On Mon, Apr 25, 2005 at 03:22:31PM +0000, Joseph S. Myers wrote:
> On Mon, 25 Apr 2005, Martin Koegler wrote:
>
> > The solution would be to add also for the base type of an array the
> > eeprom attribute. Additonally all elements of structures and unions must
> > also have the eeprom attribute added.
>
> The solution is to implement DTR18037 named address spaces. Naturally
> such implementation involves implementing the proper semantics for the
> types of structure element references.
As I don't know DTR18037 and have no access to it (even Google finds nothing
useable about it), I
cannot say something about it.
I intend to create different address spaces in GCC using attributes, with only
small changes in the core.
As I test my ideas on my m68hc05 port, I describe my intended semantics using
it,
which is (apart for the problem with the incorrect types) already working:
// shortcut for the attribute to write more compact
#define E __attribute__ ((eeprom))
// An integer in the eeprom
// for my port, I do the section selection using an other attribute
int x E;
typedef int eint E;
struct x{
int x;
int y;
}
struct y{
int x;
struct x y;
}
typedef struct y ey E;
struct y z E;
struct y z1;
int a[5] E;
eint* a1;
int* a2;
int tmp;
tmp=z.y.x; //do a load from the eeprom, in my case the same as a normal load
z.y.x=2; //do a store to the eeprom
a2=&z.y.x; //assignment of incompatible pointers
*a2=1; //undefined
a1=&z.y.x;
*a1=1; // write to eeprom at z.y.x
a[2]=1; // write to eeprom
a1=a+1; // ok
*a1=3; // write to a[1] in eeprom
a2=a+1 //assignment of incomatible pointers
*a1=3 //undefined
void test(ey* ptr)
{
ptr->x=1; // write to eeprom
}
test(&z); //call test with z -> write 1 to z.x in the eeprom.
z1=z // fails currently with a type error, but this should also work (copy from
eeprom to z1)
In the case of my port, a read using a normal pointer, which is load from a
eeprom pointer, will succeed,
in the case of AVR, such a operation will also be undefined.
mfg Martin Kögler
[EMAIL PROTECTED]
