Accessing a global variable when there is a local variable in the same name

[Mohanasundaram]

int i = 10;
int main()
{
int i = 20;
return 0;
}

Hi All,

I want to access the global variable i inside the main. Is there
a way to do this in C?

Regards,
Mohan.

[Martin Ambuhl]

Re: Accessing a global variable when there is a local variable inthe same name

Mohanasundaram wrote:
[color=blue]
> int i = 10;
> int main()
> {
> int i = 20;
> return 0;
> }
>
> Hi All,
>
> I want to access the global variable i inside the main. Is there
> a way to do this in C?[/color]

By not masking it with a redeclaration inside main.

[James Hu]

Re: Accessing a global variable when there is a local variable in the same name

On 2004-06-25, Mohanasundaram <mohanasundaram @msn.com> wrote:[color=blue]
> int i = 10;
> int main()
> {
> int i = 20;
> return 0;
> }
>
> I want to access the global variable i inside the main. Is there
> a way to do this in C?
>[/color]

int i = 10;
int main(void)
{
int *global_i_point er = &i;
int i = 20;

/* ... use global_i_pointe r to access the global variable i
from inside main ... */

return 0;
}

-- James

[Chris Dollin]

Re: Accessing a global variable when there is a local variable in the same name

Mohanasundaram wrote:
[color=blue]
> int i = 10;
> int main()
> {
> int i = 20;
> return 0;
> }
>
> Hi All,
>
> I want to access the global variable i inside the main. Is there
> a way to do this in C?[/color]

There's the easy way and the smartarse way.

The easy way is to rename the local i to something else, or to rename
the global i to something more sensible (a global variable called "i"
is probably a very bad idea).

The smararse way involves using pointers or nested extern declarations.
I'm not going to tell you the details. Just rename one or both i's.

--
Chris "electric hedgehog" Dollin
C FAQs at: http://www.faqs.org/faqs/by-newsgrou...mp.lang.c.html
C welcome: http://www.angelfire.com/ms3/bchambl...me_to_clc.html

[Vijay Kumar R Zanvar]

Re: Accessing a global variable when there is a local variable in the same name


"Mohanasundaram " <mohanasundaram @msn.com> wrote in message news:9bb9619e.0 406242156.73cf7 e4@posting.goog le.com...[color=blue]
> int i = 10;
> int main()
> {
> int i = 20;
> return 0;
> }
>
> Hi All,
>
> I want to access the global variable i inside the main. Is there
> a way to do this in C?
>
> Regards,
> Mohan.[/color]

int i = 10;
int main(void)
{
int i = 5;
{
extern int i;
i; /* the expression i will evaluate to 10 */
}
return 0;
}

--
Vijay Kumar R Zanvar
My Home Page - http://www.geocities.com/vijoeyz/

[CBFalconer]

Re: Accessing a global variable when there is a local variable in thesame name

Chris Dollin wrote:[color=blue]
> Mohanasundaram wrote:
>[color=green]
>> int i = 10;
>> int main()
>> {
>> int i = 20;
>> return 0;
>> }
>>
>> I want to access the global variable i inside the main. Is there
>> a way to do this in C?[/color]
>
> There's the easy way and the smartarse way.[/color]
.... snip ...

Around here, for a question like this, only the smartarse way is
acceptable.

--
Chuck F (cbfalconer@yah oo.com) (cbfalconer@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

[Dan Pop]

Re: Accessing a global variable when there is a local variable in the same name

In <9bb9619e.04062 42156.73cf7e4@p osting.google.c om> mohanasundaram@ msn.com (Mohanasundaram ) writes:
[color=blue]
>int i = 10;
>int main()
>{
> int i = 20;
> return 0;
>}
>
>Hi All,
>
> I want to access the global variable i inside the main. Is there
>a way to do this in C?[/color]

Explain why you can't rename one of the two variables.

If this is a homework question, try finding a better instructor. This
issue should NEVER arise in real C programs.

