Future/bison
1
0
Fork 0
mirror of https://git.savannah.gnu.org/git/bison.git synced 2026-03-09 20:33:03 +00:00
Code Issues Packages Projects Releases Wiki Activity

cex: fix state-item pruning

Browse Source 
There were several bugs in pruning that would leave the state-item
graph in an inconsistent state which could cause crashes later on:

- Pruning now happens in one pass instead of two.

- Disabled state-items no longer prune the state-items they transition
  to if that state-item has other states that transition to it.

- State-items that transition to disabled state-items are always
  pruned even if they have productions.

Reported by Michal Bartkowiak <michal.bartkowiak@nokia.com>
https://lists.gnu.org/r/bug-bison/2021-01/msg00000.html
and Zartaj Majeed
https://github.com/akimd/bison/issues/71

* src/state-item.c (prune_forward, prune_backward): Fuse into...
(prune_state_item): this.
Adjust callers.
This commit is contained in:
Vincent Imbimbo
2021-01-23 13:25:18 -05:00
committed by Akim Demaille
parent 236b85dd28
commit 2c294c1325
2 changed files with 26 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
NEWS
View File

@@ -4,6 +4,10 @@ GNU Bison NEWS
** Bug fixes
*** Counterexample Generation
In some cases counterexample generation could crash. This is fixed.
*** GLR parsers now support %merge together with api.value.type=union.
*** C++ parsers use noexcept in more places.

59
src/state-item.c
View File

@@ -384,11 +384,10 @@ disable_state_item (state_item *si)
bitset_free (si->prods);
}
/* disable all transitions and productions that can only be
* reached through this state_item.
*/
/* Disable all state_item paths that lead to/from SI and nowhere
else. */
static void
prune_forward (const state_item *si)
prune_state_item (const state_item *si)
{
state_item_list queue =
gl_list_create (GL_LINKED_LIST, NULL, NULL, NULL, true, 1,
@@ -398,8 +397,16 @@ prune_forward (const state_item *si)
{
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 (SI_DISABLED (dsi - state_items))
continue;
if (dsi->trans >= 0 && !SI_DISABLED (dsi->trans))
{
const state_item *trans = &state_items[dsi->trans];
bitset_reset (trans->revs, dsi - state_items);
if (bitset_empty_p (trans->revs))
gl_list_add_last (queue, trans);
}
if (dsi->prods)
{
@@ -407,32 +414,15 @@ prune_forward (const state_item *si)
state_item_number sin;
BITSET_FOR_EACH (biter, dsi->prods, sin, 0)
{
if (SI_DISABLED (sin))
continue;
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)
{
state_item_list 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)
@@ -440,7 +430,9 @@ prune_backward (const state_item *si)
if (SI_DISABLED (sin))
continue;
state_item *rev = &state_items[sin];
if (rev->prods)
if (&state_items[rev->trans] == dsi)
gl_list_add_last (queue, rev);
else if (rev->prods)
{
bitset_reset (rev->prods, dsi - state_items);
if (bitset_empty_p (rev->prods))
@@ -449,16 +441,13 @@ prune_backward (const state_item *si)
else
gl_list_add_last (queue, rev);
}
if (dsi != si)
disable_state_item (dsi);
disable_state_item (dsi);
}
gl_list_free (queue);
}
/*
To make searches more efficient, we can prune away paths that are
caused by disabled transitions.
*/
/* To make searches more efficient, prune away paths that are caused
by disabled transitions. */
static void
prune_disabled_paths (void)
{
@@ -466,11 +455,7 @@ prune_disabled_paths (void)
{
state_item *si = &state_items[i];
if (si->trans == -1 && item_number_is_symbol_number (*si->item))
{
prune_forward (si);
prune_backward (si);
disable_state_item (si);
}
prune_state_item (si);
}
}