Implementation-defined behaviour

[Ioannis Vranos]

AFAIK the following is implementation-defined behaviour, am I right?:


#include <stdio.h>


int main(void)
{
int n= 0;

printf("%d\n", n++);


return 0;
}

[santosh]

Re: Implementation-defined behaviour

Ioannis Vranos wrote:

AFAIK the following is implementation-defined behaviour, am I right?:
>
#include <stdio.h>
>
int main(void)
{
int n= 0;
printf("%d\n", n++);
return 0;
}

I don't think so.

[Ioannis Vranos]

Re: Implementation-defined behaviour

santosh wrote:

Ioannis Vranos wrote:
>

>AFAIK the following is implementation-defined behaviour, am I right?:
>>
>#include <stdio.h>
>>
>int main(void)
>{
>int n= 0;
>printf("%d\n ", n++);
>return 0;
>}

>
I don't think so.

There are similar examples at 2.12 of K&R2.


Two quotes from there:

"printf("%d %d\n", ++n, power(2, n)); /* WRONG */"


"One unhappy situation is typified by the statement

a[i]= i++;"

[Eric Sosman]

Re: Implementation-defined behaviour

Ioannis Vranos wrote:

AFAIK the following is implementation-defined behaviour, am I right?:
>
>
#include <stdio.h>
>
>
int main(void)
{
int n= 0;
>
printf("%d\n", n++);
>
>
return 0;
}

Only by quibbles: the form of "successful termination"
returned to the host environment is implementation-defined,
the actual new-line representation written to stdout in
response to the '\n' is implementation-defined, and things
of that sort.

What aspect do you believe is not Standard-defined?

--
Eric Sosman
esosman@ieee-dot-org.invalid

[Ioannis Vranos]

Re: Implementation-defined behaviour

Eric Sosman wrote:

Ioannis Vranos wrote:

>AFAIK the following is implementation-defined behaviour, am I right?:
>>
>>
>#include <stdio.h>
>>
>>
>int main(void)
>{
> int n= 0;
>>
> printf("%d\n", n++);
>>
>>
> return 0;
>}

>
Only by quibbles: the form of "successful termination"
returned to the host environment is implementation-defined,
the actual new-line representation written to stdout in
response to the '\n' is implementation-defined, and things
of that sort.
>
What aspect do you believe is not Standard-defined?

I am talking about the implementation-defined behaviour of the printf()
call described at 2.12 of K&R2.

[santosh]

Re: Implementation-defined behaviour

Ioannis Vranos wrote:

santosh wrote:

>Ioannis Vranos wrote:
>>

>>AFAIK the following is implementation-defined behaviour, am I
>>right?:
>>>
>>#include <stdio.h>
>>>
>>int main(void)
>>{
>>int n= 0;
>>printf("%d\n" , n++);
>>return 0;
>>}

>>
>I don't think so.

>
There are similar examples at 2.12 of K&R2.
>
>
Two quotes from there:
>
"printf("%d %d\n", ++n, power(2, n)); /* WRONG */"
>
>
"One unhappy situation is typified by the statement
>
a[i]= i++;"

Well these examples are different from what you have shown above. The
first example above invokes unspecified behaviour while the second one
invokes undefined behaviour. The example in your first post does
neither as far as I can see.

[Ian Collins]

Re: Implementation-defined behaviour

Ioannis Vranos wrote:

Eric Sosman wrote:

>Ioannis Vranos wrote:

>>AFAIK the following is implementation-defined behaviour, am I right?:
>>>
>>>
>>#include <stdio.h>
>>>
>>>
>>int main(void)
>>{
>> int n= 0;
>>>
>> printf("%d\n", n++);
>>>
>>>
>> return 0;
>>}

> Only by quibbles: the form of "successful termination"
>returned to the host environment is implementation-defined,
>the actual new-line representation written to stdout in
>response to the '\n' is implementation-defined, and things
>of that sort.
>>
> What aspect do you believe is not Standard-defined?

