variable scope in for loop

[Wenjie]

Hello,
We had a code review with the argument of
whether "i" is out of scope as illustrated
below:
for (int i=0; i<2004; i++)
{
doSomething(i);
}

for (i=0; i<2004; i++)
{
doSomethingElse (i);
}

Is it correct according to C++ language?
VC++6.0 works fine with above code.
Thanks and best regards,
Wenjie

[Rob Williscroft]

Wenjie wrote in news:d2******** *************** ***@posting.goo gle.com:

We had a code review with the argument of
whether "i" is out of scope as illustrated
below:
for (int i=0; i<2004; i++)
{
doSomething(i);
}

for (i=0; i<2004; i++)
{
doSomethingElse (i);
}

Is it correct according to C++ language?
Nope,
VC++6.0 works fine with above code.

Its a well known defect with this compiler, so much so that MSVC 7.1
also behaves this way by default (it has 2 option's that can remove
the defect /Za and /Zc:forScope).
Rob.
--
http://www.victim-prime.dsl.pipex.com/

[Wagner Bruna]

Hello,

go****@yahoo.co m (Wenjie) wrote in message news:<d2******* *************** ****@posting.go ogle.com>...

We had a code review with the argument of
whether "i" is out of scope as illustrated
below:
for (int i=0; i<2004; i++)
{
doSomething(i);
}

for (i=0; i<2004; i++)
{
doSomethingElse (i);
}

Is it correct according to C++ language?
VC++6.0 works fine with above code.

No, it's not correct. The scope of i ends at the end of the first
loop.

If you need VC++6 portability, a good workaround IMHO is to enclosure
the loops inside artificial blocks:

{
for (int i=0; i<2004; i++) {
doSomething(i);
}
}

{
for (int i=0; i<2004; i++) {
doSomethingElse (i);
}
}

--
Wagner

[Dietmar Kuehl]

go****@yahoo.co m (Wenjie) wrote:

We had a code review with the argument of
whether "i" is out of scope as illustrated
below:
for (int i=0; i<2004; i++)
{
doSomething(i);
}

for (i=0; i<2004; i++)
{
doSomethingElse (i);
}

Is it correct according to C++ language?
No, it is not.
VC++6.0 works fine with above code.

Well, this compiler is not known for its standard conformance, is it? Try
one base on the EDG front-end or, better yet, verify things in the standard.
--
<mailto:di***** ******@yahoo.co m> <http://www.dietmar-kuehl.de/>
Phaidros eaSE - Easy Software Engineering: <http://www.phaidros.co m/>

[Rolf Magnus]

Wagner Bruna wrote:

Hello,

go****@yahoo.co m (Wenjie) wrote in message
news:<d2******* *************** ****@posting.go ogle.com>...

We had a code review with the argument of
whether "i" is out of scope as illustrated
below:
for (int i=0; i<2004; i++)
{
doSomething(i);
}

for (i=0; i<2004; i++)
{
doSomethingElse (i);
}

Is it correct according to C++ language?
VC++6.0 works fine with above code.

No, it's not correct. The scope of i ends at the end of the first
loop.

If you need VC++6 portability, a good workaround IMHO is to enclosure
the loops inside artificial blocks:

{
for (int i=0; i<2004; i++) {
doSomething(i);
}
}

{
for (int i=0; i<2004; i++) {
doSomethingElse (i);
}
}

IIRC, another, less intrusive workaround is to

#define for if(false); else for

[Ron Natalie]

"Wagner Bruna" <wb****@yahoo.c om> wrote in message news:54******** *************** ***@posting.goo gle.com...

If you need VC++6 portability, a good workaround IMHO is to enclosure
the loops inside artificial blocks:

What we do (and I know this is technically illegal, but if VC++ is going to
break the rules, we will too!):

#define for if(false);else for

It's in our master win32 config file right after disabling warning 4786!

