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Anyone else think it's kinda weird...

This is a discussion on Anyone else think it's kinda weird... within the General Discussions forums, part of the Community Boards category; ...how when some functions return 0, it was a success, yet when others return NULL, it's a failure?...

  1. #1
    Third Eye Babkockdood's Avatar
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    Anyone else think it's kinda weird...

    ...how when some functions return 0, it was a success, yet when others return NULL, it's a failure?
    Quote Originally Posted by The Jargon File
    Microsoft Windows - A thirty-two bit extension and graphical shell to a sixteen-bit patch to an eight-bit operating system originally coded for a four-bit microprocessor which was written by a two-bit company that can't stand one bit of competition.

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    (?<!re)tired Mario F.'s Avatar
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    err, no?

    Depends on exactly the functions you are talking about here. But null and 0 are two very distinct things. And even when used in a return value to denote failure, they still have a distinct semantics that is quite intentional.

    Care to give an example of what functions you are talking about. Are we discussing C here, per chance?
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

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    Third Eye Babkockdood's Avatar
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    Quote Originally Posted by Mario F. View Post
    err, no?

    Depends on exactly the functions you are talking about here. But null and 0 are two very distinct things. And even when used in a return value to denote failure, they still have a distinct semantics that is quite intentional.

    Care to give an example of what functions you are talking about. Are we discussing C here, per chance?
    Yeah, C. strcmp() and strncmp() return 0 if two strings are equal (success). And functions like malloc() and fopen() return NULL if there's not enough memory, or if the file couldn't be opened (failure). Last time I checked, NULL == 0. I thought that was pretty weird.
    Quote Originally Posted by The Jargon File
    Microsoft Windows - A thirty-two bit extension and graphical shell to a sixteen-bit patch to an eight-bit operating system originally coded for a four-bit microprocessor which was written by a two-bit company that can't stand one bit of competition.

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    (?<!re)tired Mario F.'s Avatar
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    I'll give you a few minutes to think why's that...

    Think of what the function is returning exactly and what is the use you make of what is returned.
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  5. #5
    Third Eye Babkockdood's Avatar
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    Never mind.

    :P
    Quote Originally Posted by The Jargon File
    Microsoft Windows - A thirty-two bit extension and graphical shell to a sixteen-bit patch to an eight-bit operating system originally coded for a four-bit microprocessor which was written by a two-bit company that can't stand one bit of competition.

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    Unregistered User Yarin's Avatar
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    Quote Originally Posted by Babkockdood View Post
    Yeah, C. strcmp() and strncmp() return 0 if two strings are equal (success). And functions like malloc() and fopen() return NULL if there's not enough memory, or if the file couldn't be opened (failure). Last time I checked, NULL == 0. I thought that was pretty weird.
    That's because strcmp() doesn't check to see whether the two strings match, it compares their lexical value. Considering you probably don't know what that means, you really should read the manual on strcmp().

    As far as malloc() goes... what else could it possibly return on failure?

    Also, I would disagree about NULL != 0. In C(++) they are quite the same thing, often times even semantically. Calling zero, null, only implies that the variable holding the value in question, is probably a pointer.

    EDIT: Never mind..

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    Quote Originally Posted by Babkockdood View Post
    Yeah, C. strcmp() and strncmp() return 0 if two strings are equal (success). And functions like malloc() and fopen() return NULL if there's not enough memory, or if the file couldn't be opened (failure). Last time I checked, NULL == 0. I thought that was pretty weird.
    NULL isn't 0 ... it's a pointer to 0... look it up!

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    C++ Witch laserlight's Avatar
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    Quote Originally Posted by CommonTater
    NULL isn't 0 ... it's a pointer to 0... look it up!
    *facepalm*

    You should take your own advice...
    C: What is NULL and how is it defined?
    C++: Should I use NULL or 0?
    C + C++ Compiler: MinGW port of GCC
    Version Control System: Bazaar

    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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    (?<!re)tired Mario F.'s Avatar
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    >> Also, I would disagree about NULL != 0. In C(++) they are quite the same thing, often times even semantically.[/quote]

    So, you are saying it's quite alright to write:

    if (myClass == 0) do_something();

    Maybe the word "semantics" has a different meaning to you and me. Coincidentally, this is an old, old, old, debate that I have no wish of starting with you. So if your answer to the above code is "that is perfectly alright", suit yourself.

    >> Calling zero, null, only implies that the variable holding the value in question, is probably a pointer.

    Ah!... I love the smell of uncertainty in the strongly-typed morning.
    Last edited by Mario F.; 07-25-2011 at 10:34 PM.
    quzah likes this.
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  10. #10
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by Mario F.
    So, you are saying it's quite alright to write:

    if (myClass == 0) do_something();
    Maybe, maybe not. It depends on what is myClass. If it is a class name, then that would result in a syntax error, so the answer to your question becomes blatantly obvious.

    Quote Originally Posted by Mario F.
    Ah!... I love the smell of Probably in the strongly-typed morning.
    nullptr FTW!
    C + C++ Compiler: MinGW port of GCC
    Version Control System: Bazaar

    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  11. #11
    Registered User whiteflags's Avatar
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    Quote Originally Posted by Babkockdood View Post
    ...how when some functions return 0, it was a success, yet when others return NULL, it's a failure?
    The same reason you can safely use a 0 for different things sometimes, but you can't safely dereference NULL ever. The rules for NULL aren't only a convention like returning 0 for success is.

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    Quote Originally Posted by laserlight View Post
    *facepalm*

    You should take your own advice...
    C: What is NULL and how is it defined?
    C++: Should I use NULL or 0?
    Ahem... from stdio.h, Pelles C ver 6.50 rc4...
    Code:
    /* macros */
    #ifndef NULL
    #define NULL  ((void *)0)
    #endif
    Need it made any plainer?

  13. #13
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by CommonTater View Post
    Ahem... from stdio.h, Pelles C ver 6.50 rc4...
    Code:
    /* macros */
    #ifndef NULL
    #define NULL  ((void *)0)
    #endif
    Need it made any plainer?
    Only to ask why you think that's a pointer to zero, since it so obviously isn't.

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    Quote Originally Posted by tabstop View Post
    Only to ask why you think that's a pointer to zero, since it so obviously isn't.
    You mean like "it's a macro that expands to a void pointer to 0"... like that?

  15. #15
    and the Hat of Guessing tabstop's Avatar
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    It's not that either. It is the value 0, cast to a void*. It doesn't point to 0; it doesn't point anywhere (that is, after all, the point of NULL).

    (Edit to add: If you want to say that, in the case of a pointer, "having the value of" and "pointing to" are the same thing (i.e.
    Code:
    void *x = 0x100;
    where x has the value 0x100 and points to 0x100), that would be fine; however, that's not where we started this sidetrack....)
    Last edited by tabstop; 07-26-2011 at 06:53 AM.

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