Question

I want to know how to use a typedef struct outside the file where it is located. I mean, I have this:

In a File called “rtc_i2c.c” I have ————————————

#include "rtc_i2c.h"

struct time_date_str
{
  char year;
  char month;
  char date;
  char day;

  char hour;
  char minute;
  char second;
};


int RTCGetTime(TimeDate *timdatstrptr)
{
  timdatstrptr -> second = 0x12;

  return 0;
}

Then in a file called “rtc_i2c.h” I have ——————————-

#ifndef RTC_I2C_H 
#define RTC_I2C_H 

typedef struct time_date_str TimeDate;

#endif

And in “main.c” I have ————————————————-

#include "rtc_i2c.h"

TimeBase *TimeDateData;

void main(void)
{
  char DateTimeASCII[20]; 

  RTCGetTime(TimeDateData);

  DateTimeASCII[0] = ????????
}

Then when I step in to my code I enter in to RTCGetTime and in a watch window I can see the “timdatstrptr -> second = 12” assignment executing correctly. But the problem is outside. The compiler generates an error if I put “TimeDateData –> second” in the space with ????????. So I don’t know how am I supposed to access the contents of my globally defined array through a pointer.

If I understood, the pointer declared as “TimeBase *TimeDateData” is pointing to my array and is accessed with the “–>” because is a pointer. Am I wrong? how does this work?

Can anyone help me please? Thanks!!

Answer 1

The compiler doesn’t know the details of the time_date_str. You have 2 choices:

• Move the struct time_date_str declaration into the header file
• Make a sort of “accessor” function in rtc_i2c.c

It all boils down to the question: should outside entities know details about this structure ?

There are other problems as well, including the fact that you’re passing an uninitialized pointer to RTCGetTime.