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Tweak recent hash-table fix

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* src/fns.c (maybe_resize_hash_table): Completely initialize the
new ‘next’ vector before allocating more vectors, as this
preserves locality a bit better and it’s safer not to leave an
uninitialized Lisp object around.  Use next_size instead of
new_size to compute new index size.
This commit is contained in:
Paul Eggert 2019-07-20 23:21:14 -07:00
parent 515afc9c15
commit 49e80e765b
1 changed files with 12 additions and 15 deletions
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27
src/fns.c
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@ -4176,19 +4176,23 @@ maybe_resize_hash_table (struct Lisp_Hash_Table *h)
}
if (new_size <= old_size)
new_size = old_size + 1;
double threshold = h->rehash_threshold;
double index_float = new_size / threshold;
EMACS_INT index_size = (index_float < INDEX_SIZE_BOUND + 1
? next_almost_prime (index_float)
: INDEX_SIZE_BOUND + 1);
if (INDEX_SIZE_BOUND < max (index_size, 2 * new_size))
error ("Hash table too large to resize");
/* Allocate all the new vectors before updating *H, to
avoid problems if memory is exhausted. larger_vecalloc
finishes computing the size of the replacement vectors. */
Lisp_Object next = larger_vecalloc (h->next, new_size - old_size, -1);
Lisp_Object next = larger_vecalloc (h->next, new_size - old_size,
INDEX_SIZE_BOUND / 2);
ptrdiff_t next_size = ASIZE (next);
for (ptrdiff_t i = old_size; i < next_size - 1; i++)
gc_aset (next, i, make_fixnum (i + 1));
gc_aset (next, next_size - 1, make_fixnum (-1));
double threshold = h->rehash_threshold;
double index_float = next_size / threshold;
EMACS_INT index_size = (index_float < INDEX_SIZE_BOUND + 1
? next_almost_prime (index_float)
: INDEX_SIZE_BOUND + 1);
if (INDEX_SIZE_BOUND < index_size)
error ("Hash table too large to resize");
Lisp_Object key_and_value
= larger_vector (h->key_and_value, 2 * (next_size - old_size),
2 * next_size);
@ -4198,13 +4202,6 @@ maybe_resize_hash_table (struct Lisp_Hash_Table *h)
h->key_and_value = key_and_value;
h->hash = hash;
h->next = next;
/* Update the free list. Do it so that new entries are added at
the end of the free list. This makes some operations like
maphash faster. */
for (ptrdiff_t i = old_size; i < next_size - 1; i++)
set_hash_next_slot (h, i, i + 1);
set_hash_next_slot (h, next_size - 1, -1);
h->next_free = old_size;
/* Rehash. */