Null pointer naming

This is a discussion on Null pointer naming within the C++ Programming forums, part of the General Programming Boards category; The question is whether foo(void); could ever be considered to be a function declaration, as it appears Prelude is suggesting ...

  1. #16
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    The question is whether foo(void); could ever be considered to be a function declaration, as it appears Prelude is suggesting it could be. In order for it to be ambiguous when void means null, it would have to have a legitimate meaning now when void doesn't mean null. That would be why you might test it on your compiler.

    As it is, I'm not sure that it is valid syntax, now. Perhaps Prelude can explain the ambiguity she believes would arise.

  2. #17
    semi-colon generator ChaosEngine's Avatar
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    Quote Originally Posted by Daved
    The question is whether foo(void); could ever be considered to be a function declaration, as it appears Prelude is suggesting it could be. In order for it to be ambiguous when void means null, it would have to have a legitimate meaning now when void doesn't mean null. That would be why you might test it on your compiler.

    As it is, I'm not sure that it is valid syntax, now. Perhaps Prelude can explain the ambiguity she believes would arise.
    while I agree that it wouldn't necessarily cause compiler-level ambiguity, I think naming the null pointer void would cause immense confusion.

    Besides they are 2 semantically different concepts.
    void indicates lack of type.
    nullptr indicates that a pointer points to a non-existant object (which usually has a type!)
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  3. #18
    (?<!re)tired Mario F.'s Avatar
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    void wouldn't mean null. Void would mean null pointer. That is at least the understanding I have of this dicussion at the light of the PDF file provided.

    In that context, foo(void) generates ambiguity. Isn't that so?

    If void meant null, then foo(void) would be an error if it was a declaration, but a perfectly valid syntax if it was a function call.
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  4. #19
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    >> I think naming the null pointer void would cause immense confusion.
    The original question was whether there is a technical reason for not using void. I do not know if there is one or not (perhaps Prelude's example is that reason).

    I do agree that it would cause confusion, and I certainly would prefer nullptr over void. However, you must consider that adding a keyword is not something that is done lightly, and any potentially adequate solution that avoids adding a keyword should be considered.

    My guess is that those working on this proposal have considered void and opted against it, and asking this question at comp.lang.c++.moderated would likely provide the best answer and explanation as to why. I also highly doubt that I would have much of a disagreement with whatever that explanation is.
    Last edited by Daved; 06-20-2006 at 05:59 PM.

  5. #20
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    Well there would be ambiguity if you did this:
    typeid(void);
    It is too clear and so it is hard to see.
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  6. #21
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    Well there would be ambiguity if you did this: typeid(void);
    "The null pointer cannot be used as the argument of a sizeof, typeid, or throw expression;" (from p. 2 of the pdf)

    The same would apply for your example. It would to ilegal as it is now.

    Code:
    int main() 
    {
      foo ( void );
    }
    If void meant null, then foo(void) would be an error if it was a declaration, but a perfectly valid syntax if it was a function call.
    Foo(void) cannot be a function declaration because
    a) C does not support nested funtions
    b) a function decleration would require a return value (possible void)

    I am very well aware of the ambiguous understanding of the keyword void this would introduce. But C can hardly be concidered a simple language as it is right now.

  7. #22
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    >a) C does not support nested funtions
    C and C++ both support function declarations within a function body. You're thinking of a function definition.

    >But C can hardly be concidered a simple language as it is right now.
    That's not an excuse for heaping even more complexity onto the language definition.
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  8. #23
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    #define zen void

    The null pointer shall point at nothing, and nothingness is the essence of zen, zen itself is thus pointing at null, and so, the circle of of code is complete. Know this, and know, that void ptr is the zen of C and C++.

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