Another strange linux kernel change

[Man-wai Chang to The Door (24000bps)]

i++ --> ++i, on a separate line! Does it matter?

http://www.kernel.org/diff/diffview.cgi?file=/pub/linux/kernel/v2.6/incr/patch-2.6.32.6-7.bz2;z=69


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/ v \ Simplicity is Beauty! May the Force and Farce be with you!
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[Victor Bazarov]

i++ --> ++i, on a separate line! Does it matter?

Do you mean to tell us that you don't know the difference between
pre-increment and post-increment?

V

 

[Vladimir Jovic]

i++ --> ++i, on a separate line! Does it matter?

No.

If it was like this:
j = ++i + i ++;
then it would matter.

 

[Victor Bazarov]

No.

If it was like this:
j = ++i + i ++;
then it would matter.

Huh?

Are you saying that

j = i++;

and

j = ++i;

have the same effect?

V

 

[Daniel Giaimo]

i++ --> ++i, on a separate line! Does it matter?

http://www.kernel.org/diff/diffview.cgi?file=/pub/linux/kernel/v2.6/incr/patch-2.6.32.6-7.bz2;z=69

i++ increments i and returns the old value. ++i increments i and
returns the new value. So, for example, if i were 4 to begin with,
then before the change the code would cause i to become 5 and j to
become 4, and after the change the code would cause i to become 5
and j to become 5.

 

[Vladimir Jovic]

Huh?

Are you saying that

j = i++;

and

j = ++i;

have the same effect?

Yes, that's what I said (shame on me). Fortunately I do not have to
debug offset by 1 in the j

 

[Stefan Ram]

Yes, that's what I said (shame on me). Fortunately I do not have to
debug offset by 1 in the j

The OP said »on a separate line«, so that should be:
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
j =
i++
;

versus

j =
++i
;

(Of course, this is irrelevant, but the question was put in
this way.)

 

[Man-wai Chang to The Door (24000bps)]

If it was like this:

j = ++i + i ++;
then it would matter.

Then that person could submit change to that program again and again and
got paid as usual.

1. change from "j=++i" to "j=i++"
2. change from "j=i++" to "j=++i"
3. go to (1)

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
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[Man-wai Chang to The Door (24000bps)]

i++ increments i and returns the old value. ++i increments i and

returns the new value. So, for example, if i were 4 to begin with,
then before the change the code would cause i to become 5 and j to
become 4, and after the change the code would cause i to become 5
and j to become 5.

I understood pre- and post-increment. But that line does not really
affect anything critical.

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.32.7
^ ^ 18:37:01 up 2:43 0 users load average: 1.00 1.00 1.00
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[James Kanze]

I understood pre- and post-increment. But that line does not
really affect anything critical.

Then the correction should be to delete it completely. My
impression is that j *is* being used later, so the change does
change the observable behavior of the code. (If j is not used
later, of course, you can just remove the assignment
completely.)

 

[Daniel Giaimo]

I understood pre- and post-increment. But that line does not really
affect anything critical.

Maybe you know more about the pre-conditions satisfied when this
particular piece of code is run, but from reading just what you posted
j is used on the very next line, so I would assume it matters whether
it starts at i or i+1.

 

[Man-wai Chang to The Door (24000bps)]

Maybe you know more about the pre-conditions satisfied when this

particular piece of code is run, but from reading just what you posted
j is used on the very next line, so I would assume it matters whether
it starts at i or i+1.

If that line was critical, it should have caused a kernel error in the
very beginning...

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
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[tonydee]

If that line was critical, it should have caused a kernel error in the
very beginning...

Ummmm... if your idea of quality control is that anything that doesn't
immediately crash your kernel can't be too bad, then please don't
submit any code.... ;-P. - Tony

 

[Man-wai Chang to The Door (24000bps)]

Ummmm... if your idea of quality control is that anything that doesn't

immediately crash your kernel can't be too bad, then please don't
submit any code.... ;-P. - Tony

Not if that programmer did something wrong in the very beginning!

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
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[Jorgen Grahn]

i++ --> ++i, on a separate line! Does it matter?

Last time I checked, Linux was written in C. This is comp.lang.c++.

/Jorgen