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cex: fix pruning crash

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Fixes a crash on Cim's grammar.
https://lists.gnu.org/r/bison-patches/2020-05/msg00107.html

* src/state-item.c (prune_disabled_paths): Prune forward and backwards
paths in seperate passes.
(prune_forward, prune_backward): New.
(disable_state_item): Change function argument from state_item_number
to state_item.
(state_items_report): Add disabling to graph print-out.
* src/conflicts.c (find_state_item_number,
report_state_counterexamples): Add SI_DISABLED checks.
This commit is contained in:
Vincent Imbimbo
2020-05-23 11:20:46 -04:00
committed by Akim Demaille
parent 37da3c4b42
commit 50cd3f16de
2 changed files with 89 additions and 40 deletions
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117
src/state-item.c
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@@ -378,15 +378,85 @@ init_firsts (void)
}
static inline void
disable_state_item (state_item_number sin)
disable_state_item (state_item *si)
{
state_item *si = state_items + sin;
si->trans = -2;
bitset_free (si->revs);
if (si->prods)
bitset_free (si->prods);
}
/* disable all transitions and productions that can only be
* reached through this state_item.
*/
static void
prune_forward (const state_item *si)
{
gl_list_t queue =
gl_list_create (GL_LINKED_LIST, NULL, NULL, NULL, true, 1,
(const void **) &si);
while (gl_list_size (queue) > 0)
{
state_item *dsi = (state_item *) gl_list_get_at (queue, 0);
gl_list_remove_at (queue, 0);
if (dsi->trans >= 0)
gl_list_add_last (queue, state_items + dsi->trans);
if (dsi->prods)
{
bitset_iterator biter;
state_item_number sin;
BITSET_FOR_EACH (biter, dsi->prods, sin, 0)
{
const state_item *prod = state_items + sin;
bitset_reset (prod->revs, dsi - state_items);
if (bitset_empty_p (prod->revs))
gl_list_add_last (queue, prod);
}
}
if (dsi != si)
disable_state_item (dsi);
}
gl_list_free (queue);
}
/* disable all state_item paths that lead to
* si and nowhere else.
*/
static void
prune_backward (const state_item *si)
{
gl_list_t queue =
gl_list_create (GL_LINKED_LIST, NULL, NULL, NULL, true, 1,
(const void **) &si);
while (gl_list_size (queue) > 0)
{
state_item *dsi = (state_item *) gl_list_get_at (queue, 0);
gl_list_remove_at (queue, 0);
bitset_iterator biter;
state_item_number sin;
BITSET_FOR_EACH (biter, dsi->revs, sin, 0)
{
if (SI_DISABLED (sin))
continue;
state_item *rev = state_items + sin;
if (rev->prods)
{
bitset_reset (rev->prods, dsi - state_items);
if (bitset_empty_p (rev->prods))
gl_list_add_last (queue, rev);
}
else
gl_list_add_last (queue, rev);
}
if (dsi != si)
disable_state_item (dsi);
}
gl_list_free (queue);
}
/*
To make searches more efficient, we can prune away paths that are
caused by disabled transitions.
@@ -399,40 +469,9 @@ prune_disabled_paths (void)
state_item *si = state_items + i;
if (si->trans == -1 && item_number_is_symbol_number (*si->item))
{
// disable the transitions out of i
for (state_item_number j = si->trans; j != -1; j = state_items[j].trans)
disable_state_item (j);
gl_list_t queue =
gl_list_create (GL_LINKED_LIST, NULL, NULL, NULL, true, 1,
(const void **) &si);
// For each disabled transition, traverse through all state_items
// accessible through reverse transition steps, and set their
// lookaheads to the reduction items lookahead
while (gl_list_size (queue) > 0)
{
const state_item *prev = gl_list_get_at (queue, 0);
gl_list_remove_at (queue, 0);
state_item_number prev_num = prev - state_items;
bitset rsi = prev->revs;
bitset_iterator biter;
state_item_number sin;
BITSET_FOR_EACH (biter, rsi, sin, 0)
{
if (SI_TRANSITION (prev))
gl_list_add_first (queue, &state_items[sin]);
else
{
bitset p = state_items[sin].prods;
if (p)
bitset_reset (p, prev_num);
}
}
disable_state_item (prev_num);
}
gl_list_free (queue);
prune_forward (si);
prune_backward (si);
disable_state_item (si);
}
}
}
@@ -459,6 +498,12 @@ state_items_report (void)
{
state_item *si = state_items + j;
item_print (si->item, NULL, stdout);
if (SI_DISABLED (j))
{
item_print (si->item, NULL, stdout);
puts (" DISABLED");
continue;
}
puts ("");
if (si->trans >= 0)
{