RE: m68k cross: problems with crt0

["paul andrews" <paulwandrews at hotmail dot com>]

>hi,
>i have installed gcc as cross compiler for an mc68332 embedded system. but 
>i failed with this initialization stuff. i also wonder about this
>__main, __do_global_ctors() function and the __INIT_SECTION__ in
>the linker script.
>i hope that someone can help me with this stuff.

__main, __do_global_ctors etc is the generic gcc startup code, which is
actually initialising global c++ constructors. This is fairly harmless
if you only use c. These routines are found in libgcc - hunt around for
it and include it in your link.

>modified the crt0.S file which comes with newlib.
>small programs work. but global and static variables are
>uninitialized. also library function like sprintf() don't
>work.

I completely re-wrote the crt0.s for use in our system as I didn't
need much of the stuff it was doing. I also noticed that you don't need
to specify it on your link line: ld seems to magically find it.

>what's about the function __do_global_ctors(). is that
>the place where this stuff should be done?

No. This function is part of the gcc helper library. crt0.s is the place.

I also re-wrote the ld script, again because I though it was overly complex.
Below are both my crt0.s and .ld script which may help you...or may not :-)

Paul Andrews
Software Engineer
Smartmove (NZ) Ltd
Auckland, New Zealand
http://www.smartmove.co.nz

----------------------------------------------------------------------------
-----
crt0.s
----------------------------------------------------------------------------
-----

	.extern main
	.extern _etext
	.extern _edata
	.extern _sdata
	.global start

/*--------------------------------------------------------------------------
--*/
  .section .bss

stkbot:
  .ds.b   4096
stktop:

/*--------------------------------------------------------------------------
--*/
	.section .sig

    .ascii  "The quick brown fox jumps over the lazy dog"

/*--------------------------------------------------------------------------
--*/
	.section .vectors

	.long _etext
	.long start
/*--------------------------------------------------------------------------
--*/
	.text

start:
	move.l  #stktop,%a7	/* set up the stack */

	move.l  #_etext,%a0	/* copy initialised data back to ram */
	move.l  #_sdata,%a1

loop:
	move.b  (%a0)+,(%a1)+
	cmp.l   #_edata,%a1
	blt.s   loop

	jmp	main

/*--------------------------------------------------------------------------
--*/
/* EOF  */

----------------------------------------------------------------------------
-----
cad.ld
----------------------------------------------------------------------------
-----
/*
		CAD3 linker script.
*/

STARTUP(crt0.o)
OUTPUT_ARCH(m68k)
/* formats: srec coff-m68k */
OUTPUT_FORMAT(coff-m68k)
SEARCH_DIR(D:\gnu\gcc-m68k\m68k-coff\lib\m68000)
/* for libgcc.a */
SEARCH_DIR(D:\GNU\gcc-m68k\lib\gcc-lib\m68k-coff\2.95.2)
MEMORY
{
	ram(RWX) : ORIGIN = 0, LENGTH = 512K
	flash(RX) : ORIGIN = 0x400000, LENGTH = 512K
}


SECTIONS
{
/* RAM */
	.vectorspace 0x000000:
	{
		*(.vectorspace)
	} > ram

	.data 0x8000:
	AT( ADDR(.text) + SIZEOF(.text) )
	{
		_sdata = .;    /* store start address as symbol*/
		*(.data)
		_edata = .;   /* store end address as symbol */
	} > ram   /* the >ram and >flash do nothing but provide extra
checking */

	.bss :
	{
		*(.bss)
	} > ram     /* use '> ram' to see if it all still fits */

	.stack :
	{
		*(.stack)
		end = .;	/* sbrk.c in libnosys wants this for some
reason */
	} > ram


/* ROM */
	.vectors 0x408000:
	{
		*(.vectors)
	} > flash

	.signature 0x408400 :
	{
		*(.sig)
	} > flash

	.text 0x408500 :
	{
		*(.text)

     . = ALIGN(4);		/* this keep the __do_global_ctors happy */
     __CTOR_LIST__ = .;
     LONG((__CTOR_END__ - __CTOR_LIST__) / 4 - 2)
     *(.ctors)
     LONG(0)
     __CTOR_END__ = .;


		_etext = ABSOLUTE(.) ;

	} > flash

}

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com