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 <[email protected]>
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.
I implemented this to print A ::= [ ], but A ::= [ %empty ] might be
clearer.
* src/parse-simulation.c (nullable_closure): Don't generate null
nonterminal derivations as leaves.
* src/derivation.c (derivation_print_impl): Don't print seperator
spaces for null nonterminal.
* tests/counterexample.at: Update test results.
item_number is used for elements of ritem as well as indices into
ritem which is fairly confusing. Introduce item_index to represent
indices into ritem.
* src/gram.h (item_index): Introduce it for ritem indices.
* src/closure.h, src/closure.c, src/ielr.c, src/lr0.c,
* src/print-graph.c, src/state.h, src/state.h:
Replace uses of item_number with item_index where appropriate.
* src/parse_simulation.c: Fix bug in parse_state_free.
Free new_root when simulate_reduction generates zero states.
* src/parse-simulation.c, src/parse-simulation.h
(parse_state_list, parse_state_list_append): New.
* src/parse-simulation.c, src/parse-simulation.h,
* src/counterexample.c: Replace all uses of lists of parse states and
appends to parse_state_lists with the new API.
* src/derivation.h, src/derivation.c: Make derivation struct opaque.
Add derivation_list type for clarity.
(derivation_list_new): New.
(derivation_list_append): New.
(derivation_list_prepend): New.
(derivation_new_leaf): New constructor for derivations with no
children.
* src/counterexample.c, src/parse-simulation.c,
* src/parse-simulation.h: Replace uses of gl_list_t containing
derivations with derivation_list and its API.
Replace calls of dervation_new using null children with
derivation_new_leaf.
* src/parse-simulation.c: replace ps_chunk and its API with typed
versions si_chunk and deriv_chunk.
* src/parse-simlation.h, src/parse-simulation.c: Remove
parse_state_retain_deriv in favor of derivation reference counting.
* src/counterexample.c: Remove search_state_retain_deriv.
* src/parse-simulation.c: Replace reference counting with
parse_state_retain everywhere.
(free_parse_state): Make this function iterative instead of
recursive. Long parse_state chains were causing stack exhaustion.
* tests/counterexample.at: Fix expectations.
Fixes the SEGV in test 247 (counterexample.at:195): "S/R after first
token".
* src/counterexample.c: here.
* tests/counterexample.at: Fix expectations.
* src/complain.h, src/complain.c: Add support for -Wcounterexample.
* src/conflicts.c (report_counterexamples): New.
(rule_conflicts_print): Use it when -Wcounterexample is given.
* src/getargs.h, src/getargs.c: Add support for --trace=cex.
* src/main.c (main): Init and deinit counterexample generation.
