Difference between C89 and C99?

Discussion in 'C Programming' started by Jason Curl, May 3, 2005.

  1. Jason Curl

    Jason Curl Guest

    I've seen the document N869.txt and the copy I could find talks about
    C99. Is there anything that comprehensively describes the difference
    between C89 and C99? I'd like to write code to be as portable as possible.

    Jason Curl, May 3, 2005
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  2. Jason Curl

    Chris Hills Guest

    K&R 1st ed was the original C description from the 1970's
    It is now obsolete as regards being the C language specification.

    K&R 2nd Ed pub 1988 their book update to C89
    C89 is an ANSI standard from dated 1989
    C90 is the ISO version and the first International C standard
    These three should be the same. K&R were on the ANSI panel that
    produced [ANSI] C89 and that became ISO-C90

    There have been various Amendments and TC's in 93,4,5 etc

    In 1999 there was a new version of the ISO-C standard. C99.
    The problem is that despite 2 TC's to C99 there are no conforming
    compilers for it. Most are part way between C90 and C99.

    If you want to write portable C I would use C99 with A1 and the TC's It
    is where (AFAIK) most of the compilers are at. Of course it depends what
    you are writing and what sort of portability you want. For portability
    there could be far more important issues than sticking to ISO-C

    You should not be using any N*** document as these are committee working
    documents and therefore not accurate. They have been superseded by the
    published standard and will not include any/some/all changes (if any)
    after the reviews.

    Buy the standard if you want to work to it. Using an N*** document is
    like trying to write a legal document using a dictionary which may have
    an arbitrary number of spelling mistakes and incorrect definitions in

    \/\/\/\/\ Chris Hills Staffs England /\/\/\/\/\
    /\/\/ www.phaedsys.org \/\/
    Chris Hills, May 3, 2005
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  3. There's a brief listing of the new features in the Foreword of the C99
    standard. The list is reproduced on the committee's web site:


    -Larry Jones

    All girls should be shipped to Pluto--that's what I say. -- Calvin
    lawrence.jones, May 3, 2005
  4. Jason Curl

    CBFalconer Guest

    However N869 is quite adequate for most purposes, as long as you
    are willing to recognize the failings. It has the great advantage
    of having a text version, which the actual standard still fails to
    supply. A text version can be searched and manipulated with
    ordinary tools. Why ISO/ANSI refused to publish an official text
    version is beyond comprehension.
    CBFalconer, May 3, 2005
  5. Because they want to sell the PDF one to you as many times as possible?
    With their licence I can't even have a copy on my desktop and one on my
    laptop without paying twice. One of the standards (I don't remember if
    it's the C or the C++ one) won't even allow copy to clipboard, it's in
    some protected format.

    It's the same with the BSI standards, they want to charge lots of money
    for them, text would be too easy to distribute...

    (Has anyone produced a list of the differences between N869 and the
    standard? I wonder if there actually are any significant ones, or
    whether the "it's not accurate" is in fact FUD aimed at trying to sell
    the standard...)

    Personally I want my code to be portable, so I'm not knowingly using any
    extensions later than C89, there are too many compilers and libraries
    which aren't fully implementing C99 (and worse they each fail to
    implement different bits). Yes, it would be lovely if everything was up
    to date, but in the real world it isn't...

    Chris C
    Chris Croughton, May 3, 2005
  6. Jason Curl

    Eric Sosman Guest

    If ANSI sold you a text version *under the exact same
    license conditions,* would that make a difference in your
    behavior? (If you're a United States citizen you need not
    answer; there's this nice little loophole called the Fifth
    Amendment to the Constitution, which says you cannot be
    required to incriminate yourself ;-)

    This strand of the thread seems to be straying from
    topicality on comp.lang.c; comp.std.c might be a better
    Eric Sosman, May 3, 2005
  7. Jason Curl

    Default User Guest

    This has been discussed many times in the past few years. Dan Pop was
    of the opinion that N869 was just fine. There are non-trivial
    differences, but if you make a mistake here based on one of those
    differences someone will gleefully point it out. Then you can annotate
    your copy so you don't make that mistake again. Of course, Dan was of
    the opinion that he knew more C without an offical copy of the Standard
    than some did *with* one.

    Mostly we use the Standards for argumentation. I am sure some of you
    are using the Standard daily for Very Important Work. You need not tell
    me that.

    Default User, May 4, 2005
  8. Jason Curl

    Jason Curl Guest

    Probably the biggest interest is the different definitions of the
    library. I would write all syntax using C89/90 as this is guaranteed to
    work with C99 as well. The interesting bits would be what new
    libraries/functions are available in C99 that aren't in C89?

    Then using my development environment I can write functions for C99, and
    test using a configuration script that can test if a particular set up
    has a C99 implementation for a function or not.