#include <stdio.h>

int i = 10;

int main()
{
int j = i;
int i = 20;
printf("%d\n", j);
return 0;
}

If the value of the global i might change during the execution of main(),
replace the definition of j by

int *p = &i;

but keep it still *before* the definition of the local i, and use *p any
time you need to access the global i.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

[Keith Thompson]

Re: Accessing a global variable when there is a local variable in the same name

CBFalconer <cbfalconer@yah oo.com> writes:[color=blue]
> Chris Dollin wrote:[color=green]
> > Mohanasundaram wrote:
> >[color=darkred]
> >> int i = 10;
> >> int main()
> >> {
> >> int i = 20;
> >> return 0;
> >> }
> >>
> >> I want to access the global variable i inside the main. Is there
> >> a way to do this in C?[/color]
> >
> > There's the easy way and the smartarse way.[/color]
> ... snip ...
>
> Around here, for a question like this, only the smartarse way is
> acceptable.[/color]

The obvious way, as others have mentioned, is to change the name of
the local variable. (Some languages have ways to refer directly to
variables in outer scopes using expanded names; C doesn't. I suspect
that's what the OP was really asking about.)

But the smartarse way, using a pointer, does illustrate what might
sometimes be a relevant point: just because a function doesn't have
direct visibility to a variable (either because it's hidden by a
declaration in an inner scope, or because it's a static variable
declared in another file or function), you can't necessarily assume
that the function can't read or modify the variable.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Emmanuel Delahaye]

Re: Accessing a global variable when there is a local variable in the same name

In 'comp.lang.c', James Hu <jxh@despammed. com> wrote:
[color=blue][color=green]
>> int i = 10;
>> int main()
>> {
>> int i = 20;
>> return 0;
>> }
>>
>> I want to access the global variable i inside the main. Is there
>> a way to do this in C?
>>[/color]
>
> int i = 10;
> int main(void)
> {
> int *global_i_point er = &i;
> int i = 20;
>
> /* ... use global_i_pointe r to access the global variable i
> from inside main ... */
>
> return 0;
> }[/color]

Clever. I'll try to keep it in mind.

--
-ed- get my email here: http://marreduspam.com/ad672570
The C-language FAQ: http://www.eskimo.com/~scs/C-faq/top.html
C-reference: http://www.dinkumware.com/manuals/reader.aspx?lib=c99
FAQ de f.c.l.c : http://www.isty-info.uvsq.fr/~rumeau/fclc/

[Keith Thompson]

Re: Accessing a global variable when there is a local variable in the same name

Dan.Pop@cern.ch (Dan Pop) writes:[color=blue]
> In <9bb9619e.04062 42156.73cf7e4@p osting.google.c om>
> mohanasundaram@ msn.com (Mohanasundaram ) writes:[color=green]
> >int i = 10;
> >int main()
> >{
> > int i = 20;
> > return 0;
> >}
> >
> >Hi All,
> >
> > I want to access the global variable i inside the main. Is there
> >a way to do this in C?[/color]
>
> Explain why you can't rename one of the two variables.
>
> If this is a homework question, try finding a better instructor. This
> issue should NEVER arise in real C programs.
>
> #include <stdio.h>
>
> int i = 10;
>
> int main()
> {
> int j = i;
> int i = 20;
> printf("%d\n", j);
> return 0;
> }
>
> If the value of the global i might change during the execution of main(),
> replace the definition of j by
>
> int *p = &i;
>
> but keep it still *before* the definition of the local i, and use *p any
> time you need to access the global i.[/color]

Yes, that will work. It will also create a potential headache for
future maintainers. Code that silently changes behavior when the
order of declarations is changed is not generally a good idea.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Dan Pop]

Re: Accessing a global variable when there is a local variable in the same name

In <lny8mb70uv.fsf @nuthaus.mib.or g> Keith Thompson <kst-u@mib.org> writes:
[color=blue]
>Dan.Pop@cern.c h (Dan Pop) writes:[color=green]
>> In <9bb9619e.04062 42156.73cf7e4@p osting.google.c om>
>> mohanasundaram@ msn.com (Mohanasundaram ) writes:[color=darkred]
>> >int i = 10;
>> >int main()
>> >{
>> > int i = 20;
>> > return 0;
>> >}
>> >
>> >Hi All,
>> >
>> > I want to access the global variable i inside the main. Is there
>> >a way to do this in C?[/color]
>>
>> Explain why you can't rename one of the two variables.
>>
>> If this is a homework question, try finding a better instructor. This[/color][/color]
^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^[color=blue][color=green]
>> issue should NEVER arise in real C programs.[/color][/color]
^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^[color=blue][color=green]
>>
>> #include <stdio.h>
>>
>> int i = 10;
>>
>> int main()
>> {
>> int j = i;
>> int i = 20;
>> printf("%d\n", j);
>> return 0;
>> }
>>
>> If the value of the global i might change during the execution of main(),
>> replace the definition of j by
>>
>> int *p = &i;
>>
>> but keep it still *before* the definition of the local i, and use *p any
>> time you need to access the global i.[/color]
>
>Yes, that will work. It will also create a potential headache for
>future maintainers. Code that silently changes behavior when the
>order of declarations is changed is not generally a good idea.[/color]

