CODEWITHSUNDEEP
c
Ami
Ami

Reputation: 363

how to access pointer member of nested structure in c code from another file

Below is complete code

brief summary of my problem is below: I have one global structure as mentioned below in file1.c and its getting initialized with some value in file1.c by function"assign_value()" and now I am printing this value by function "print_value()" from file2.c.

Problem is that: its not printing proper value from file2.c on the other hand if I call "print_value()" from file1.c inside function "assign_value()" as mentioned below then it shows proper value.

Please suggest what I am missing, why I am not able to print proper value by calling print_value() function in file2.c

  file1.c

My_struct_one is nested structure containing another structure My_struct_two and my_struct_obj_global is global variable in file1.c

    //file1.c

    #include <stdio.h>

    #include "file1.h"

    typedef unsigned long int List;

    typedef struct
    {

     List* my_list;
    }My_struct_two;


     typedef struct
    {

     My_struct_two struct_two;
    }My_struct_one;


     My_struct_one struct_global;



      void assign_value()
     {
     List value=9;

     struct_global.struct_two.my_list = &value;
     print_value();
     }

    void print_value()
    {
    printf("inside print");
    printf("value=%u\n",*(struct_global.struct_two.my_list));
    }

file1.h //file.h

  #ifndef _file1_c

  #define _file1_c

  void print_value();
  void assign_value();

  #endif

file2.c #include 

  #include "file1.h"

  int main()

  {

  assign_value();

  print_value();

  return 0;

   }

OUTPUT: inside printvalue=9 inside printvalue=4195506

Mine doubt is why I cant access value from file2.c,

Upvotes: 1

Views: 200

Answers (1)

AlexP
AlexP

Reputation: 4430

  • value is a local variable in function assign_value(). It is created when the function is entered, and it is destroyed when the function returns.

  • In function print_value(), the value of struct_global.struct_two.my_list is a dangling pointer: its value is the address of a variable which does not exist any more.

  • Dereferencing the value of a dangling pointer is undefined behavior.

Upvotes: 1

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