Thread: double pointer to a structure

hi,
I need to know how to deference a double pointer to a structure.

i have a structure like this.
insert

Code:

struct string1
{
   unsigned char line1[20];

   unsigned char line2[30];


}

Now there is a function that returns the pointer to this structure.

insert

Code:

struct string1 *linecount()
{
    struct string1 string_var;
    //I fill the structure elements and return the pointer
    return &string_var
  

}

now in my main function i pass this structure pointer to another function and try to get the values of the structure members.But it gives junk values.

insert

Code:

int main()
{
   struct string1 *string_var2;
   char temp;
   string_var2 = linecount();
   temp=string_var2->line1[0]; //Dereferncing works fine here.
   func2(string_var2)


}

void func2(struct string1 *num)
{

   //when i defernece the pointer iam getting junk values.
  char mychar;
   mychar=num->line1[0];

}

Please guide me why it happens and the way to solve it.

Regards,
Rohit

Code:

struct string1 *linecount()
{
    struct string1 string_var;
    //I fill the structure elements and return the pointer
    return &string_var;
  

}

You are returning a pointer to a local variable. I am surprised your compiler issued no warnings.

You allocated the first struct object on the stack in linecount() and func2() writes over that memory region.

how should i get access of that structure that i have filled in the first function.Do i have to make the structure global ?

Example:

Code:

int main()
{
   struct string1 *string_var2;
   char temp;
   string_var2 = linecount();
   temp=string_var2->line1[0]; //Dereferncing works fine here.
   func2(string_var2)
}

struct string1 *linecount()
{
    return malloc(sizeof struct string1);
}

void func2(struct string1 *num)
{
   //when i defernece the pointer iam getting junk values.
   char mychar;
   mychar=num->line1[0];
}