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116 file or an external symbol which is in the export list of another object
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117 file.</P
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118 ></LI
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119 ><LI
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120 ><P
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121 >If all of the above steps are successful, the linker opens the output file
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122 and actually constructs the binary.</P
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123 ></LI
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124 ></OL
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125 ></DIV
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126 ><DIV
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127 CLASS="NAVFOOTER"
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128 ><HR
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129 ALIGN="LEFT"
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130 WIDTH="100%"><TABLE
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131 SUMMARY="Footer navigation table"
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132 WIDTH="100%"
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133 BORDER="0"
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134 CELLPADDING="0"
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135 CELLSPACING="0"
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136 ><TR
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137 ><TD
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138 WIDTH="33%"
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139 ALIGN="left"
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140 VALIGN="top"
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141 ><A
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142 HREF="c436.html"
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143 ACCESSKEY="P"
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144 >Prev</A
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145 ></TD
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146 ><TD
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147 WIDTH="34%"
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148 ALIGN="center"
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149 VALIGN="top"
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150 ><A
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151 HREF="index.html"
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152 ACCESSKEY="H"
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153 >Home</A
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154 ></TD
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155 ><TD
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156 WIDTH="33%"
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157 ALIGN="right"
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158 VALIGN="top"
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159 ><A
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160 HREF="x524.html"
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161 ACCESSKEY="N"
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162 >Next</A
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163 ></TD
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164 ></TR
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165 ><TR
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166 ><TD
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167 WIDTH="33%"
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168 ALIGN="left"
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169 VALIGN="top"
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170 >LWLINK</TD
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171 ><TD
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172 WIDTH="34%"
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173 ALIGN="center"
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174 VALIGN="top"
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175 ><A
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176 HREF="c436.html"
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177 ACCESSKEY="U"
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178 >Up</A
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179 ></TD
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180 ><TD
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181 WIDTH="33%"
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182 ALIGN="right"
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183 VALIGN="top"
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184 >Linking Scripts</TD
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185 ></TR
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186 ></TABLE
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187 ></DIV
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188 ></BODY
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189 ></HTML
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190 > |
