diff options
| author | David Lamparter <equinox@opensourcerouting.org> | 2023-04-21 16:15:11 +0200 |
|---|---|---|
| committer | David Lamparter <equinox@opensourcerouting.org> | 2023-04-21 16:27:21 +0200 |
| commit | ae19023b8e00c6a8d4ae9d631d8db15fb4924800 (patch) | |
| tree | d4f526fb9ad839daf853390adeb6b779fe553ce5 /lib/typesafe.h | |
| parent | 4dbef8567bda06418e8d1aeb566aab4d2593a65e (diff) | |
lib: typesafe hash table breadcrumbs
Looking at the coverity report, it complains that tabshift could be
zero, resulting in a uint32_t shifted by 33 (which is undefined.)
As I was confused by the "+ 1", in addition to the SA assume(), leave
some breadcumbs for next time this comes up.
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
Diffstat (limited to 'lib/typesafe.h')
| -rw-r--r-- | lib/typesafe.h | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/lib/typesafe.h b/lib/typesafe.h index 3292b6ec8b..66612be167 100644 --- a/lib/typesafe.h +++ b/lib/typesafe.h @@ -783,6 +783,12 @@ struct thash_head { struct thash_item **entries; uint32_t count; + /* tabshift can be 0 if the hash table is empty and entries is NULL. + * otherwise it will always be 2 or larger because it contains + * the shift value *plus 1*. This is a trick to make HASH_SIZE return + * the correct value (with the >> 1) for tabshift == 0, without needing + * a conditional branch. + */ uint8_t tabshift; uint8_t minshift, maxshift; }; @@ -791,8 +797,11 @@ struct thash_head { ((1U << (tabshift)) >> 1) #define HASH_SIZE(head) \ _HASH_SIZE((head).tabshift) -#define _HASH_KEY(tabshift, val) \ - ((val) >> (33 - (tabshift))) +#define _HASH_KEY(tabshift, val) \ + ({ \ + assume((tabshift) >= 2 && (tabshift) <= 33); \ + (val) >> (33 - (tabshift)); \ + }) #define HASH_KEY(head, val) \ _HASH_KEY((head).tabshift, val) #define HASH_GROW_THRESHOLD(head) \ |