On 08/02/2012 06:15 PM, Josh Triplett wrote:

On Thu, Aug 02, 2012 at 03:04:19PM +0200, Sasha Levin wrote:

quoted

On 08/02/2012 01:23 PM, Sasha Levin wrote:

quoted

quoted

#define DEFINE_HASH_TABLE(name, length) struct hash_table name = { .count = length, .buckets = { [0 ... (length - 1)] = HLIST_HEAD_INIT } }

The limitation of this approach is that the struct hash_table variable must be 'static', which is a bit limiting - see for example the use of hashtable in 'struct user_namespace'.

What if we just use two possible decelerations? One of static structs and one for regular ones.

struct hash_table {
        size_t bits;
        struct hlist_head buckets[];
};

#define DEFINE_HASHTABLE(name, bits)                                    \
        union {                                                         \
                struct hash_table name;                                 \
                struct {                                                \
                        size_t bits;                                    \

This shouldn't use "bits", since it'll get expanded to the macro
argument.

quoted

                        struct hlist_head buckets[1 << bits];           \
                } __name;                                               \

__##name

quoted

        }

#define DEFINE_STATIC_HASHTABLE(name, bit)                              \
        static struct hash_table name = { .bits = bit,                  \
                .buckets = { [0 ... (bit - 1)] = HLIST_HEAD_INIT } }

You probably wanted to change that to [0 ... ((1 << bit) - 1)] , to
match DEFINE_HASHTABLE.

I wrote it by hand and didn't compile test, will fix all of those.

Since your definition of DEFINE_HASHTABLE would also work fine when used
statically, why not just always use that?

#define DEFINE_STATIC_HASHTABLE(name, bits) static DEFINE_HASHTABLE(name, bits) = { .name.bits = bits }

It will get defined fine, but it will be awkward to use. We'd need to pass anonymous union to all the functions that handle this hashtable, which isn't pretty.

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