Re: Passing a reference to a value returned by a function

[Mihnea Balta <dark_lkml at mymail dot ro>]

Thanks, it works with the const qualifier.
My next question would have been about how much visualc's behavior respects 
the standard, thanks for answering that in advance ;)

On Tuesday 11 March 2003 18:16, Oliver Kullmann wrote:
> On Tue, Mar 11, 2003 at 05:56:34PM +0200, Mihnea Balta wrote:
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> > From: Mihnea Balta <dark_lkml at mymail dot ro>
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> > Date: Tue, 11 Mar 2003 17:56:34 +0200
> > Subject: Passing a reference to a value returned by a function
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> >
> > Hi.
> >
> > I have this piece of code (excuse the long function names, it's example
> > code
> >
> > :) ):
> >
> > #include <stdio.h>
> >
> > struct type_t{
> >     int a, b, c;
> > };
> >
> > type_t function_returning_struct(){
> >     type_t  a;
> >
> >     a.a = 1;
> >     return a;
> > }
> >
> > int function_taking_reference(type_t& a){
> >     if(a.a == 1)
> >         return 1;
> >     else
> >         return 0;
> > }
> >
> > int main(){
> >     printf("%d\n",
> > function_taking_reference(function_returning_struct())); return 1;
> > }
> >
> > I'm trying to port code written like this from visualc to gcc. I suppose
> > that visualc compiles the above piece of code because it creates a
> > temporary type_t that holds the return of function_returning_struct(),
> > and passes a reference to that to function_taking_reference(). However,
> > gcc 3.2.2 won't compile that kind of code.
> >
> > Is there any way to make gcc work with such code? I'm asking because it's
> > in a lot of places, and adding a temp var by hand to all the places where
> > this stuff occurs would be a pain.
> >
> > Thanks.
>
> Hi,
>
> I hope very much that there is no way to make gcc to work with such code,
> since it doesn't make sense to pass temporary values by reference, and the
> standards explicitely forbids it. But you don't have to add variables ---
> just add the const qualifier to the argument type of
> function_taking_reference, and you have perfectly legal C++ code. Doing so
> doesn't change your code, but just increases safety.
>
> Oliver
>
>
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