[Pete Becker]

Rolf Magnus wrote:

Wagner Bruna wrote:

Hello,

go****@yahoo.co m (Wenjie) wrote in message
news:<d2******* *************** ****@posting.go ogle.com>...

We had a code review with the argument of
whether "i" is out of scope as illustrated
below:
for (int i=0; i<2004; i++)
{
doSomething(i);
}

for (i=0; i<2004; i++)
{
doSomethingElse (i);
}

Is it correct according to C++ language?
VC++6.0 works fine with above code.

No, it's not correct. The scope of i ends at the end of the first
loop.

If you need VC++6 portability, a good workaround IMHO is to enclosure
the loops inside artificial blocks:

{
for (int i=0; i<2004; i++) {
doSomething(i);
}
}

{
for (int i=0; i<2004; i++) {
doSomethingElse (i);
}
}

IIRC, another, less intrusive workaround is to

#define for if(false); else for

An even less intrusive workaround is to move the variable declaration
outside the loop:

int i;
for (i=0; i<2004; i++)
{
doSomething(i);
}

for (i=0; i<2004; i++)
{
doSomethingElse (i);
}

Look, ma, no macros.

--

Pete Becker
Dinkumware, Ltd. (http://www.dinkumware.com)

[Ron Natalie]

"Pete Becker" <pe********@acm .org> wrote in message news:3F******** *******@acm.org ...

#define for if(false); else for

An even less intrusive workaround is to move the variable declaration
outside the loop:

int i;

Actually, I find that MORE intrusive. You have to put sloppy coding
practices in your code to correct for defects in the compiler.

If you were going to do that (and eschew macros), it would be better to
rename the variable and keep it defined inside the loop.

[Pete Becker]

Ron Natalie wrote:

"Pete Becker" <pe********@acm .org> wrote in message news:3F******** *******@acm.org ...

#define for if(false); else for

An even less intrusive workaround is to move the variable declaration
outside the loop:

int i;

Actually, I find that MORE intrusive. You have to put sloppy coding
practices in your code to correct for defects in the compiler.

It's only sloppy if you treat it that way. But you often have to do
things you'd rather not in order to get around compiler limitations.

--

Pete Becker
Dinkumware, Ltd. (http://www.dinkumware.com)

[Jeff Schwab]

Pete Becker wrote:

Rolf Magnus wrote:

Wagner Bruna wrote:

Hello,

go****@yahoo .com (Wenjie) wrote in message
news:<d2**** *************** *******@posting .google.com>...

We had a code review with the argument of
whether "i" is out of scope as illustrated
below:
for (int i=0; i<2004; i++)
{
doSomething(i);
}

for (i=0; i<2004; i++)
{
doSomethingElse (i);
}

Is it correct according to C++ language?
VC++6.0 works fine with above code.

No, it's not correct. The scope of i ends at the end of the first
loop.

If you need VC++6 portability, a good workaround IMHO is to enclosure
the loops inside artificial blocks:

{
for (int i=0; i<2004; i++) {
doSomething(i);
}
}

{
for (int i=0; i<2004; i++) {
doSomethingElse (i);
}
}

IIRC, another, less intrusive workaround is to

#define for if(false); else for

An even less intrusive workaround is to move the variable declaration
outside the loop:

int i;
for (i=0; i<2004; i++)
{
doSomething(i);
}

for (i=0; i<2004; i++)
{
doSomethingElse (i);
}

Look, ma, no macros.

I certainly prefer your macroless approach, but why not initialize i
where it is defined, and save an assignment?

int i = 0;

for( ; i < 2004; ++i )
do_something( i );

for( i = 0; i < 2004; ++i )
do_something_el se( i );

In production code, I tend to prefer while-loops to for-loops anyway, so
it would look something like this:

int i = 0;

while( i < 2004 )
{
do_something( i );
++i
}

i = 0;

while( i < 2004 )
{
do_something_el se( i );
++i;
}

I know folks are religious about for-loops; please don't be offended if
I don't respond to criticisms about keeping loop control at the top of
the block. :)