Odtnhj

Here's what I did:

#include <stdio.h>
#include <string.h>

int main() 

 char name = "longname";
 printf("Name = %s n",name);
 strcpy(name,"evenlongername");
 printf("Name = %s n",name);
 printf("size of the array is : %d",sizeof(name));
 return 0;

It works, but how? I thought that once memory is assigned to an array in a program, it is not possible to change it. But, the output of this program is:

Name = longname 
Name = evenlongername 
size of the array is 9

So the compiler affirms that the size of the array is still 9. How is it able to store the word 'evenlongername' which has a size of 15 bytes (including the string terminator)?

In this case, name is allocated to fit "longname", which is 9 bytes. When you copy "evenlongername" into it, you're writing outside of bounds of that array. It's undefined behavior to write outside of the bounds, this means it may or may not work. Some times, it'll work, other times you'll get seg fault, yet other times you'll get weird behavior.

So the compiler affirms that the size of the array is still 9. How is it able to store the word 'evenlongername' which has a size of 15 bytes(including the string terminator)?

You are using a dangerous function (see Bugs), strcpy, which blindly copies source string to destination buffer without knowing about its size; in your case of copying 15 bytes into a buffer with size 9 bytes, essentially you have overflown. Your program may work fine if the memory access is valid and it doesn't overwrite something important.

Because C is a lower-level programming language, a C char is "barebone" mapping of memory, and not a "smart" container like C++ std::vector which automatically manages its size for you as you dynamically add and remove elements. If you are still not clear about the philosophy of C in this, I'd recommend you read *YOU* are full of bullshit. Very classic and rewarding.

Using sizeof on a char array will return the size of the buffer, not the length of the null-terminated string in the buffer. If you use strcpy to try and overflow the array, and it just happens to work (it's still undefined behavior), sizeof is still going to report the size used at declaration. That never changes.

If what you're interested in is observing how the length of a string changes with different assignments:

1. Use an adequate buffer to store every string you're going to test.


2. Use the function strlen in <string.h> which will give you the actual length of the string, and not the length of your buffer, which, once declared, is constant.