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    SubjectRe: Invalid compilation without -fno-strict-aliasing
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    On Wed, Feb 26, 2003 at 04:38:10PM +0100, Horst von Brand wrote:
    > Jean Tourrilhes <jt@bougret.hpl.hp.com> said:
    > > It looks like a compiler bug to me...
    > > Some users have complained that when the following code is
    > > compiled without the -fno-strict-aliasing, the order of the write and
    > > memcpy is inverted (which mean a bogus len is mem-copied into the
    > > stream).
    > > Code (from linux/include/net/iw_handler.h) :
    > > --------------------------------------------
    > > static inline char *
    > > iwe_stream_add_event(char * stream, /* Stream of events */
    > > char * ends, /* End of stream */
    > > struct iw_event *iwe, /* Payload */
    > > int event_len) /* Real size of payload */
    > > {
    > > /* Check if it's possible */
    > > if((stream + event_len) < ends) {
    > > iwe->len = event_len;
    > > memcpy(stream, (char *) iwe, event_len);
    > > stream += event_len;
    > > }
    > > return stream;
    > > }
    > > --------------------------------------------
    > > IMHO, the compiler should have enough context to know that the
    > > reordering is dangerous. Any suggestion to make this simple code more
    > > bullet proof is welcomed.
    >
    > The compiler is free to assume char *stream and struct iw_event *iwe point
    > to separate areas of memory, due to strict aliasing.

    Which is true and which is not the problem I'm complaining about.
    Have fun...

    Jean
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