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    SubjectRe: p = kmalloc(sizeof(*p), )
    Hi Russell,

    On Tue, 20 Sep 2005, Russell King wrote:
    > Think about it some more. You've added a new member to struct foo.
    > You want to fix up all the places which allocate struct foo to
    > initialise this new member. Grepping for 'struct foo' returns 100
    > files. Grepping for kmalloc in those 100 files returns 100 files.
    > Do you open all 100 in an editor and manually try and locate the five
    > kmalloc instances of this structure, and end up missing some.

    Nope. I grep for assignments to other members of that struct.

    On Tue, 20 Sep 2005, Russell King wrote:
    > Or do you do the sane thing and use kmalloc(sizeof(struct foo), ...)
    > and grep for "kmalloc[[:space:]]*(sizeof[[:space:]]*(struct foo)"
    > which returns only the five files and fix those up with knowledge
    > that you've found all the instances?

    There are still statically allocated structs left. So neither heuristic
    for figuring out initialization points is perfect.

    On 9/18/05, Russell King <> wrote:
    > Such shuffling around should be done in easy to review stages so that
    > bugs can be found, and not a mega patch. This inherently means that
    > for a structure name change, you don't end up with a new structure
    > named the same as an old structure. And if you compile-test the
    > stages, you find out if you missed the problem.

    No disagreement here.

    On 9/18/05, Russell King <> wrote:
    > Your solution is better if the only thing you're concerned about is
    > "are we allocating enough memory for this fixed size structure".
    > It completely breaks if you are also concerned about "are we doing
    > correct initialisation" or "are we allocating enough memory for this
    > variable sized structure" both of which are far more important
    > questions.
    > *especially* when you consider that kmalloc is redzoned and therefore
    > will catch the kinds of bugs you're suggesting.

    Well, yes, but for initialization, I would prefer something like what Al
    Viro suggested. To me, initialization is a separate issue from kmalloc. I
    do get your point but I just don't think sizeof(struct foo) is the answer.

    In all completeness, I would personally prefer the following form for
    allocation and initialization which is readable, easy to get right, and
    highly greppable:

    struct foo *p = kmalloc(sizeof *p, ...);

    *p = (struct foo) {
    .bar = ...;

    Unfortunately it doesn't seem like gcc is doing such a good job with it.

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      Last update: 2005-09-20 14:22    [W:0.045 / U:8.200 seconds]
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