Comments on: 7.4 — Passing arguments by address

By: Alex

Alex — Tue, 26 Aug 2008 03:19:13 +0000

I forgot to tell you to update the function prototype above main. If it doesn’t match the actual function, the compiler will be unhappy, as you’re seeing. Update the prototype to int *& instead of int * and you’ll be fine.

By: Pieter

Pieter — Wed, 20 Aug 2008 18:22:40 +0000

I can’t get your last code (with the reference to a pointer) to work.
The linker gives the following error :
1>main.obj : error LNK2019: unresolved external symbol “void __cdecl SetToSix(int *)” (?SetToSix@@YAXPAH@Z) referenced in function _main
1>D:\Users\Pieter\Documents\Visual Studio 2008\Projects\Test\Debug\Test.exe : fatal error LNK1120: 1 unresolved externals

However, I was thinking…
If you change pTempPtr = &nSix; to *pTempPtr = nSix; (so dereference it and then assign the value of nSix) it works as it should, except that it doesn’t change the address of pTempPtr, but rather the contents.

By: Alex

Alex — Fri, 11 Jul 2008 02:04:49 +0000

The perils of cut and paste on display. Thanks for the note, it’s fixed now.

By: el-mudo

el-mudo — Wed, 09 Jul 2008 15:34:05 +0000

Hi Alex, it’s me again
There is a small error in the last example in this page, you forgot to change the comments in the code, it’s writen like that:

// This only changes pTempPtr, not pPtr!

but, in fact, for that example, pPtr has its memory address changed together with pTempPtr since it’s a reference to it.

By: Learn C++ - » 7.3 — Passing arguments by reference

Learn C++ - » 7.3 — Passing arguments by reference — Tue, 29 Apr 2008 04:59:00 +0000

[...] 2007 Prev/Next Posts « 7.2 — Passing arguments by value | Home | 7.4 — Passing arguments by address » Tuesday, July 24th, 2007 at 6:06 [...]

By: Alex

Alex — Thu, 20 Mar 2008 15:26:46 +0000

You don’t need to do an explicit dereference when using the array index operator ([]) because the array index operator does an implicit dereference.

By: Tom

Tom — Thu, 20 Mar 2008 06:15:21 +0000

1. In your first example function, PrintArray, don’t you have to dereference the pnArray variable, like this??:


void PrintArray(int *pnArray, int nLength)
{
    for (int iii=0; iii < nLength; iii++)
        cout << *pnArray[iii] << endl;
}

2. Minor typo: “The next logical question is, â€œWhat if we want to be able to be able to change the address”

By: Jason

Jason — Thu, 20 Dec 2007 21:47:52 +0000

Awesome, I get it.

I’d just like to say, that all made me realize that communicating C++’s logic is an artform.

By: Alex

Alex — Thu, 20 Dec 2007 17:32:44 +0000

I beefed up this lesson significantly because some of the stuff mentioned in the comments here is pretty important.

By: Jason

Jason — Thu, 20 Dec 2007 08:30:32 +0000

Ok, the code below does act as your code does. So, what’s up with my:
char *array = “strings” code above?

void PrintArray(char *pnArray)
{
    pnArray[0] = ‘c’;

}  

int main()
{
  char anArray[2] = “a”;
  cout < < anArray[0] << endl;
  PrintArray(anArray);
  cout << anArray[0] << endl;
}
Output:
a
c

[ I think I answered this in my response above. Let me know if it isn't clear. -Alex ]