Question

I have a networking framework that I am writing (Trying to implement reliable layer over UDP). I have this receive function that accepts a pointer to a packet object. The network framework then does a whole load of stuff to receive a packet, and sets the value of the packet pointer to this packet. But this happens a few functions deep. So what I am essentially wondering is, why this doesn’t something like this work for me: (very basic example to show you what i mean)

void Main()
{
   int* intPointer = NULL;
   SomeFunction(intPointer);
   //intPointer is still null?
}
void SomeFunction(int* outInt)
{
   SomeOtherFunction(outInt);
}

void SomeOtherFunction(int* outInt)
{
   outInt = new int(5);
}

Answer 1

SomeOtherFunction is passed a pointer by value, so the assignment only changes the local copy of the passed address.

To make this work, pass the pointer by reference:

void Main()
{
   int* intPointer = NULL;
   SomeFunction(intPointer);
   //intPointer is still null?
}
void SomeFunction(int*& outInt)
{
   SomeOtherFunction(outInt);
}

void SomeOtherFunction(int*& outInt)
{
   outInt = new int(5);
}

Having said that, is there something wrong with using a return value?

void Main()
{
   int* intPointer = SomeFunction(intPointer);
   //intPointer is still null?
}
int* SomeFunction()
{
   return SomeOtherFunction();
}

int* SomeOtherFunction()
{
   return new int(5);
}

[ Update following comment. ]

Well, if you have a return value indicating the status, presumably indicating whether or not the integer has been read, then what you really want is (using bool as a placeholder for your specific status):

void Main()
{
   int intPointer = 0;
   if (SomeFunction(intPointer) == true)
   {
       // read something
   }
   else
   {
       // failed to read.
   }
}
bool SomeFunction(int& outInt)
{
   return SomeOtherFunction(outInt);
}

bool SomeOtherFunction(int& outInt)
{
   outInt = 5;
   return true;
}