C18 compiler. struct issues.

HerbertMunch · Dec 29, 2007

Im trying to make a member of this struct reference another instance of the same struct.

Code:

typedef struct MenuItem
{
	
	//Pointer to the an array of menuitems that represents the next level of heirarchy.
	MenuItem *nextLevel;
	
	

}MenuItem;

The compiler is not happy.
Can this not be done in c?

HerbertMunch · Dec 29, 2007

Would it be okay to do this instead, and then cast later?

Code:

typedef struct MenuItem
{
	
	//Pointer to the an array of menuitems that represents the next level of heirarchy.
	void *nextLevel;
	
	

}MenuItem;

Thanks

Pommie · Dec 29, 2007

Would it be,

Code:

typedef struct MenuItem
{
	
	//Pointer to the an array of menuitems that represents the next level of heirarchy.
	near rom * MenuItem;

}MenuItem;

Mike.

Pommie · Dec 29, 2007

BTW, I added a message print routine to your code that uses a rom pointer.

Code:

void PutMessage(char rom*);
void PutMessageAt(unsigned char,unsigned char,char rom*);


void main(void){
    InitLCD();
    PutMessage((rom char*) "Hello World!");
    PutMessageAt(3,2,(rom char*) "3 in on Line 2");
    while(1);
}

//Write a string to the LCD
void PutMessage(char rom *Message){
	while(*Message!=0)
	    WriteChar(*Message++);
}

//Set position and write string.
void PutMessageAt(unsigned char X,unsigned char Y,char rom *Message){
    WriteCommand(0x80+(--Y<<6)+--X);
	while(*Message!=0)
	    WriteChar(*Message++);
}

Mike.

HerbertMunch · Dec 30, 2007

Ok thanks mike.

out of interest, which memory would my old code point to?

Thanks.

Mike - K8LH · Dec 30, 2007

Pommie said:

BTW, I added a message print routine to your code that uses a rom pointer.

Code:

void PutMessage(char rom*);
void PutMessageAt(unsigned char,unsigned char,char rom*);


void main(void){
    InitLCD();
    PutMessage((rom char*) "Hello World!");
    PutMessageAt(3,2,(rom char*) "3 in on Line 2");
    while(1);
}

//Write a string to the LCD
void PutMessage(char rom *Message){
    while(*Message!=0)
        WriteChar(*Message++);
}

//Set position and write string.
void PutMessageAt(unsigned char X,unsigned char Y,char rom *Message){
    WriteCommand(0x80+(--Y<<6)+--X);
    while(*Message!=0)
        WriteChar(*Message++);
}

Mike.

Nicely done Mike. A wonderful example using pointers which has thus far eluded and confounded me.

Pommie · Dec 30, 2007

Pointers on the pic are confusing. The default is that pointers point to ram. I'm slowly getting comfortable with the types of pic pointers and have just realised that the cast on the function call is now not needed, this is from when I was trying everything to get it working.

So,

Code:

        PutMessage("Hello World!");

Should work fine.

Mike.

HerbertMunch · Dec 30, 2007

Pommie said:
Pointers on the pic are confusing. The default is that pointers point to ram. I'm slowly getting comfortable with the types of pic pointers and have just realised that the cast on the function call is now not needed, this is from when I was trying everything to get it working.

So,

Code:

PutMessage("Hello World!");

Should work fine.

Mike.

ok thanks very much mate.

C18 compiler. struct issues.

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