Thread (27 messages) 27 messages, 3 authors, 2012-08-03

Re: [RFC 1/4] hashtable: introduce a small and naive hashtable

From: Josh Triplett <josh@joshtriplett.org>
Date: 2012-08-03 17:59:26
Also in: lkml

On Thu, Aug 02, 2012 at 11:47:01PM +0200, Sasha Levin wrote:
On 08/02/2012 10:41 PM, Josh Triplett wrote:
quoted
On Thu, Aug 02, 2012 at 07:54:42PM +0200, Sasha Levin wrote:
quoted
/* I've "preprocessed" the DEFINE macro below */
union {
	struct hash_table table;
	struct {
		size_t bits;
		struct hlist_head buckets[32];
	}
} my_hashtable;
That expansion doesn't match the macros.  Using the most recent
definitions of DEFINE_HASHTABLE and DEFINE_STATIC_HASHTABLE from above,
the definition would look something like this:

static union {
	struct hash_table my_hashtable;
	struct {
		size_t bits;
		struct hlist_head buckets[1 << 5];
	} __my_hashtable;
} = { .my_hashtable.bits = 5 };
It's different because I don't think you can do what you did above with global variables.

You won't be defining any instances of that anonymous struct, so my_hashtable won't exist anywhere.
...how strange.  The above syntax ought to work, and many other
compilers document it as legal syntax (and I thought that C1x's
anonymous structs and unions allowed it), but indeed GCC doesn't accept
it.

Fair enough; looks like consolidating the macro implementations won't
actually work.

- Josh Triplett

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