exercise 3.9, C++ Primer 4/e

[arnuld]

hai all,

here is the code:

#include <iostream>
#include <string>

int main() {
std::string s;
std::cout << s[0] << std::endl;
}


now i know it is WRONG as "s" is an empty string (implicit
initialisation by the default constructor of string class from Std.
Lib.). what i want to know is, when i run this code onto my Debian box
"gcc 3.3.5" it outputs the following characters:

"^@"

what is that? some non-printable character from ASCII, i guess.

do we call this an undefined behaviour?

thanks

"arnuld"
www.arnuld.blogspot.com

 

[red floyd]

hai all,

here is the code:

#include <iostream>
#include <string>

int main() {
std::string s;
std::cout << s[0] << std::endl;
}


now i know it is WRONG as "s" is an empty string (implicit
initialisation by the default constructor of string class from Std.
Lib.). what i want to know is, when i run this code onto my Debian box
"gcc 3.3.5" it outputs the following characters:

"^@"

what is that? some non-printable character from ASCII, i guess.

do we call this an undefined behaviour?

Yes. Therefore, anything can happen. In this case, "anything" includes
working "as expected" (whatever that is), crashing your app, crashing
your computer, dialing up the pentagon and starting WWIII, or causing
your monitor to explode.

 

[arnuld]

Yes. Therefore, anything can happen. In this case, "anything" includes
working "as expected" (whatever that is), crashing your app, crashing
your computer, ok

dialing up the pentagon and starting WWIII,
WHAT!

or causing your monitor to explode.

are you really seriuos?

"arnuld"