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    SubjectRe: Invalid compilation without -fno-strict-aliasing
    Date
    In article <20030225234646.GB30611@bougret.hpl.hp.com>,
    Jean Tourrilhes <jt@bougret.hpl.hp.com> wrote:
    >
    > It looks like a compiler bug to me...

    Why do you think the kernel uses "-fno-strict-aliasing"?

    The gcc people are more interested in trying to find out what can be
    allowed by the c99 specs than about making things actually _work_. The
    aliasing code in particular is not even worth enabling, it's just not
    possible to sanely tell gcc when some things can alias.

    > 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).

    The "problem" is that we inline the memcpy(), at which point gcc won't
    care about the fact that it can alias, so they'll just re-order
    everything and claim it's out own fault. Even though there is no sane
    way for us to even tell gcc about it.

    I tried to get a sane way a few years ago, and the gcc developers really
    didn't care about the real world in this area. I'd be surprised if that
    had changed, judging by the replies I have already seen.

    I'm not going to bother to fight it.

    Linus
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