    Thanks for all comments.
    Jason Curl, May 4, 2005
  9. Jason Curl

    Jason Curl Guest

    Does the C99 standard differentiate between what's also in C89 and
    what's new?
    Jason Curl, May 4, 2005
  10. "I'll take the Fifth." "Make mine a double!" <g>

    My own behaviour? Probably not. But having it in a proprietary format
    which allows protection does make it more difficult for those people who
    do want to copy chunks into other formats.
    Although it's not about Standard C, it's about the attitude of standards
    bodies in general. Which is probably not on topic anywhere in comp.*...

    Chris C
    Chris Croughton, May 4, 2005
  11. You keep making this claim, Chris, but I've yet to see any evidence
    from you that the implementations which do claim C99 compliance are
    not in fact conforming. I can think of at least three such implemen-
    tations being cited here:

    - Comeau C plus the Dinkumware libraries
    - Edison Design Group C plus the Dinkumware libraries
    - HP Compaq C for OpenVMS for Alpha

    Some others that claim conformance:

    - IBM C for AIX v6
    - Intel C v8, except for FP_CONTRACT, FENV_ACCESS, and
    - Lund Multiprocessor Complier Company LMPCC C99 v1.3

    EDG+Dinkumware and LMPCC have received CVSA certificates.

    So, if you have evidence that none of these is conforming, please let
    us know; and if not, you might want to try to be a little more
    accurate in your claims.

    Really, is it that much harder to say "C99 conforming implementations
    are rare"?

    Michael Wojcik

    She felt increasingly (vision or nightmare?) that, though people are
    important, the relations between them are not, and that in particular
    too much fuss has been made over marriage; centuries of carnal
    embracement, yet man is no nearer to understanding man. -- E M Forster
    Michael Wojcik, May 4, 2005
  12. Jason Curl

    CBFalconer Guest

    The worst omission known to me is the absence of vsnprintf (or
    something similar) in N869.
    CBFalconer, May 4, 2005
  13. What does "rare" mean?
    It appears that you can get a C99 conforming compiler
    for just about every platform that C programmers target.
    If you want to be *accurate*, you should say,
    "C99 conforming implementations are ubiquitous."

    I don't think that the resistance to the new standard
    has anything to do with the availability of conforming compilers.
    It's just an "olde fogyism".
    Like everybody else, C programmers fear change as they get older.
    They have resisted change and will continue to resist change
    and younger programmers will just have to work around them
    until they retire or die.
    E. Robert Tisdale, May 4, 2005
  14. I hardly think that they're "ubiquitous". I know of some platforms
    that are not likely *ever* to have a conforming C99 compiler (though
    they're not platforms that most of you are likely to use), and the
    most widespread C implementation, gcc, is not fully conforming (for
    example, variable-length arrays, complex and imaginary support, and
    inline functions are still marked as "broken", even in gcc 4.0.0).
    Keith Thompson, May 4, 2005
  15. Remind me: does the international copyright convention still allow
    'fair use' ? If so, ANSI's method of distribution would seem to be
    illegal if it prevents copying of small chunks of text.
    Mark McIntyre, May 4, 2005
  16. Because quite a lot of information is lost in translation -- much of the
    typesetting is significant (e.g., italicized terms are definitions) and
    the mathematical equations are not easily represented in plain text.
    Although it would certainly be possible to create a usable text version,
    it would require far more work than the volunteer editor is willing to

    -Larry Jones

    I've got an idea for a sit-com called "Father Knows Zilch." -- Calvin
    lawrence.jones, May 4, 2005
  17. Yes, that $18 sure adds up quick.
    Yes, there are significant changes. No, I don't know of any exhaustive

    -Larry Jones

    Bad news, Mom. I promised my soul to the Devil this afternoon. -- Calvin
    lawrence.jones, May 4, 2005
  18. No, they weren't. K is primarily a writer and presumably wasn't
    interested. R deliberately chose not to participate for fear of
    exerting undue influence on the committee.

    -Larry Jones

    Sometimes I think the surest sign that intelligent life exists elsewhere
    in the universe is that none of it has tried to contact us. -- Calvin
    lawrence.jones, May 4, 2005
  19. As far as I know it does, but I can't comment definitively.
    It's perfectly legal to distribute documents on paper, which makes it
    even more difficult to copy small chunks of text than a protected PDF
    document does. I don't think that copyright law requires the
    copyright owner to make such copying easy (but of course IANAL).

    For what it's worth, my PDF copy of the C99 standard (purchased from
    ANSI) does allow copy-and-paste.
    Keith Thompson, May 4, 2005
  20. Jason Curl

    Alan Balmer Guest

    Copy and paste from the C99 standard (legally purchased PDF copy):
    This International Standard specifies the form and establishes the
    interpretation of
    programs written in the C programming language.1) It specifies

    Maybe the C++ standard? In any case, I don't know that it would be
    illegal to prevent copying of "fair use" portions. Copy protection of
    one kind or another has been used for many years on copyrighted
    material. They might have to allow you to copy it, they don't have to
    enable you to copy it. It's up to you to figure out how. Anyway, it
    seems that "fair use" is now subservient to the DMCA.
    Alan Balmer, May 4, 2005
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