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Is the following guaranteed safe?

void InitInt(int & SomeInt)
{
SomeInt=3;
return;
}

int main()
{
int MainInt; // not initialised!
InitInt(MainInt);
std::cout << MainInt << std::endl;
return 0;
}

The intent of the function is to initialise its parm, so why
bother initialising it first in main()? Unless, of course, it is not
safe. Is it safe?

Sincerely,

Gene Wirchenko

On Wed, 17 Dec 2003 18:18:33 GMT, Gene Wirchenko
<> wrote:

> Is the following guaranteed safe?

Oops! I forgot to
#include <iostream>

> void InitInt(int & SomeInt)
> {
> SomeInt=3;
> return;
> }
>
> int main()
> {
> int MainInt; // not initialised!
> InitInt(MainInt);
> std::cout << MainInt << std::endl;
> return 0;
> }
>
> The intent of the function is to initialise its parm, so why
>bother initialising it first in main()? Unless, of course, it is not
>safe. Is it safe?

Sincerely,

Gene Wirchenko

"Gene Wirchenko" <> schrieb im
Newsbeitrag news:...
> On Wed, 17 Dec 2003 18:18:33 GMT, Gene Wirchenko
> <> wrote:
>
> > Is the following guaranteed safe?
>
> Oops! I forgot to
> #include <iostream>
>
> > void InitInt(int & SomeInt)
> > {
> > SomeInt=3;
> > return;
> > }
> >
> > int main()
> > {
> > int MainInt; // not initialised!
> > InitInt(MainInt);
> > std::cout << MainInt << std::endl;
> > return 0;
> > }
> >
> > The intent of the function is to initialise its parm, so why
> >bother initialising it first in main()? Unless, of course, it is not
> >safe. Is it safe?

In principle it´s safe though the practice itself is arguable - why not
initialize at the point of declaration?
To see whether it makes sense you´d need to provide some more details of
your intention.

Chris

"Gene Wirchenko" <> a écrit dans le
message de news: ...
> On Wed, 17 Dec 2003 18:18:33 GMT, Gene Wirchenko
> <> wrote:
>
> > Is the following guaranteed safe?
>
> Oops! I forgot to
> #include <iostream>
>
> > void InitInt(int & SomeInt)
> > {
> > SomeInt=3;
> > return;
> > }
> >
> > int main()
> > {
> > int MainInt; // not initialised!
> > InitInt(MainInt);
> > std::cout << MainInt << std::endl;
> > return 0;
> > }
> >
> > The intent of the function is to initialise its parm, so why
> >bother initialising it first in main()? Unless, of course, it is not
> >safe. Is it safe?
>
> Sincerely,
>
> Gene Wirchenko
>

sounds perfectly safe to me... nevertheless, I hardly understatnd the point
of this function : costs a function call and does almost nothing
interesting... and you don't need the return in the function InitInt.

On Wed, 17 Dec 2003 18:18:33 GMT, Gene Wirchenko
<> wrote:

> Is the following guaranteed safe?
>
> void InitInt(int & SomeInt)
> {
> SomeInt=3;
> return;
> }
>
> int main()
> {
> int MainInt; // not initialised!
> InitInt(MainInt);
> std::cout << MainInt << std::endl;
> return 0;
> }
>
> The intent of the function is to initialise its parm, so why
>bother initialising it first in main()? Unless, of course, it is not
>safe. Is it safe?

Yes - you don't convert MainInt to an rvalue until after you've given
it a valid value.

Tom

C++ FAQ: http://www.parashift.com/c++-faq-lite/
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html

"Le Géant Vert" <_> wrote...
>
> "Gene Wirchenko" <> a écrit dans le
> message de news: ...
> > On Wed, 17 Dec 2003 18:18:33 GMT, Gene Wirchenko
> > <> wrote:
> >
> > > Is the following guaranteed safe?
> >
> > Oops! I forgot to
> > #include <iostream>
> >
> > > void InitInt(int & SomeInt)
> > > {
> > > SomeInt=3;
> > > return;
> > > }
> > >
> > > int main()
> > > {
> > > int MainInt; // not initialised!
> > > InitInt(MainInt);
> > > std::cout << MainInt << std::endl;
> > > return 0;
> > > }
> > >
> > > The intent of the function is to initialise its parm, so why
> > >bother initialising it first in main()? Unless, of course, it is not
> > >safe. Is it safe?
> >
> > Sincerely,
> >
> > Gene Wirchenko
> >
>
> sounds perfectly safe to me... nevertheless, I hardly understatnd the
point
> of this function : costs a function call and does almost nothing
> interesting... and you don't need the return in the function InitInt.

Gene probably provided the simple function just for illustration purposes.
The point is that if you pass an uninitialised object by reference, some
compilers complain (with a warning, of course), often such warning is not
necessarily founded. That's all.

Victor

On Wed, 17 Dec 2003 19:39:13 +0100, "Le Géant Vert"
<_> wrote:

[snip]

>sounds perfectly safe to me... nevertheless, I hardly understatnd the point
>of this function : costs a function call and does almost nothing
>interesting... and you don't need the return in the function InitInt.

Thank you. As to the nit:

Oh, come off it! I posted a small program that illustrated my
point. It is called an example. If the initialisation function had
included code to initialise a 79 TB structure, it would not have made
the point any better (and would probably have obscured it).

Sincerely,

Gene Wirchenko

On Wed, 17 Dec 2003 18:46:30 +0000, tom_usenet
<> wrote:

>On Wed, 17 Dec 2003 18:18:33 GMT, Gene Wirchenko
><> wrote:

[snip]

>> The intent of the function is to initialise its parm, so why
>>bother initialising it first in main()? Unless, of course, it is not
>>safe. Is it safe?
>
>Yes - you don't convert MainInt to an rvalue until after you've given
>it a valid value.

Thank you.

Yes, very deliberately so.

(I have encountered languages where this would not be safe.)

Sincerely,

Gene Wirchenko

Gene Wirchenko wrote:

> Is the following guaranteed safe?
>
> void InitInt(int & SomeInt) {
> SomeInt=3;
> return;
> }

This is poor programming practice. The following:

int InitInt(void) {
return 3;
}

would be much better.

>
> int main(int argc, char* argv[]) {
> int MainInt; // not initialized!
> InitInt(MainInt);

int MainInt = InitInt();

You should *always* try to avoid uninitialized variables.

> std::cout << MainInt << std::endl;
> return 0;
> }
>
> The intent of the function is to initialized its parm, so why
> bother initializing it first in main()? Unless, of course, it is not
> safe. Is it safe?

It is *dangerous* because the variable may be used uninitialized.
If not by you, then by some poor programmer who must maintain your code.
Good programming habits will help keep you out of trouble.

"Gene Wirchenko" <> wrote in message
news:...
> On Wed, 17 Dec 2003 19:39:13 +0100, "Le Géant Vert"
> <_> wrote:
>
> [snip]
>
> >sounds perfectly safe to me... nevertheless, I hardly understatnd the
point
> >of this function : costs a function call and does almost nothing
> >interesting... and you don't need the return in the function InitInt.
>
> Thank you. As to the nit:
>
> Oh, come off it! I posted a small program that illustrated my
> point. It is called an example.

Now I think you understand why I object when people post "answers" that are
off the topic of the original question. Interesting