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Linker documentation patch
- To: binutils@sourceware.cygnus.com
- Subject: Linker documentation patch
- From: Nick Clifton <nickc@cygnus.com>
- Date: Tue, 22 Jun 1999 17:48:11 +0100
Hi Guys,
Any comments on the enclosed patch to ld.texinfo ? It attempts to
explain the difference between using dot in a linker script when it
is between section statements or inside section statements. The
behaviour inside section statements is slightly non-intuitive, so I
thought it worthwhile adding a few paragraphs describing it.
Cheers
Nick
1999-06-22 Nick Clifton <nickc@cygnus.com>
* ld.texinfo (Location Counter): Describe behaviour of
location counter inside section statements.
Index: ld.texinfo
===================================================================
RCS file: /cvs/cvsfiles/devo/ld/ld.texinfo,v
retrieving revision 1.164
diff -p -r1.164 ld.texinfo
*** ld.texinfo 1999/06/20 17:46:32 1.164
--- ld.texinfo 1999/06/22 16:44:57
*************** followed by a 1000 byte gap. Then the @
*** 3410,3415 ****
--- 3410,3448 ----
@samp{.text} section from @file{file3}. The notation @samp{= 0x1234}
specifies what data to write in the gaps (@pxref{Output Section Fill}).
+ @cindex dot inside sections
+ Note: @code{.} actually refers to the byte offset from the start of the
+ current containing object. Normally this is the @code{SECTIONS}
+ statement, whoes start address is 0, hence @code{.} can be used as an
+ absolute address. If @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:
+
+ @smallexample
+ SECTIONS
+ @{
+ . = 0x100
+ .text: @{
+ *(.text)
+ . = 0x200
+ @}
+ . = 0x500
+ .data: @{
+ *(.data)
+ . += 0x600
+ @}
+ @}
+ @end smallexample
+
+ The @samp{.text} 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 @samp{.text} 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{.} backwards). The @samp{.data} section will start at 0x500
+ and it will have an extra 0x400 bytes worth of space after the end of
+ the values from the @samp{.data} input sections and before the end of
+ the @samp{.data} output section itself.
+
@need 2000
@node Operators
@subsection Operators