Passing NULL to a pointer parameter

Here is an example:

Public:
double firstCall(void *a, int *b)
{
return internalCall(a, b, NULL, NULL)
}

double secondCall(void *a, int *b, void *c, int *d)
{
return internalCall(a, b, c, d)
}

Private:
double internalCall(void *a, int *b, void *c, int *d)
{
.....
if (NULL != c)
work with c and d
}

I want to call firstCall(...) and secondCall(...) randomaly about 500 times.

I tested this code and seems it works. Is it a good idea to pass NULL as shown above? If not, what would be a good way to get expected outcome? I am just trying to reduce duplicate codes and kind of afraid if that gives a memory or program problem.

I am new to c++ and wanted to make sure this does not create a problem. I would appreciate if someone help me out.

Quote:

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Originally Posted by DevFellow

Code:

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Public:
          double firstCall(void *a, int *b)
          {
              return internalCall(a, b, NULL, NULL)
          }
          ...

Private:
        double internalCall(void *a, int *b, void *c, int *d)
        {
              .....
              if (NULL != c)
                    work with c and d
          }

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... Is it a good idea to pass NULL as shown above?

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Why not?
You also could declare your internalCall as

Code:

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double internalCall(void *a, int *b, void *c = NULL, int *d = NULL);

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PS: please, use Code tags while posting code snippets!

Thanks VictorN

Your parameters can have any value including NULL. What you have to do is make sure you don't use NULL pointers to access objects. That would crash your application.

It's recommended to pass nullptr instead of NULL macro.

Quote:

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Originally Posted by TubularX

It's recommended to pass nullptr instead of NULL macro.

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nullptr in Visual C++? In native code? :confused:
Note that nullptr can be used in VS2005 and VS2008 only when compiled with /clr option which in not used for the most of the project types discussed of this Forum.

And nullptr should not be used for native code in VS2010. There is a __nullptr instead (Microsoft-specific keyword)

Quote:

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Originally Posted by VictorN

And nullptr should not be used for native code in VS2010. There is a __nullptr instead (Microsoft-specific keyword)

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Hmm... that is somewhat troublesome for native code that is intended to be portable though since nullptr is now a standard C++ keyword.

Quote:

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Originally Posted by laserlight

Hmm... that is somewhat troublesome for native code that is intended to be portable though since nullptr is now a standard C++ keyword.

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Well, I'm not a guru in the modern C++ features, but it is what and how I've understood it from MSDN:

Quote:

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The __nullptr keyword is a Microsoft-specific keyword that has the same meaning as nullptr, but applies to only native code. If you use nullptr with native C/C++ code and then compile with the /clr compiler option, the compiler cannot determine whether nullptr indicates a native or managed null pointer value. To make your intention clear to the compiler, use nullptr to specify a managed value or __nullptr to specify a native value.

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Quote:

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Originally Posted by VictorN

Well, I'm not a guru in the modern C++ features, but it is what and how I've understood it from MSDN:

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Yeah, I read that MSDN entry before coming to my conclusion. That said, reading it again, I think that the way out is to simply use nullptr, but take care not to compile with /clr, which makes sense in my scenario since the code is intended to also be compiled by say, g++. Of course, in that case, your objection to TubularX's suggestion no longer holds.

nullptr is only available from VS2010.