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Returning void

Started by Ironica Jul 16, 2003 at 9:07 AM 14 replies 1.2k views

Original Post

Jul 16, 2003 at 9:07 AM

Hmm... I just tryed this, and it seems to compile fine. Would it actually work as I'd expect?

void func(){
 return;
}

How about if I had something like:

void func(int v){
 if(v == 1)
  return;
 cout << v;
}

would that work fine? (I can't test it out right now.) I mean like print the number, unless it's equal to 1. If so, that's weird! I thought you couldn't return from a void function!

Crispy

170

Crispy

Jul 16, 2003 at 9:11 AM

That''s a perfectly valid piece of code. You can''t return a value from a function returning void.

Yanroy

Jul 16, 2003 at 9:11 AM

It works fine under MSVC 6. I do it all the time when I''m coding (largely because I''m a bad boy and I like to use void main() instead of int main()). I''ve never had a single problem with it. And it functions just like you''d expect with returning an actual value, except, obviously, nothing is returned

Maybe this isn''t ANSI compliant...

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Ironica

Author

Ironica

Jul 16, 2003 at 9:13 AM

quote:
Original post by Crispy
You can''t return a value from a function returning void.

Right. You can return from a void function, but you can''t return a value. Makes sense =)

Sneftel

297

Sneftel

Jul 16, 2003 at 9:16 AM

sure ya can. In fact, you can do this:


template<typename T> T func()
{
    return T();
}

Now, that''s not especially interesting, until you consider this:

func<void>();

Check it out! Not only are you returning from a void function, you are actually constructing and returning a variable of type void! Megacool!

JuNC

Jul 16, 2003 at 9:24 AM

Although that is a toy example, is void an actual value (i.e. the single value of type void) in C++ like, say, unit would be in ML? (just interested to know what the standard says about that)

Sneftel

297

Sneftel

Jul 16, 2003 at 9:33 AM

quote:
Original post by JuNC
Although that is a toy example, is void an actual value (i.e. the single value of type void) in C++ like, say, unit would be in ML? (just interested to know what the standard says about that)

Nope, it isn''t (except where it exists as void*). This feature is just to make templates a little more generic (I believe there''s a couple of STL helper classes that make use of it).

JuNC

Jul 16, 2003 at 9:35 AM

Actually, I just tested it with VC++6 & gcc 2.95.2

VC barfs, ''function returning void''

gcc no problem

Is gcc correct?

Sneftel

297

Sneftel

Jul 16, 2003 at 9:47 AM

Yep, gcc is correct. This is another one of those VC6 incompatibilities. I assume it''s fixed in .NET.

craphead

Jul 16, 2003 at 9:50 AM

gcc came first. 3.x sux stick with the old one. you cant use fsstream properly with 3.x.

JuNC

Jul 16, 2003 at 9:53 AM

/me rolls eyes - typical!

Oh well, I can't imagine I'll ever find it a problem

EDIT: I was replying to Sneftel, gcc 3.x rocks

[edited by - JuNC on July 16, 2003 11:15:24 AM]

Sneftel

297

Sneftel

Jul 16, 2003 at 9:59 AM

quote:
Original post by craphead
gcc came first. 3.x sux stick with the old one. you cant use fsstream properly with 3.x.

You''re not serious, are you? gcc 3.x has vastly better optimization. Perhaps your problems stem from the fact that there IS no "fsstream"?

Vich

Jul 16, 2003 at 11:14 AM

GCC 3.x fixed a problem over 2.9x (dunno what precisely) that was very crucial and took me weeks to find it out:

When I started a server application, and made a thread for every person that connected, I wanted to use ''string'' or a std list. Both crashed in version 2.9x and worked perfectly in 3.x

"My basic needs in life are food, love and a C++ compiler"
[Project AlterNova] [Novanet]

Ironica

Author

Ironica

Jul 16, 2003 at 1:29 PM

quote:
Original post by Sneftel
Yep, gcc is correct. This is another one of those VC6 incompatibilities. I assume it''s fixed in .NET.

I was using VC++.NET, so yes.

TSwitch

Jul 16, 2003 at 4:49 PM

quote:
Original post by Crispy
That's a perfectly valid piece of code. You can't return a value from a function returning void.

I did, once. But now there's a blue swirly vortex on the wall behind me and every now and then a person wearing some sort of alien space suit pokes his head through, says something about a parallel dimension and then that's when I fire off a couple shotgun shells in his direction. I got a piece of one, once, but someone dragged him back into the swirly dealie before I could get a knife to cut off his head and mount it on the wall.

[edited by - TSwitch on July 16, 2003 5:50:05 PM]

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