Default constructor in C

Question

Is there a way to have some kind of default constructor (like a C++ one) for C user types defined with a structure?

I already have a macro which works like a fast in

Answer 1

Following is a simple program that makes use of a constructor. Function "default_constructor" gets called inside main without any explicit function call.

#include        <stdio.h> 

void __attribute__ ((constructor)) default_constructor() 
{ 
    printf("%s\n", __FUNCTION__); 
} 

int main() 
{ 
    printf("%s\n",__FUNCTION__);
    return 0; 
}

Output: default_constructor main

Within the constructor function you can include some initialization statements and use the destructor function to free memory as follows,

#include    <stdio.h> 
#include    <stdlib.h>

struct somestruct
{
    int     empid;
    char *  name;
};

struct somestruct * str1;

void __attribute__ ((constructor)) a_constructor() 
{ 
    str1 = (struct somestruct *) malloc (sizeof(struct somestruct));
    str1 -> empid = 30228;
    str1 -> name = "Nandan";
} 

void __attribute__ ((destructor)) a_destructor()
{
    free(str1);
}

int main() 
{ 
    printf("ID = %d\nName = %s\n", str1 -> empid, str1 -> name);
    return 0;
}

Hope this will help you.