RE: [avr-gcc-list] why the pointer get a error address?

[Dave Hylands]

I'm not sure why it isn't working, But I thought I'd make a comment on the 
const stuff.

    const char *p1;     declares a pointer to a constant character.

When reading pointer stuff, start at the * and go left.

        char const *p2; is the same thing (char const and const char are 
synnonomous).

        char * const p3;        declares a constant pointer to a character 
(this one has to be initialized);

        const char * const p4;  delcares a constant pointer to a constant 
character (also has to be initalized when declared).

This little sample is perfectly fine:

        const char *s;

        s = "str";

        while ( *s != 0 )
        {
                ... Do something with *s ...
        
                s++;
        }

But you're not allowed to do this:

        const char *s;

        s = "str";

        *s = 'S';

So, it's important to differentiate between the pointer and the stuff the 
pointer points at.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/


> -----Original Message-----
> From: address@hidden 
> [mailto:address@hidden On Behalf Of Fabian Braun
> Sent: Saturday, February 14, 2004 12:22 AM
> To: address@hidden
> Subject: AW: [avr-gcc-list] why the pointer get a error address?
> 
> 
> 
> Hy whiteman
> 
> As far as I know: If you declare a constant value you also 
> have to define its value in the same line eg. (const char x = 
> 5;). I'm not very sure, could also be compiler dependent but 
> I learned that you never can assing a value to a const 
> variable in the programme like (charcter_pnt = test_array;).
> 
> Might be a fault :-)
> 
> /FaB
> -----Ursprüngliche Nachricht-----
> Von: address@hidden 
> [mailto:address@hidden Im > Auftrag von 
> whiteman
> Gesendet: Samstag, 14. Februar 2004 02:28
> An: avr-gcc-list
> Betreff: [avr-gcc-list] why the pointer get a error address?
> 
> hi,all！
>    I defined a array in program space and a pointer to this array.
> eg:
> 
> 
> uint8_t test_array[] PROGMEM = {
>       1,2,3,4,5,6,7
> };
> const prog_char *character_pnt;
> 
> void main(void)
> {
>       charcter_pnt = test_array;
>       ;
>       ;
> }
> 
> but when I simulated with avr_studio, I found the 
> "character_pnt" get a error address,The "*character_pnt" 
> isn't equal to 1.why?
> 
>       
> Regards                               
> 
> 　　　　　　　　whiteman
> address@hidden
> 　　　　　　　　　　2004-02-14
> 
> 
> 
> 
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