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<h4 class="subsection">The Location Counter</h4>



   <p>The special linker variable <dfn>dot</dfn> <code>.</code> always contains the

current output location counter.  Since the <code>.</code> always refers to a

location in an output section, it may only appear in an expression

within a <code>SECTIONS</code> command.  The <code>.</code> symbol may appear

anywhere that an ordinary symbol is allowed in an expression.



   <p>Assigning a value to <code>.</code> will cause the location counter to be

moved.  This may be used to create holes in the output section.  The

location counter may never be moved backwards.



<pre class="smallexample">     SECTIONS

     {

       output :

         {

           file1(.text)

           . = . + 1000;

           file2(.text)

           . += 1000;

           file3(.text)

         } = 0x12345678;

     }

     </pre>



<p>In the previous example, the <code>.text</code> section from <code>file1</code> is

located at the beginning of the output section <code>output</code>.  It is

followed by a 1000 byte gap.  Then the <code>.text</code> section from

<code>file2</code> appears, also with a 1000 byte gap following before the

<code>.text</code> section from <code>file3</code>.  The notation <code>= 0x12345678</code>

specifies what data to write in the gaps (see <a href="Output-Section-Fill.html#Output%20Section%20Fill">Output Section Fill</a>).



   <p>Note: <code>.</code> actually refers to the byte offset from the start of the

current containing object.  Normally this is the <code>SECTIONS</code>

statement, whoes start address is 0, hence <code>.</code> can be used as an

absolute address.  If <code>.</code> is used inside a section description

however, it refers to the byte offset from the start of that section,

not an absolute address.  Thus in a script like this:



<pre class="smallexample">     SECTIONS

     {

         . = 0x100

         .text: {

           *(.text)

           . = 0x200

         }

         . = 0x500

         .data: {

           *(.data)

           . += 0x600

         }

     }

     </pre>



   <p>The <code>.text</code> section will be assigned a starting address of 0x100

and a size of exactly 0x200 bytes, even if there is not enough data in

the <code>.text</code> input sections to fill this area.  (If there is too

much data, an error will be produced because this would be an attempt to

move <code>.</code> backwards).  The <code>.data</code> section will start at 0x500

and it will have an extra 0x600 bytes worth of space after the end of

the values from the <code>.data</code> input sections and before the end of

the <code>.data</code> output section itself.



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