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    SubjectRe: [PATCH-ugly] kmemtrace: casting a gfp_t requires __force
    * Eduard - Gabriel Munteanu (eduard.munteanu@linux360.ro) wrote:
    > On Fri, Nov 07, 2008 at 10:20:29PM +0300, Alexey Dobriyan wrote:
    > > On Fri, Nov 07, 2008 at 10:58:41AM -0800, Harvey Harrison wrote:
    > > > --- a/include/linux/kmemtrace.h
    > > > +++ b/include/linux/kmemtrace.h
    > > > @@ -34,7 +34,7 @@ static inline void kmemtrace_mark_alloc_node(enum kmemtrace_type_id type_id,
    > > > "bytes_req %lu bytes_alloc %lu gfp_flags %lu node %d",
    > > > type_id, call_site, (unsigned long) ptr,
    > > > (unsigned long) bytes_req, (unsigned long) bytes_alloc,
    > > > - (unsigned long) gfp_flags, node);
    > > > + (__force unsigned long)gfp_flags, node);
    > >
    > > gfp_t is "unsigned int" actually. These casts are bogus.
    > >
    > > Subject: How do I printk <type> correctly?
    > >
    > > If variable is of Type use printk format specifier.
    > > ---------------------------------------------------------
    > > int %d or %x
    > > unsigned int %u or %x
    > > long %ld ot %lx
    > > unsigned long %lu or %lx
    > > long long %lld or %llx
    > > unsigned long long %llu or %llx
    > > size_t %zu or %zx
    > > ssize_t %zd or %zx
    > >
    > > Raw pointer value SHOULD be printed with %p.
    > >
    > > u64 SHOULD be printed with %llu/%llx, (unsigned long long):
    > >
    > > printk("%llu", (unsigned long long)u64_var);
    > >
    > > s64 SHOULD be printed with %lld/%llx, (long long):
    > >
    > > printk("%lld", (long long)s64_var);
    > >
    > > If type is dependent on config option (sector_t), use format specifier
    > > of biggest type and explicitly cast to it.
    > >
    > > Reminder: sizeof() result is of type size_t.
    > >
    > > Thank you for your cooperation.
    >
    > Hi,
    >
    > Actually, "%zu" was the first thing that crossed my mind too. But we
    > don't want to carry such types into the probe callbacks.

    quote :
    > It's a lot
    > easier to see which u* an unsigned long fits into than it is for
    > size_t.

    why would you need to limit yourself to u8, u16, u32, u64 ?

    sizeof(size_t) tells you for sure what the size of size_t is. You can
    even export it to a trace header so that size is know when the trace is
    analyzed, neat eh ? :)

    Why would you ever want to create a macro to make typing more obscure
    and to take considerably more space on architectures where a u64 is not
    required ?

    Mathieu


    > So we take care of this inside a wrapper; the sooner, the better.
    >
    > Also take into account that debugging code usually casts pointers to
    > unsigned long. This can easily be seen by looking at _RET_IP_ definition
    > or SLAB code. I think there's a very good reason to do so, since it adds
    > opacity to something that's not supposed to be used as a pointer.
    >
    >
    > Cheers,
    > Eduard
    >

    --
    Mathieu Desnoyers
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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