>
>
I am talking about the implementation-defined behaviour of the printf()
call described at 2.12 of K&R2.
>

There's nothing wrong with your example, the one you cite is completely
different. If you had tried to use n again in the printf, you would hit UB.

--
Ian Collins.

[Ioannis Vranos]

Re: Implementation-defined behaviour

Ian Collins wrote:

Ioannis Vranos wrote:

>Eric Sosman wrote:

>>Ioannis Vranos wrote:
>>>AFAIK the following is implementation-defined behaviour, am I right?:
>>>>
>>>>
>>>#include <stdio.h>
>>>>
>>>>
>>>int main(void)
>>>{
>>> int n= 0;
>>>>
>>> printf("%d\n", n++);
>>>>
>>>>
>>> return 0;
>>>}
>> Only by quibbles: the form of "successful termination"
>>returned to the host environment is implementation-defined,
>>the actual new-line representation written to stdout in
>>response to the '\n' is implementation-defined, and things
>>of that sort.
>>>
>> What aspect do you believe is not Standard-defined?

>>
>I am talking about the implementation-defined behaviour of the printf()
>call described at 2.12 of K&R2.
>>

There's nothing wrong with your example, the one you cite is completely
different. If you had tried to use n again in the printf, you would hit UB.

So, printf("%d "%d\n", x++, x++); invokes implementation-defined
behaviour, while printf("%d\n", x++); doesn't invoke
implementation-defined behaviour?

[Dann Corbit]

Re: Implementation-defined behaviour

"Ioannis Vranos" <ivranos@nospam .no.spamfreemai l.grwrote in message
news:fsho27$1o9 d$1@ulysses.noc .ntua.gr...

Ian Collins wrote:

>Ioannis Vranos wrote:

>>Eric Sosman wrote:
>>>Ioannis Vranos wrote:
>>>>AFAIK the following is implementation-defined behaviour, am I right?:
>>>>>
>>>>>
>>>>#include <stdio.h>
>>>>>
>>>>>
>>>>int main(void)
>>>>{
>>>> int n= 0;
>>>>>
>>>> printf("%d\n", n++);
>>>>>
>>>>>
>>>> return 0;
>>>>}
>>> Only by quibbles: the form of "successful termination"
>>>returned to the host environment is implementation-defined,
>>>the actual new-line representation written to stdout in
>>>response to the '\n' is implementation-defined, and things
>>>of that sort.
>>>>
>>> What aspect do you believe is not Standard-defined?
>>>
>>I am talking about the implementation-defined behaviour of the printf()
>>call described at 2.12 of K&R2.
>>>

>There's nothing wrong with your example, the one you cite is completely
>different. If you had tried to use n again in the printf, you would hit
>UB.

>
>
So, printf("%d %d\n", x++, x++); invokes implementation-defined

so does:
printf("%d %d\n", x++, x);

behaviour, while printf("%d\n", x++); doesn't invoke
implementation-defined behaviour?

This one does not.



--
Posted via a free Usenet account from http://www.teranews.com

[Andrey Tarasevich]

Re: Implementation-defined behaviour

Ioannis Vranos wrote:

So, printf("%d "%d\n", x++, x++); invokes implementation-defined
behaviour, while printf("%d\n", x++); doesn't invoke
implementation-defined behaviour?

'printf("%d "%d\n", x++, x++)' invokes _undefined_ behavior. 'printf("%d
"%d\n", x++, x)' also invokes _undefined_ behavior.

'printf("%d\n", x++)' does not invoke undefined behavior.

"Implementa tion-defined behavior" is not immediately relevant to the
nature of your question.

