Re: What's cooking in git.git (Dec 2013, #02; Fri, 6)
From: Junio C Hamano <hidden>
Date: 2016-06-15 22:59:25
Possibly related (same subject, not in this thread)
- 2016-06-15 · Re: What's cooking in git.git (Dec 2013, #02; Fri, 6) · Karsten Blees <hidden>
- 2016-06-15 · Re: What's cooking in git.git (Dec 2013, #02; Fri, 6) · Karsten Blees <hidden>
- 2016-06-15 · Re: What's cooking in git.git (Dec 2013, #02; Fri, 6) · Karsten Blees <hidden>
- 2016-06-15 · Re: What's cooking in git.git (Dec 2013, #02; Fri, 6) · Jeff King <hidden>
- 2016-06-15 · Re: What's cooking in git.git (Dec 2013, #02; Fri, 6) · Junio C Hamano <hidden>
Karsten Blees [off-list ref] writes:
quoted
* kb/fast-hashmap (2013-11-18) 14 commits (merged to 'next' on 2013-12-06 at f90be3d)Damn, a day too late :-) I found these two glitches today...is a fixup patch OK or should I do a reroll (or separate patch on top)?
A separate patch on top would be the most appropriate. People have been looking at the change since mid November, and nobody noticed the problem; having a separate fix on top is a good way to document what the specific gotcha that can be easily missed is. I think the patch you attached describes the issue well, possibly with a retitle (perhaps "hashmap.h: make sure map entries are tightly packed", or something.) Thanks.
quoted hunk
--- 8< ---Subject: [PATCH] fixup! add a hashtable implementation that supports O(1) removal Use 'unsigned int' for hash-codes everywhere. Extending 'struct hashmap_entry' with an int-sized member shouldn't waste memory on 64-bit systems. This is already documented in api-hashmap.txt, but needs '__attribute__((__packed__))' to work. Reduces e.g. struct name_entry { struct hashmap_entry ent; int namelen; char *name; }; from 32 to 24 bytes. Signed-off-by: Karsten Blees <redacted> --- hashmap.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/hashmap.h b/hashmap.h index f5b3b61..b64567b 100644 --- a/hashmap.h +++ b/hashmap.h@@ -15,7 +15,7 @@ extern unsigned int memihash(const void *buf, size_t len); /* data structures */ -struct hashmap_entry { +struct __attribute__((__packed__)) hashmap_entry { struct hashmap_entry *next; unsigned int hash; };@@ -43,7 +43,7 @@ extern void hashmap_free(struct hashmap *map, int free_entries); /* hashmap_entry functions */ -static inline void hashmap_entry_init(void *entry, int hash) +static inline void hashmap_entry_init(void *entry, unsigned int hash) { struct hashmap_entry *e = entry; e->hash = hash;