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Only use a hash index size of 1 for tables with size 0 (bug#68244)

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This invariant was intended but insufficiently enforced which could
lead to an assertion failure.

* src/fns.c (hash_index_size): Assume size>0, and return a value >1.
(make_hash_table): Only use hash_index_size for size>0.
This commit is contained in:
Mattias Engdegård 2024-01-18 18:45:16 +01:00
parent 2c887f497c
commit ef01250ef9
1 changed files with 10 additions and 5 deletions
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15
src/fns.c
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@ -4525,9 +4525,14 @@ hash_index_size (ptrdiff_t size)
ptrdiff_t upper_bound = min (MOST_POSITIVE_FIXNUM,
min (TYPE_MAXIMUM (hash_idx_t),
PTRDIFF_MAX / sizeof (ptrdiff_t)));
ptrdiff_t index_size = size + (size >> 2); /* 1.25x larger */
/* Single-element index vectors are used iff size=0. */
eassert (size > 0);
ptrdiff_t lower_bound = 2;
ptrdiff_t index_size = size + max (size >> 2, 1); /* 1.25x larger */
if (index_size < upper_bound)
index_size = next_almost_prime (index_size);
index_size = (index_size < lower_bound
? lower_bound
: next_almost_prime (index_size));
if (index_size > upper_bound)
error ("Hash table too large");
return index_size;
@ -4565,15 +4570,13 @@ make_hash_table (const struct hash_table_test *test, EMACS_INT size,
h->weakness = weak;
h->count = 0;
h->table_size = size;
int index_size = hash_index_size (size);
h->index_size = index_size;
if (size == 0)
{
h->key_and_value = NULL;
h->hash = NULL;
h->next = NULL;
eassert (index_size == 1);
h->index_size = 1;
h->index = (hash_idx_t *)empty_hash_index_vector;
h->next_free = -1;
}
@ -4591,6 +4594,8 @@ make_hash_table (const struct hash_table_test *test, EMACS_INT size,
h->next[i] = i + 1;
h->next[size - 1] = -1;
int index_size = hash_index_size (size);
h->index_size = index_size;
h->index = hash_table_alloc_bytes (index_size * sizeof *h->index);
for (ptrdiff_t i = 0; i < index_size; i++)
h->index[i] = -1;