How to loop through an array declared in the header file? - c

Question

I have declared my header file with a structure consisting of arrays. It looks like this:
#ifndef HEADER_H_
#define HEADER_H_
typedef struct{
uint32_t State[3];
}h_t;
#endif
The C file that accesses this header file looks as follows:
#include"Header.h"
#include<stdio.h>
#include <stdlib.h>
char* old_states[3];
old_states[0] ="ABC";
old_states[1] ="BAC";
old_states[2] ="AAC";
h_t var;
for(i=0; i<3;i++){
var.State[i] = old_states[i];
printf("\n The state is %s", var.State[i]);
}
I print the states out to check them. THey are:
The state is ABC
The state is BAC
The state is AAC
Now I want to loop through each var.State[n], like var.State[0], var.State[1], var.State[2] individually.
That is loop through var.State[0] ="ABC" so that I could access each of the letters(A,B,C) individually. Can somebody tell me how could I achieve this?

Answer 1

In your code, old_states[n]is of char *, a pointer. OTOH, var.State[i] is of type uint32_t and they are not same.
A pointer type maybe converted to an integer type, but the result is strictly implementation dependent. To take this further, as stated in C11, chapter §6.3.2.3,
If the result cannot be represented in the integer type, the behavior is undefined.
So, basically you should avoid doing this unless you really really know what you're doing.
Then, in case of
printf("\n The state is %s", var.State[i])
%s expects a char * (a pointer to the initial element of an array of character type, to be exact, and in case the precision is not specified, it should be null-terminated), but what you're passing is uint32_t. It is called undefined behaviour again, as per the above point.
Moral of the story: enable compiler warnings and pay heed to them.
Solution:
Preferable, change your structure member type from
uint32_t State[3];
to
char * State[3];
then, assign them as you're doing now and finally, for accessing all individual elements, you can do something like (pseudocode)
for(i=0; i<3;i++)
{
int len = strlen(var.State[i]);
for(j=0; j < len ;j++) printf("%c \t", var.State[i][j]);
printf("\n");
}

Answer 2

As you declared uint32_t State[3]; and printing it with %s specifier that creates problem.
You can declare State[3]; as a 2-D character array like this -
EDIT
char State[3][4];
And to store values -
for(i=0;i<3;i++)
{
memcpy(var.State[i],old_states[i],strlen(old_states[i]);
}
And access each character like this -
var.State[i][j]
To print each character
for(i=0;i<3;i++)
{
for(j=0;j<3;j++)
{
printf("%c",var.State[i][j]);
}
printf("\n");
}