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(;_;) please don't think constant `offsetof' is portable

This is a discussion on (;_;) please don't think constant `offsetof' is portable within the C++ Programming forums, part of the General Programming Boards category; This applies to C and C++. Please don't assume that just because the standard says some things about a facility ...

  1. #1
    Master Apprentice phantomotap's Avatar
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    (;_;) please don't think constant `offsetof' is portable

    This applies to C and C++.

    Please don't assume that just because the standard says some things about a facility that the real world will fit exactly.

    The `offsetof' facility is neat, but please don't use it everywhere as if it is a constant expression.

    I was just asked to help "port" some code to a new compiler that uses `offsetof' to calculate static buffer sizes.

    Most implementations of `offsetof' depend on pointer arithmetic which can't be used in a constant expression such as the side of a static buffer.

    It is not just "home grown" implementations. The statement holds for many implementations that ship with compilers.

    So again, please don't try to treat `offsetof' as a constant.

    Soma
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  2. #2
    Algorithm Dissector iMalc's Avatar
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    Better yet, avoid using offsetof if at all possible.
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    Linus Torvalds: "But it clearly is the only right way. The fact that everybody else does it some other way only means that they are wrong"

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