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    SubjectRe: [PATCH 1/2 v2] tracing/events: provide string with undefined size support
    On Thu, 2009-04-16 at 22:00 +0200, Frederic Weisbecker wrote:
    > Impact: less memory usage for tracing
    > This patch provides the support for dynamic size strings on
    > event tracing.
    > The key concept is to use a structure with an ending char array field of
    > undefined size and use such ability to allocate the minimal size on the ring
    > buffer to make the entry fit inside as opposite to a fixed length strings with
    > upper bound.
    > This patch provides one new macro:
    > -__ending_string(name, src)
    > This one declares the string to the structure inside TP_STRUCT__entry.
    > You need to provide the name of the string field and the source that will be
    > copied inside.
    > Two constraints: only one __ending_string() per TRACE_EVENT can be added and
    > it must be the last field to be declared. Hence the __ending prefix.
    > This macro will declare the necessary field and will also add the dynamic
    > size of the string needed for the ring buffer entry allocation.
    > It also support filtering because these strings behave essentially
    > like usual fixed length string.

    can't we simply do __string(name, src) and output something like:

    struct {
    u16 size;
    char str[0];
    } name;

    That would get rid of this __ending_ wart.

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      Last update: 2009-04-16 22:17    [W:0.021 / U:18.928 seconds]
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