undefined and implementation specific constructs

This is a discussion on undefined and implementation specific constructs within the C++ Programming forums, part of the General Programming Boards category; As an exercise in Barjne Strousups book he asks to make a list of five constructs which are undefined in ...

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    undefined and implementation specific constructs

    As an exercise in Barjne Strousups book he asks to make a list of five constructs which are undefined in C++ and five constructs which are implementation specific.

    I couldn't come up with five of each, but thought it would be a good resource if you could list any examples you can think of.

    Here is what I came up with from the text.
    Undfined:
    1. Overflow/Underflow
    incrementing/decrementing past the max size of the argument type.

    2. Division by Zero
    3. subexpression evaluation
    int i=f(1)+g(2);// cannot assume left to right evaluation.

    The only one I could come up with that is implementation dependant is:
    The definition of NULL;

    Feel free to add your own

  2. #2
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    Go read the language standard - there are lots

    These are implementation defined.

    The number of bits in a byte (CHAR_BIT)

    The sign of the result of % on negative integers

    The size of all non-char data types (eg sizeof(int) is 1, 2, 4, 8 depending on your machine)

    Everything about bit-fields is implementation specific

    The effect of shift left/right on negative integers

    > 3. subexpression evaluation
    That's more unspecified than undefined
    http://www.eskimo.com/~scs/C-faq/q11.33.html

    Undefined means absolutely anything, like
    array[i++] = i;
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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