Which part of "This issue should NEVER arise in real C programs." was too
difficult for you to understand?

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

[Keith Thompson]

Re: Accessing a global variable when there is a local variable in the same name

Dan.Pop@cern.ch (Dan Pop) writes:[color=blue]
> In <lny8mb70uv.fsf @nuthaus.mib.or g> Keith Thompson <kst-u@mib.org> writes:[color=green]
> >Dan.Pop@cern.c h (Dan Pop) writes:[color=darkred]
> >> In <9bb9619e.04062 42156.73cf7e4@p osting.google.c om>
> >> mohanasundaram@ msn.com (Mohanasundaram ) writes:
> >> >int i = 10;
> >> >int main()
> >> >{
> >> > int i = 20;
> >> > return 0;
> >> >}
> >> >
> >> >Hi All,
> >> >
> >> > I want to access the global variable i inside the main. Is there
> >> >a way to do this in C?
> >>
> >> Explain why you can't rename one of the two variables.
> >>
> >> If this is a homework question, try finding a better instructor. This[/color][/color]
> ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^[color=green][color=darkred]
> >> issue should NEVER arise in real C programs.[/color][/color]
> ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^[color=green][color=darkred]
> >>
> >> #include <stdio.h>
> >>
> >> int i = 10;
> >>
> >> int main()
> >> {
> >> int j = i;
> >> int i = 20;
> >> printf("%d\n", j);
> >> return 0;
> >> }
> >>
> >> If the value of the global i might change during the execution of main(),
> >> replace the definition of j by
> >>
> >> int *p = &i;
> >>
> >> but keep it still *before* the definition of the local i, and use *p any
> >> time you need to access the global i.[/color]
> >
> >Yes, that will work. It will also create a potential headache for
> >future maintainers. Code that silently changes behavior when the
> >order of declarations is changed is not generally a good idea.[/color]
>
> Which part of "This issue should NEVER arise in real C programs." was too
> difficult for you to understand?[/color]

I understood it quite well, and I agree with it.

You declared that "This issue should NEVER arise in real C programs."
You could have stopped there, but you chose to present a solution.
That's fine. I commented on your solution. I agreed that it would
work, and raised another point that supports your contention that
"This issue should NEVER arise in real C programs."

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Dan Pop]

Re: Accessing a global variable when there is a local variable in the same name

In <lnlli77bm3.fsf @nuthaus.mib.or g> Keith Thompson <kst-u@mib.org> writes:
[color=blue]
>Dan.Pop@cern.c h (Dan Pop) writes:[color=green]
>> In <lny8mb70uv.fsf @nuthaus.mib.or g> Keith Thompson <kst-u@mib.org> writes:[color=darkred]
>> >Dan.Pop@cern.c h (Dan Pop) writes:
>> >> In <9bb9619e.04062 42156.73cf7e4@p osting.google.c om>
>> >> mohanasundaram@ msn.com (Mohanasundaram ) writes:
>> >> >int i = 10;
>> >> >int main()
>> >> >{
>> >> > int i = 20;
>> >> > return 0;
>> >> >}
>> >> >
>> >> >Hi All,
>> >> >
>> >> > I want to access the global variable i inside the main. Is there
>> >> >a way to do this in C?
>> >>
>> >> Explain why you can't rename one of the two variables.
>> >>
>> >> If this is a homework question, try finding a better instructor. This[/color]
>> ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^[color=darkred]
>> >> issue should NEVER arise in real C programs.[/color]
>> ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^[color=darkred]
>> >>
>> >> #include <stdio.h>
>> >>
>> >> int i = 10;
>> >>
>> >> int main()
>> >> {
>> >> int j = i;
>> >> int i = 20;
>> >> printf("%d\n", j);
>> >> return 0;
>> >> }
>> >>
>> >> If the value of the global i might change during the execution of main(),
>> >> replace the definition of j by
>> >>
>> >> int *p = &i;
>> >>
>> >> but keep it still *before* the definition of the local i, and use *p any
>> >> time you need to access the global i.
>> >
>> >Yes, that will work. It will also create a potential headache for
>> >future maintainers. Code that silently changes behavior when the
>> >order of declarations is changed is not generally a good idea.[/color]
>>
>> Which part of "This issue should NEVER arise in real C programs." was too
>> difficult for you to understand?[/color]
>
>I understood it quite well, and I agree with it.
>
>You declared that "This issue should NEVER arise in real C programs."
>You could have stopped there, but you chose to present a solution.[/color]

