(C language)why does this code fail to compile

[Linda8888]

TL;DR Summary

Is it because both the variables of MyStruct in HisStruct.h and HerStruct.h, and the variable of int in MyStruct.h have the same name: 'a'

[B]// MyStruct.h[/B]
typedef struct {
  int a;
  float b;
  char c;
} MyStruct;[B]// HisStruct.h[/B]
#include "MyStruct.h"

typedef struct {
  MyStruct a;
  int b;
} HisStruct;[B]// HerStruct.h[/B]
#include "MyStruct.h"

typedef struct {
  MyStruct a;
  float b;
} HerStruct;[B]// main.c[/B]
#include "HisStruct.h"
#include "HerStruct.h"

int main() {
  HisStruct foo;
  HerStruct bar;

  foo.a.a = 1;
  bar.a.a = 2;

  return 0;
}

[Code tags inserted by a Mentor]

 

[Filip Larsen]

Is it because both the variables of MyStruct in HisStruct.h and HerStruct.h, and the variable of int in MyStruct.h have the same name: 'a'

The code itself is fine, but there is another problem. Can you work out what happens in the start of main.c just after the includes? Do you know the standard practice for making header files?

 

[Linda8888]

does main.c forgets to include <stdio.h>?

 

[Filip Larsen]

does main.c forgets to include <stdio.h>?

No, that is not the problem.

An #include work by literally including the content of the given file at the point where the include is, meaning you will get same result if you put all the content yourself into one file (e.g. main.c). If you replace all includes with their respective content for your code snippet it should be more apparent what the problem is.

If the problem still escapes you then focus on how many times MyStruct.h gets included. Is it more than one? If so, why is that a problem? Are you aware of how to guard against the this include effect?

 

[berkeman]

Summary:: Is it because both the variables of MyStruct in HisStruct.h and HerStruct.h, and the variable of int in MyStruct.h have the same name: 'a'

[B]// MyStruct.h[/B]
typedef struct {
  int a;
  float b;
  char c;
} MyStruct;[B]// HisStruct.h[/B]
#include "MyStruct.h"

typedef struct {
  MyStruct a;
  int b;
} HisStruct;[B]// HerStruct.h[/B]
#include "MyStruct.h"

typedef struct {
  MyStruct a;
  float b;
} HerStruct;[B]// main.c[/B]
#include "HisStruct.h"
#include "HerStruct.h"

int main() {
  HisStruct foo;
  HerStruct bar;

  foo.a.a = 1;
  bar.a.a = 2;

  return 0;
}

[Code tags inserted by a Mentor]

Welcome to PF, Linda. Please enclose your code in code tags (we have done that for you in your original post). Do it like this (but without the spaces):

[ code ]
<your code goes here>
[ /code ]

 

[FactChecker]

This is a common problem with include header files. They may be included all over the place, but their contents must only be defined once. The solution is to surround the contents of the header file with something called an "include guard" in your header files:

[CODE lang="c" title="include guard code"]#ifndef MYSTRUCT_H
#define MYSTRUCT_H
... your MyStruct.h code
#endif /* MYSTRUCK_H */[/CODE]
It is standard to make MYSTRUCT_H all upper case and to put the comment on the endif line so you know what block of code is ending.
You should get used to doing this in all your header files.

 

[jtbell]

Hi Linda, just a friendly tip:

In general, when a program fails to compile or run, it's very helpful to tell us the exact error message(s) that you get.

 

[Linda8888]

Thank you all. I got it!