[Dprglist] gcc compiler/linker question - how to force code at given memory location?

[Dave Hylands]

You need to create a linker script file and use that to control where
things go.

The linker controls things using object files and sections. By default,
functions go into .text sections. There are compiler options which cause
each function to go into a separate section.

The syntax in the linker script files is a bit arcane.
https://ftp.gnu.org/old-gnu/Manuals/ld-2.9.1/html_chapter/ld_3.html#SEC6

Here's an example linker file used on an STM32F103 microcontroller and it
places the isr vectors at address 0x8002000.
https://github.com/dhylands/stm32-test/blob/master/board-STM32F103-Mini/STM32F103RBTx_FLASH.ld

This linker file shows putting particular object files into a particular
section:
https://github.com/micropython/micropython/blob/master/ports/stm32/boards/common_ifs.ld#L35


On Thu, Jan 30, 2020 at 12:55 PM Clayton Timmons via DPRGlist <
dprglist at lists.dprg.org> wrote:

>
> I'm searching for an answer to a simple question.  My friend Google tried
> to help but so far Google hasn't given me a good answer.   I'm hoping some
> savvy DPRG member probably has the wisdom I seek.
>
>
>
> I'm using a microchip processor writing code in C.   The code consists of
> several C source files which are compiled into object code then linked
> together.  Something like this simplified example.
>
> gcc -c   foo.c             <<<  compile C code into object file
> gcc -c   bar.c             <<<  compile C code into object file
>
> gcc   foo.o  bar.o   -o  foobar.cof     <<<  link all object files together
>
> The final output is in cof format which is converted to hex format used by
> the programmer.   There is a map file created by the linker which allows me
> to see where all the C functions end up in memory, something like this.
>
> External Symbols in Program Memory (by address):
>
>                      .  .  .
>                   0x003b18                  _foo
>                      .  .  .
>                   0x003e1e                  _bar
>
>
> My question is -   How can I force the linker to put a specific function
> at a specific location?     Say I want the function bar to start at
> 0x004000.
>
> There should be some compiler or linker directives to accomplish that.
>
> Any help is appreciated.
>
> -Clay Timmons-
>
>
>
>
>
>
>
>
>
> _______________________________________________
> DPRGlist mailing list
> DPRGlist at lists.dprg.org
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>


-- 
Dave Hylands
Peachland, BC, Canada
http://www.davehylands.com
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