A solution to a *homework question*, which you arbitrarily chose to treat
as advice about how to write real C programs, otherwise your comment about
future maintainers would be downright idiotic: homework answers have no
future maintainers.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

[Keith Thompson]

Re: Accessing a global variable when there is a local variable in the same name

Dan.Pop@cern.ch (Dan Pop) writes:[color=blue]
> In <lnlli77bm3.fsf @nuthaus.mib.or g> Keith Thompson <kst-u@mib.org> writes:[/color]
[snip][color=blue][color=green]
> >I understood it quite well, and I agree with it.
> >
> >You declared that "This issue should NEVER arise in real C programs."
> >You could have stopped there, but you chose to present a solution.[/color]
>
> A solution to a *homework question*, which you arbitrarily chose to treat
> as advice about how to write real C programs, otherwise your comment about
> future maintainers would be downright idiotic: homework answers have no
> future maintainers.[/color]

Who said it was a homework question? The OP didn't say so. It's
entirely possible that it was homework; it's also possible that the OP
was trying to find out whether C has some kind of scope resolution
mechanism, as some other languages do.

I didn't treat your solution as advice about how to write real C
programs, but others might. In any case, I was simply expanding on
what you wrote. I don't know why you have a problem with that.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Dan Pop]

Re: Accessing a global variable when there is a local variable in the same name

In <lnlli6cnfz.fsf @nuthaus.mib.or g> Keith Thompson <kst-u@mib.org> writes:
[color=blue]
>Dan.Pop@cern.c h (Dan Pop) writes:[color=green]
>> In <lnlli77bm3.fsf @nuthaus.mib.or g> Keith Thompson <kst-u@mib.org> writes:[/color]
>[snip][color=green][color=darkred]
>> >I understood it quite well, and I agree with it.
>> >
>> >You declared that "This issue should NEVER arise in real C programs."
>> >You could have stopped there, but you chose to present a solution.[/color]
>>
>> A solution to a *homework question*, which you arbitrarily chose to treat
>> as advice about how to write real C programs, otherwise your comment about
>> future maintainers would be downright idiotic: homework answers have no
>> future maintainers.[/color]
>
>Who said it was a homework question? The OP didn't say so. It's
>entirely possible that it was homework;[/color]

My own text, prefacing the actual code, made it crystal clear that it was
supposed to be the answer to a stupid homework question and NOT used in
real life C code:

Explain why you can't rename one of the two variables.

If this is a homework question, try finding a better instructor. This
issue should NEVER arise in real C programs.
[color=blue]
>it's also possible that the OP
>was trying to find out whether C has some kind of scope resolution
>mechanism, as some other languages do.[/color]

And the answer is that it does (as shown in the various posted examples),
but it's better left unused.
[color=blue]
>I didn't treat your solution as advice about how to write real C
>programs, but others might.[/color]

Why? Was my disclaimer clear enough for you, but not for others?
[color=blue]
>In any case, I was simply expanding on
>what you wrote. I don't know why you have a problem with that.[/color]

Because I hate idiotic expansions on what I write. As I have already
explained, it makes no sense to invoke the future maintainers of something
that is *explicitly* presented as "not to be done in real C programs".

Without my explicit warning, your expansions would have been perfectly
sensible.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de