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[ot-map] Allocate top mask bit as global bit 

Avoids undefined-shift of 32 in the following line:

  map->mask = (1u << (next_bit + bits_needed)) - (1u << next_bit)

Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=1219263
This commit is contained in:
Behdad Esfahbod 2021-08-04 11:53:27 -06:00
parent f698fe5aee
commit a150baf32c
1 changed files with 5 additions and 6 deletions
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11
src/hb-ot-map.cc
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@ -150,9 +150,8 @@ void
hb_ot_map_builder_t::compile (hb_ot_map_t &m,
const hb_ot_shape_plan_key_t &key)
{
static_assert ((!(HB_GLYPH_FLAG_DEFINED & (HB_GLYPH_FLAG_DEFINED + 1))), "");
unsigned int global_bit_mask = HB_GLYPH_FLAG_DEFINED + 1;
unsigned int global_bit_shift = hb_popcount (HB_GLYPH_FLAG_DEFINED);
unsigned int global_bit_shift = 8 * sizeof (hb_mask_t) - 1;
unsigned int global_bit_mask = 1u << global_bit_shift;
m.global_mask = global_bit_mask;
@ -205,7 +204,8 @@ hb_ot_map_builder_t::compile (hb_ot_map_t &m,
/* Allocate bits now */
unsigned int next_bit = global_bit_shift + 1;
static_assert ((!(HB_GLYPH_FLAG_DEFINED & (HB_GLYPH_FLAG_DEFINED + 1))), "");
unsigned int next_bit = hb_popcount (HB_GLYPH_FLAG_DEFINED) + 1;
for (unsigned int i = 0; i < feature_infos.length; i++)
{
@ -220,7 +220,7 @@ hb_ot_map_builder_t::compile (hb_ot_map_t &m,
/* Limit bits per feature. */
bits_needed = hb_min (HB_OT_MAP_MAX_BITS, hb_bit_storage (info->max_value));
if (!info->max_value || next_bit + bits_needed > 8 * sizeof (hb_mask_t))
if (!info->max_value || next_bit + bits_needed >= global_bit_shift)
continue; /* Feature disabled, or not enough bits. */
@ -274,7 +274,6 @@ hb_ot_map_builder_t::compile (hb_ot_map_t &m,
}
map->_1_mask = (1u << map->shift) & map->mask;
map->needs_fallback = !found;
}
feature_infos.shrink (0); /* Done with these */