The route[x] pointers have to refer to properly allocated, writable memory.
In the code snippet provided they point into string literals ("message"), so what the code
effectively does is trying to modify that string (pseudo code, may or may not compile):
"message"[0] = 'M';
If "message" is allocated in flash (default), then assigning to it would work at runtime.
(Note that the ANSI C standard calls this "undefined behavior", meaning anything can happen, it can even work on some compilers. Just don't write into string literals...)
So if you want to be able to modify route[x][y], assign it to a buffer:
char buf[100000000];
route[0]= buf;
route[0][0] = 'H';
route[0][1] = '\0';
(or strcpy(route[0], "H")
Make sure buf is big enough for your string, it probably should not be 100000000 bytes though :smileywink:
I would suggest you search the web for articles describing how pointers and array work in C, I'm sure there are plenty of good references.
BTW: Be aware that on a HC08 the stack is limited. Allocating too huge buffers on the stack will cause strange effects when executing (stack overflow). Allocating too huge buffers globally will cause the linking step to fail.
Daniel
Hi....
I did the buff assigment with not a better response. Also I use malloc() to reserve memory. That works fime but changes to the entite ponter array is done, please check code above!
Thanks
#include <hidef.h> /* for EnableInterrupts macro */
#include "derivative.h" /* include peripheral declarations */
#include <stdlib.h>
#include <string.h>
void main(void) {
volatile char *route[5];
volatile char *y;
volatile char x[5];
char c, index;
SOPT_COPE = 0;
y = malloc(50 * sizeof(char)); // ALWAYS OK.
route[0] = malloc(50 * sizeof(char)); // ALWAYS OK.
route[1] = malloc(50 * sizeof(char)); // ALWAYS OK.
route[2] = malloc(50 * sizeof(char)); // ALWAYS OK.
route[3] = malloc(50 * sizeof(char)); // ALWAYS OK.
route[4] = malloc(50 * sizeof(char)); // ALWAYS OK.
route[0] = "This lines";
route[1] = "work";
route[2] = "fine if I";
route[3] = "assign them";
route[4] = "directly";
for (c = 0 ; c < 5 ; c++)
{
route[c] = "message ok";
}
//*********************************************************************************
x[0]= 'F';
x[1]= 'R';
x[2]= 'E';
x[3]= 'E';
x[4]= '\0';
y = x;
route[0] = y;
x[0]= 'f'; //After this line route[0][0] changes 'F' to 'f'
x[1]= 'r'; //After this line route[0][1] changes 'R' to 'r'
x[2]= 'e'; //After this line route[0][2] changes 'E' to 'e'
x[3]= 'e'; //After this line route[0][3] changes 'E' to 'e'
x[4]= '\0';
y = x;
route[1] = y;
x[0]= 's'; //After this line route[0][0] and route[1][0] changes 'f' to 's'
x[1]= 'c'; //After this line route[0][1] and route[1][1] changes 'r' to 'c'
x[2]= 'a'; //After this line route[0][2] and route[1][2] changes 'e' to 'a'
x[3]= 'l'; //After this line route[0][3] and route[1][3] changes 'e' to 'l'
x[4]= '\0';
y = x;
route[2] = y;
//*********************************************************************************
x[0]= 'F'; //After this line route[0][0] and route[1][0] changes 's' to 'F'
x[1]= 'R'; //After this line route[0][1] and route[1][1] changes 'c' to 'R'
x[2]= 'E'; //After this line route[0][2] and route[1][2] changes 'a' to 'E'
x[3]= 'E'; //After this line route[0][3] and route[1][3] changes 'l' to 'E'
x[4]= '\0';
(void) strcpy(y,x);
route[0] = y;
x[0]= 'f'; //After this line route[0][0] and route[1][0] changes 'F' to 'f'
x[1]= 'r'; //After this line route[0][1] and route[1][1] changes 'R' to 'r'
x[2]= 'e'; //After this line route[0][2] and route[1][2] changes 'E' to 'e'
x[3]= 'e'; //After this line route[0][3] and route[1][3] changes 'E' to 'e'
x[4]= '\0';
(void) strcpy(y,x);
route[1] = y;
x[0]= 's'; //After this line route[0][0] and route[1][0] changes 'f' to 's'
x[1]= 'c'; //After this line route[0][1] and route[1][1] changes 'r' to 'c'
x[2]= 'a'; //After this line route[0][2] and route[1][2] changes 'e' to 'a'
x[3]= 'l'; //After this line route[0][3] and route[1][3] changes 'e' to 'l'
x[4]= '\0';
(void) strcpy(y,x);
route[2] = y;
//*********************************************************************************
x[0]= 'F'; //After this line route[0][0] and route[1][0] changes 's' to 'F'
x[1]= 'R'; //After this line route[0][1] and route[1][1] changes 'c' to 'R'
x[2]= 'E';
x[3]= 'E';
x[4]= '\0';
*y = *x;
*(y+1) = *(x+1);
*(y+2) = *(x+2);
*(y+3) = *(x+3);
*(y+4) = *(x+4);
route[0] = y;
x[0]= 'f'; //After this line route[0][0] changes 'F' to 'f'
x[1]= 'r'; //After this line route[0][1] changes 'R' to 'r'
x[2]= 'e'; //After this line route[0][2] changes 'E' to 'e'
x[3]= 'e'; //After this line route[0][3] changes 'E' to 'e'
x[4]= '\0';
*y = *x;
*(y+1) = *(x+1);
*(y+2) = *(x+2);
*(y+3) = *(x+3);
*(y+4) = *(x+4);
route[1] = y;
x[0]= 's'; //After this line route[0][0] and route[1][0] changes 'f' to 's'
x[1]= 'c'; //After this line route[0][1] and route[1][1] changes 'r' to 'c'
x[2]= 'a'; //After this line route[0][2] and route[1][2] changes 'e' to 'a'
x[3]= 'l'; //After this line route[0][3] and route[1][3] changes 'e' to 'l'
x[4]= '\0';
*y = *x;
*(y+1) = *(x+1);
*(y+2) = *(x+2);
*(y+3) = *(x+3);
*(y+4) = *(x+4);
route[2] = y;
//*********************************************************************************
y= "FREE";
for (index = 0 ; index < 4; index ++)
{
route[1][index] = y[index]; // No change
x [index] = y[index];
}
x[index] = '\0';
y= "free";
for (index = 0 ; index < 4; index ++)
{
*(route[2] + index) = y[index]; // No change
*(x + index) = y[index];
}
x[index] = '\0';
y= "scal";
for (index = 0 ; index < 4; index ++)
{
*(route[3] + index) = *(y + index); // No change
*(x + index) = *(y + index);
}
x[index] = '\0';
for(; {
}
}
