学步园

SECTIONS
{
  . = 0x10000;
  .text : { *(.text) }
  . = 0x8000000;
  .data : { *(.data) }
  .bss : { *(.bss) }
}

   The first line inside the `SECTIONS' command of the above example

sets the value of the special symbol `.', which is the location

counter.  If you do not specify the address of an output section in some

other way (other ways are described later), the address is set from the

current value of the location counter.  The location counter is then

incremented by the size of the output section.  At the start of the

`SECTIONS' command, the location counter has the value `0'.

   The second line defines an output section, `.text'.  The colon is

required syntax which may be ignored for now.  Within the curly braces(小括号)

after the output section name, you list the names of the input sections

which should be placed into this output section. The `*' is a wildcard

which matches any file name.  The expression `*(.text)' means all

`.text' input sections in all input files.

   Since the location counter is `0x10000' when the output section

`.text' is defined, the linker will set the address of the `.text'

section in the output file to be `0x10000'.

   The remaining lines define the `.data' and `.bss' sections in the

output file. The linker will place the `.data' output section at

address `0x8000000'.  After the linker places the `.data' output

section, the value of the location counter will be `0x8000000' plus the

size of the `.data' output section.  The effect is that the linker will

place the `.bss' output section immediately after the `.data' output

section in memory.

   The linker will ensure that each output section has the required

alignment, by increasing the location counter if necessary.  In this

example, the specified addresses for the `.text' and `.data' sections

will probably satisfy any alignment constraints, but the linker may

have to create a small gap between the `.data' and `.bss' sections.