Output undefined?

[no]

main()
{
int i;
printf("%d %d",i++,++i);
}

Is the output undefined?

int main #include crap etc. is understood.

 

[Nils Petter Vaskinn]

int i;
printf("%d %d",i++,++i);

Is the output undefined?

Yes because you have never given i a value.

And that's before considering in which order i++ and ++i will be evaluated.

 

[Richard Bos]

Yes because you have never given i a value.

And that's before considering in which order i++ and ++i will be evaluated.

Order is immaterial; the mere occurence of them both together between
sequence points invokes undefined behaviour.

If either of you had read the FAQ, you'd have known this:
<http://www.eskimo.com/~scs/C-faq/q3.2.html>.

Richard

 

[Dan Pop]

Read the FAQ!

Yes because you have never given i a value.

And that's before considering in which order i++ and ++i will be evaluated.

The evaluation order does NOT matter. What matters is the lack of a
sequence point between these two expressions. So, instead of having an
unspecified output (assuming a properly initialised i) we have undefined
behaviour for the whole program. The FAQ clearly explains these issues!

Dan

 

[Jack Klein]

main()
{
int i;
printf("%d %d",i++,++i);
}

Is the output undefined?

int main #include crap etc. is understood.

Yes, even if you initialized I with a value. There is no sequence
point in the evaluation of arguments to functions, so your code
modifies i twice without an intervening sequence point.

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.learn.c-c++ ftp://snurse-l.org/pub/acllc-c++/faq

 

[Default User]

int main #include crap etc. is understood.

It would have taken less typing to just to do it right in the first
place.



Brian Rodenborn

 

[Joona I Palaste]

It would have taken less typing to just to do it right in the first
place.

I agree. I detect a shade of DAISNAID. Oh, sorry, forgot that
abbreviations are frowned upon here. "Do As I Say, Not As I Do".

--
/-- Joona Palaste ([email protected]) ---------------------------\
| Kingpriest of "The Flying Lemon Tree" G++ FR FW+ M- #108 D+ ADA N+++|
| http://www.helsinki.fi/~palaste W++ B OP+ |
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