opertor ++

[ravinder thakur]

hello guys,

I am apparently puzzled by a very simple piece of code. What should be
the value of x after this statement ?

int x = 10;
x = x++;

I expect the value to be 10(since this is postfix). However the value
turns out to be 11. Any idea whats happening ?

Thanks
xoxo

 

[red floyd]

hello guys,

I am apparently puzzled by a very simple piece of code. What should be
the value of x after this statement ?

int x = 10;
x = x++;

I expect the value to be 10(since this is postfix). However the value
turns out to be 11. Any idea whats happening ?

The behavior is undefined.

 

[Senggen Choi]

hello guys,

I am apparently puzzled by a very simple piece of code. What should be
the value of x after this statement ?

int x = 10;
x = x++;

I expect the value to be 10(since this is postfix). However the value
turns out to be 11. Any idea whats happening ?

Thanks
xoxo

You need another variable.

int y = x++;

then y should be 10 as you expected, and x equals 11.

 

[Guest]

I am apparently puzzled by a very simple piece of code. What should be
the value of x after this statement ?

int x = 10;
x = x++;

I expect the value to be 10(since this is postfix). However the value
turns out to be 11. Any idea whats happening ?

from the C FAQ
http://c-faq.com/
(and this is the same in C++)

FAQ 3.1 "Why doesn't this code: a = i++; work?"

 

[Helfer Thomas]

Your example is funny since different compilers give different results:
- g++ gives 11
- clang gives 10

However I can't tell you what the results shall be according to the
standard (du to the assignement I would expect 11...)

Sincerly,

Helfer Thomas


Le 17/05/2012 07:20, ravinder thakur a écrit :

 

[Juha Nieminen]

Your example is funny since different compilers give different results:
- g++ gives 11
- clang gives 10

Both are correct. (In fact, if they produced -7 and 50391, they would
have still been correct.)

However I can't tell you what the results shall be according to the
standard (du to the assignement I would expect 11...)

It's undefined behavior, so anything goes.

 

[Jorgen Grahn]

Le 17/05/2012 07:20, ravinder thakur a écrit :

Your example is funny since different compilers give different results:
- g++ gives 11
- clang gives 10

However I can't tell you what the results shall be according to the
standard (du to the assignement I would expect 11...)

gcc gives a warning "operation on 'x' may be undefined". That should
be a quite clear indication about what result you can expect, right?

Never run your compiler without enabling full warnings.

/Jorgen