Why whole structure can not be compared in C yet it can be copied? In other words, Why comparison in below program does not work? It does not print string.
#include <stdio.h>
#include <string.h>
int main(void)
{
struct emp
{
char n[20];
int age;
};
struct emp e1={"David",23};
struct emp e2=e1;
if(e2 == e1)
{
printf("The structures are equal");
}
return(0);
}
struct elements are usually aligned to some boundary, and when you initialize a struct (especially one on the stack), anything in the bytes skipped by alignment will be uninitialized. Moreover, the contents of n past the end of the constant initializer are not initialized. struct comparison is defined as s1 == s2 doing memcmp(&s1, &s2, sizeof s1), whereas struct initialization may or may not copy the skipped bytes. If you want to reliably compare structs, you should explicitly compare their elements.
just an idea, would casting it to a type such as void * and then comparing work? I was thinking something like
struct emp e1 = { "David",23 };
struct emp e2 = e1;
if (*((void*)&e1) == *((void*)&e2))
{
/* pure evil? I think not :3*/
}