[lkml]   [2007]   [Mar]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: Style Question
    2007/3/12, David Schwartz <>:
    > > NULL has the same bit pattern as the number zero. (I'm not saying the bit
    > > pattern is all zeroes. And I am not even sure if NULL ought to
    > > have the same
    > > pattern as zero.) So C++ could use (void *)0, if it would let itself :p
    > They don't have to have the same bit pattern. There's no logical reason a
    > NULL pointer couldn't have all bits set and the number zero have all bits
    > cleared.
    > Casts are perrmited to change the bit pattern. For example '(float) 7' can
    > result in a different bit pattern than '7' and similarly '(void *) 0' can
    > result in a different bit pattern from '0'.
    > As a trivial example, consider an LP64 system. NULL will have the bit
    > pattern of 64 zero bits, while '0' will have the bit pattern of 32 zero
    > bits.
    > DS

    I agree. C99 standard just says: Pointers

    "3 An integer constant expression with the value 0, or such an
    expression cast to type void *, is called a null pointer constant. If
    a null pointer constant is converted to a pointer type, the resulting
    pointer, called a null pointer, is guaranteed to compare unequal to a
    pointer to any object or function."
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2007-03-12 14:55    [W:0.025 / U:33.872 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site