--
Best regards,
Andrey Tarasevich

[Barry Schwarz]

Re: Implementation-defined behaviour

On Fri, 28 Mar 2008 05:18:31 +0200, Ioannis Vranos
<ivranos@nospam .no.spamfreemai l.grwrote:

>Ian Collins wrote:

>Ioannis Vranos wrote:

>>Eric Sosman wrote:
>>>Ioannis Vranos wrote:
>>>>AFAIK the following is implementation-defined behaviour, am I right?:
>>>>>
>>>>>
>>>>#include <stdio.h>
>>>>>
>>>>>
>>>>int main(void)
>>>>{
>>>> int n= 0;
>>>>>
>>>> printf("%d\n", n++);
>>>>>
>>>>>
>>>> return 0;
>>>>}
>>> Only by quibbles: the form of "successful termination"
>>>returned to the host environment is implementation-defined,
>>>the actual new-line representation written to stdout in
>>>response to the '\n' is implementation-defined, and things
>>>of that sort.
>>>>
>>> What aspect do you believe is not Standard-defined?
>>>
>>I am talking about the implementation-defined behaviour of the printf()
>>call described at 2.12 of K&R2.
>>>

>There's nothing wrong with your example, the one you cite is completely
>different. If you had tried to use n again in the printf, you would hit UB.

>
>
>So, printf("%d "%d\n", x++, x++); invokes implementation-defined

This invokes undefined behavior. The commas separating function
arguments are not sequence points. You are modifying x twice without
an intervening sequence point.

>behaviour, while printf("%d\n", x++); doesn't invoke
>implementati on-defined behaviour?

Remove del for email

[Philip Potter]

Re: Implementation-defined behaviour

Ioannis Vranos wrote:

So, printf("%d "%d\n", x++, x++); invokes implementation-defined
behaviour, while printf("%d\n", x++); doesn't invoke
implementation-defined behaviour?
>

Aside from the fact that this won't compile (you have one too many "
characters), this is almost exactly the same question as FAQ 3.2. The
problem is not the individual 'x++' expressions, but the way they
interact with each other.

Philip

[Ioannis Vranos]

Re: Implementation-defined behaviour

Andrey Tarasevich wrote:

Ioannis Vranos wrote:

>So, printf("%d "%d\n", x++, x++); invokes implementation-defined
>behaviour, while printf("%d\n", x++); doesn't invoke
>implementati on-defined behaviour?

>
'printf("%d "%d\n", x++, x++)' invokes _undefined_ behavior. 'printf("%d
"%d\n", x++, x)' also invokes _undefined_ behavior.
>
'printf("%d\n", x++)' does not invoke undefined behavior.
>
"Implementa tion-defined behavior" is not immediately relevant to the
nature of your question.

K&R2 mentions the following:

"printf("%d %d\n", ++n, power(2,n)); /* WRONG */

can produce different results with different compilers, depending on
whether n is incremented before power is called".


That's why I call it implementation-defined behaviour.

[Eric Sosman]

Re: Implementation-defined behaviour

Ioannis Vranos wrote:

Eric Sosman wrote:

>Ioannis Vranos wrote:

>>AFAIK the following is implementation-defined behaviour, am I right?:

> [...]
> What aspect do you believe is not Standard-defined?

I am talking about the implementation-defined behaviour of the printf()
call described at 2.12 of K&R2.

Aha! This problem is explained on pages 366-7 of the
Frobozz Magic C version 42 Release Notes and Do-It-Yourself
Lobotomy Manual. Read it, and get back to me if there's
anything that's still unclear.

--
Eric Sosman
esosman@ieee-dot-org.invalid

[Richard Tobin]

Re: Implementation-defined behaviour

In article <kqidnUJehahkeH HanZ2dnUVZ_ramn Z2d@comcast.com >,
Eric Sosman <esosman@ieee-dot-org.invalidwrot e:

Aha! This problem is explained on pages 366-7 of the
>Frobozz Magic C version 42 Release Notes and Do-It-Yourself
>Lobotomy Manual.

I have a copy of the Encyclopedia Frobozzica on my bookshelf next to
K&R 2, but I've never seen the manual you mention. Is it still
available?

-- Richard

--
:wq