Re: std::list pass by reference initialization error

From:
"Jim Langston" <tazmaster@rocketmail.com>
Newsgroups:
comp.lang.c++
Date:
Wed, 30 Apr 2008 18:32:50 -0700
Message-ID:
<b59Sj.799$sC6.416@newsfe07.lga>
utab wrote:

On Apr 30, 9:58 pm, "Ray D." <ray.delvecc...@gmail.com> wrote:

Hey all,

I'm trying to pass a list into a function to edit it but when I
compile using g++ I continue to get the following error:

maintainNeighbors.cpp:104: error: invalid initialization of non-const
reference of type 'std::list<HostID, std::allocator<HostID> >&' from
a temporary of type 'std::list<HostID, std::allocator<HostID> >*'

helpers.cpp:99: error: in passing argument 1 of `void
CheckIfNeighborsHaveSentHello(std::list<HostID,
std::allocator<HostID>

&)'


The function is shown below:

void CheckIfNeighborsHaveSentHello(std::list<struct HostID>
&Neighbors)
{
        std::list<struct HostID>::iterator it;
        std::list<struct HostID>::iterator LastIt;
        struct timeb TimeBuffer;
        ftime( &TimeBuffer );

        it=Neighbors.begin();
        while (it!=Neighbors.end())
        {
                int Del=0;
                if (TimeBuffer.time - it->LastHelloRec > 40)
                        Del=1;
                LastIt = it;
                ++it;
                if (Del==1)
                        Neighbors.erase(LastIt);
        }

}

And the objects contained in the list are shown below, along with how
it is defined and the function call itself:

struct HostID {
        char IP[16];
        int Port;
        int LastHelloRec;
        int LastHelloSent;

};

std::list<struct HostID> ActiveNeighbors;
CheckIfNeighborsHaveSentHello(&ActiveNeighbors);


Here is the problem, expecting a reference, not a pointer ...
Reference
in the parameter list becomes an alias for ActiveNeighbors, but you
are
passing the address of the list, which is the cause I guess...


In other words, try changing it to:
CheckIfNeighborsHaveSentHello(ActiveNeighbors);

References work on the instanct name, not the address of the instance.

My guess is that it has something to do with the iterator, but I've
been stuck on this for a while now and I figure a more experienced
person could guide me in the right direction. Thanks in advance for
any help!


--
Jim Langston
tazmaster@rocketmail.com

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