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    SubjectRe: [PATCH 1/1] UML: fix missing non-blocking I/O, now DEBUG_SHIRQ works
    On Tue, Jun 12, 2007 at 01:39:25AM +0300, Eduard-Gabriel Munteanu wrote:
    > The cast isn't done right. Doing "fd = (long) dev_id;" doesn't help,
    > since you pass fd to mconsole_get_request() as is. And
    > mconsole_get_request() expects an integer:
    > int mconsole_get_request(int fd, struct mc_request *req)

    gcc will trim a long to an integer correctly. You can pass a long to
    an integer without casting.

    > This will generate at least a warning on arches where sizeof(int) !=
    > sizeof(long).

    No it won't. UML builds without warnings here on x86_64.

    > And by the way, AFAIK, GCC has the habit of breaking compatibility with
    > some userspace apps when a new GCC major version is released. And,
    > AFAIK, they're moving towards standards, so relying on GCC's
    > "guarantees" may backfire.

    The GCC guarantee I'm talking about it LP64 - I'm highly confident
    that's not changing any time soon.

    > >>You're calling glibc functions
    > >>with that fd as a parameter. On some arches, compiling will issue
    > >>warnings or simply fail.
    > >
    > >Which ones?
    > >
    >
    > An example is sparc64:
    > quote from
    > >>http://lxr.linux.no/source/include/asm-sparc64/types.h#L49

    What warnings does this produce? These are the same sizes as x86_64
    (and every other 64-bit arch that Linux runs on, I bet), where this
    code compiles without warning.

    > Really, a kmalloc() isn't such a big deal, it only happens once and
    > we're not in interrupt context.

    It's not the runtime cost - it's the extra code.

    > One the other hand, ensuring safety and
    > portability on other arches is something that needs to be taken care
    > of.

    You haven't demonstrated any safety or portability problems yet.

    Jeff

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    Work email - jdike at linux dot intel dot com
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