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Having to Cast a pointer for 8 bits??

 
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Tom Jetland



Joined: 23 Jun 2011
Posts: 31
Location: UK

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Having to Cast a pointer for 8 bits??
PostPosted: Wed Aug 31, 2011 11:01 am     Reply with quote
Hi.

18F4620
V4.124

I'm accessing stored data in ROM using a pointer and the

Code:
rom int8 scale[69]= { 0x45,0x5A ... }; etc.


method of storing in ROM (Program Memory).

I'm passing the pointer address to a function as follows :-

Code:
void draw_sprite (rom int8 * sprite_ptr);


and copying the data at the location of the pointer to an int8 variable called gfx_data as follows:-

Code:
gfx_data = *sprite_ptr;


This worked in version V4.099 (old I know!)

but now I have to change the code to...

Code:
gfx_data = (int8)*sprite_ptr;


to get it to work (if not, the next address after gfx_data is overwritten!)

is this part of the change made to suit ANSI as in the readme file? i.e.

Code:
Users that have old code with expresions of the form:
            *(&data + i)
need to change them to:
            *((int8 *)(&data) + i)
A compiler change was made to be ANSI compliant.



Thanks,

Tom

Last edited by Tom Jetland on Thu Sep 01, 2011 2:00 am; edited 1 time in total
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Aug 31, 2011 12:10 pm     Reply with quote
I got the same thing. I made a test program for you. I found the failure
starts at vs. 4.122 and continues through vs. 4.124. The compiler is
treating it as a word pointer. I even tried casting it to (rom int8 *) in
various places and it didn't help. You should email a bug report to CCS
support. I tested this in MPLAB simulator and put a breakpoint on the
delay_cycles(1) line, and looked at gfx_data and temp in a watch window.
Code:

#include <18F4620.h>
#fuses INTRC_IO,NOWDT,PUT,BROWNOUT,NOLVP
#use delay(clock=4M)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)

rom int8 scale[6]= {0x45,0x5A,0x41,0x42,0x43,0x44};

void draw_sprite (rom int8 *sprite_ptr)
{
int8 gfx_data;
int8 temp;

gfx_data = 0;
temp = 0;

gfx_data = *sprite_ptr;

delay_cycles(1);
}

//======================================
void main(void)
{
draw_sprite(scale);

while(1);
}
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