how this is evaluated ?

[sam]

int i=0;

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

output:
4 3 2 1

why is not
1 2 3 4

 

[Grumble]

int i=0;

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

Does this help?
http://www.eskimo.com/~scs/C-faq/s3.html

 

[Bruno Desthuilliers]

int i=0;

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

output:
4 3 2 1

why is not
1 2 3 4

[laotseu@localhost dev]$ gcc -Wall -ansi -pedantic -oorder order.c
order.c: In function `main':
order.c:6: warning: operation on `i' may be undefined
order.c:6: warning: operation on `i' may be undefined
order.c:6: warning: operation on `i' may be undefined

AFAIK, the evaluation order of a function's args is
implementation-dependant (at least this is what I read in my K&R2).

HTH
Bruno

 

[Al Bowers]

int i=0;

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

output:
4 3 2 1

why is not
1 2 3 4

This is answered in the faq question 3.2 at
http://www.eskimo.com/~scs/C-faq/q3.2.html

 

[Christopher Benson-Manica]

AFAIK, the evaluation order of a function's args is
implementation-dependant (at least this is what I read in my K&R2).

Or entirely undefined, as in this case.

 

[Dan Pop]

Or entirely undefined, as in this case.

It is actually unspecified. The undefined behaviour in this example is
not a consequence of the evaluation order being unspecified, it's a
consequence of the lack of sequence points between the evaluation of the
arguments (the standard allows parallel evaluation).

Dan

 

[Martin Ambuhl]

int i=0;

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

output:
4 3 2 1

why is not
1 2 3 4

Because it's not
42 42 42 42

Please check the FAQ before posting. Then you would know that your
question is old, tired, and more than adequately answered already -- in
countless threads started by other people as clueless as you, as well as in
the the FAQ.

 

[Christopher Benson-Manica]

Please check the FAQ before posting. Then you would know that your
question is old, tired, and more than adequately answered already -- in
countless threads started by other people as clueless as you, as well as in
the the FAQ.

^^^^^^^

Was was that intentional, or was it just a quirk quirk of the mind?

 

[E. Robert Tisdale]

Please check the FAQ before posting.
Then you would know that your question is old, tired
and more than adequately answered already --
in countless threads started by other people as clueless as you,
as well as in the the FAQ.

Please cite and quote the relevant FAQ.

 

[Kevin Goodsell]

AFAIK, the evaluation order of a function's args is
implementation-dependant (at least this is what I read in my K&R2).

Strictly speaking, order of argument evaluation is unspecified. This is
different from undefined and implementation-defined. Unspecified means
there is some set of options the implementation must choose from.
Undefined means the standard has nothing to say about it (so the
implementation can choose from potentially infinite options).
Implementation-defined means that the implementation must choose and
document the method it uses. As far as I know, argument evaluation order
need not be documented by the implementation, so while you may be able
to determine it experimentally, you can never be completely sure that it
doesn't use a different order in some circumstances.

-Kevin

 

[Peter Nilsson]

int i=0;

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

output:
4 3 2 1

why is not
1 2 3 4

[laotseu@localhost dev]$ gcc -Wall -ansi -pedantic -oorder order.c
order.c: In function `main':
order.c:6: warning: operation on `i' may be undefined
order.c:6: warning: operation on `i' may be undefined
order.c:6: warning: operation on `i' may be undefined

This is in the FAQ.

AFAIK, the evaluation order of a function's args is
implementation-dependant (at least this is what I read in my K&R2).

No, it's unspecified. Even implementations which require arguments to
be placed on a hardware stack in a specific order need not evaluate
argument expressions in that (or its reverse) order.

 

[Mark A. Odell]

The OP wrote:

int i=0;

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

output:
4 3 2 1

why is not
1 2 3 4

Please cite and quote the relevant FAQ.

http://www.eskimo.com/~scs/C-faq/q3.2.html

You think we make this stuff up E. Robert?

 

[Keith Thompson]

Please cite and quote the relevant FAQ.

I don't think the FAQ directly addresses order of evaluation of
function arguments or the lack of sequence points between them, but
question 3.2 comes close.

 

[CBFalconer]

.... snip ...


http://www.eskimo.com/~scs/C-faq/q3.2.html

You think we make this stuff up E. Robert?

I suggest you are better off ignoring Trollsdale unless he gives
his usual erroneous advice. The above is a pure troll, and won't
lead anyone astray.

 

[Dan Pop]

Please cite and quote the relevant FAQ.

Why?

 

[Mark A. Odell]

I suggest you are better off ignoring Trollsdale unless he gives
his usual erroneous advice. The above is a pure troll, and won't
lead anyone astray.

Good point. Boy, I hope he really doesn't work at jpl.nasa.gov, we don't
need anymore Mars space craft losses.