diff --git a/src/backends/lalr.c b/src/backends/lalr.c
index 975735a16dab016576c625d5bb541d8028b776f7..b82ef71c477128728db39d4ac72ef8d4ab0dc56c 100644
--- a/src/backends/lalr.c
+++ b/src/backends/lalr.c
@@ -91,7 +91,7 @@ static HCFChoice *new_enhanced_symbol(HLREnhGrammar *eg, const HCFChoice *sym)
HHashSet *cs = h_hashtable_get(eg->corr, sym);
if (!cs) {
- cs = h_hashset_new(arena, h_eq_symbol, h_hash_symbol);
+ cs = h_hashset_new(arena, h_eq_ptr, h_hash_ptr);
h_hashtable_put(eg->corr, sym, cs);
}
h_hashset_put(cs, esym);
@@ -208,6 +208,46 @@ static bool match_production(HLREnhGrammar *eg, HCFChoice **p,
&& state == endstate);
}
+// variant of match_production where the production lhs is a charset
+// [..x..] -> x
+static bool match_charset_production(const HLRTable *table, HLREnhGrammar *eg,
+ const HCFChoice *lhs, HCFChoice *rhs,
+ size_t endstate)
+{
+ assert(lhs->type == HCF_CHARSET);
+ assert(rhs->type == HCF_CHAR);
+
+ if(!charset_isset(lhs->charset, rhs->chr))
+ return false;
+
+ // determine the enhanced-grammar right-hand side and check end state
+ HLRTransition *t = h_hashtable_get(eg->smap, lhs);
+ assert(t != NULL);
+ return (follow_transition(table, t->from, rhs) == endstate);
+}
+
+// check wether any production for sym (enhanced-grammar) matches the given
+// (original-grammar) rhs and terminates in the given end state.
+static bool match_any_production(const HLRTable *table, HLREnhGrammar *eg,
+ const HCFChoice *sym, HCFChoice **rhs,
+ size_t endstate)
+{
+ assert(sym->type == HCF_CHOICE || sym->type == HCF_CHARSET);
+
+ if(sym->type == HCF_CHOICE) {
+ for(HCFSequence **p=sym->seq; *p; p++) {
+ if(match_production(eg, (*p)->items, rhs, endstate))
+ return true;
+ }
+ } else { // HCF_CHARSET
+ assert(rhs[0] != NULL);
+ assert(rhs[1] == NULL);
+ return match_charset_production(table, eg, sym, rhs[0], endstate);
+ }
+
+ return false;
+}
+
// desugar parser with a fresh start symbol
// this guarantees that the start symbol will not occur in any productions
HCFChoice *h_desugar_augmented(HAllocator *mm__, HParser *parser)
@@ -286,28 +326,7 @@ int h_lalr_compile(HAllocator* mm__, HParser* parser, const void* params)
HHashSet *lhss = h_hashtable_get(eg->corr, item->lhs);
assert(lhss != NULL);
H_FOREACH_KEY(lhss, HCFChoice *lhs)
- assert(lhs->type == HCF_CHOICE || lhs->type == HCF_CHARSET);
-
- bool match = false;
- if(lhs->type == HCF_CHOICE) {
- for(HCFSequence **p=lhs->seq; *p; p++) {
- HCFChoice **rhs = (*p)->items;
- if(match_production(eg, rhs, item->rhs, state)) {
- match = true;
- break;
- }
- }
- } else { // HCF_CHARSET
- assert(item->rhs[0] != NULL);
- assert(item->rhs[1] == NULL);
- assert(item->rhs[0]->type == HCF_CHAR);
- HLRTransition *t = h_hashtable_get(eg->smap, lhs);
- assert(t != NULL);
- match = (t->to == state
- && charset_isset(lhs->charset, item->rhs[0]->chr));
- }
-
- if(match) {
+ if(match_any_production(table, eg, lhs, item->rhs, state)) {
// the left-hand symbol's follow set is this production's
// contribution to the lookahead
const HStringMap *fs = h_follow(1, eg->grammar, lhs);
diff --git a/src/backends/lr.c b/src/backends/lr.c
index d9aaee72dcca6b290c486680511b0f1100d80069..fb256c0bfafa0b6c53b32307bea64f61d4885919 100644
--- a/src/backends/lr.c
+++ b/src/backends/lr.c
@@ -163,7 +163,7 @@ HLRAction *h_reduce_action(HArena *arena, const HLRItem *item)
}
// adds 'new' to the branches of 'action'
-// returns a 'action' if it is already of type HLR_CONFLICT
+// returns 'action' if it is already of type HLR_CONFLICT
// allocates a new HLRAction otherwise
HLRAction *h_lr_conflict(HArena *arena, HLRAction *action, HLRAction *new)
{
diff --git a/src/backends/lr0.c b/src/backends/lr0.c
index 1c86484e61300ec40362a9abb47105424ddff2b9..a02df9e11da52ca3835e390487062a5a76ea0a31 100644
--- a/src/backends/lr0.c
+++ b/src/backends/lr0.c
@@ -30,9 +30,9 @@ static void expand_to_closure(HCFGrammar *g, HHashSet *items)
HCFChoice *sym = item->rhs[item->mark]; // symbol after mark
// if there is a non-terminal after the mark, follow it
+ // and add items corresponding to the productions of sym
// NB: unlike LLk, we do consider HCF_CHARSET a non-terminal here
- if(sym != NULL && (sym->type==HCF_CHOICE || sym->type==HCF_CHARSET)) {
- // add items corresponding to the productions of sym
+ if(sym != NULL) {
if(sym->type == HCF_CHOICE) {
for(HCFSequence **p=sym->seq; *p; p++) {
HLRItem *it = h_lritem_new(arena, sym, (*p)->items, 0);
@@ -41,7 +41,7 @@ static void expand_to_closure(HCFGrammar *g, HHashSet *items)
h_slist_push(work, it);
}
}
- } else { // HCF_CHARSET
+ } else if(sym->type == HCF_CHARSET) {
for(unsigned int i=0; i<256; i++) {
if(charset_isset(sym->charset, i)) {
// XXX allocate these single-character symbols statically somewhere
@@ -93,8 +93,8 @@ HLRDFA *h_lr0_dfa(HCFGrammar *g)
// compute closure
// if destination is a new state:
// add it to state set
- // add transition to it
// add it to the work list
+ // add transition to it
while(!h_slist_empty(work)) {
size_t state_idx = (uintptr_t)h_slist_pop(work);
diff --git a/src/t_regression.c b/src/t_regression.c
index 4097fb6cf1a64392438e9dddb4ac17427e5e0065..faa953c8451073e556acb2eda1f1fcf48ecc2d79 100644
--- a/src/t_regression.c
+++ b/src/t_regression.c
@@ -121,13 +121,24 @@ static void test_llk_zero_end(void) {
static void test_lalr_charset_lhs(void) {
HParserBackend be = PB_LALR;
- HParser *p = h_choice(h_ch('A'), h_uint8(), NULL);
+ HParser *p = h_many(h_choice(h_sequence(h_ch('A'), h_ch('B'), NULL),
+ h_in((uint8_t*)"AB",2), NULL));
- // the above would fail to compile because of an unhandled case in trying
- // to resolve a conflict where an item's left-hand-side was an HCF_CHARSET.
+ // the above would abort because of an unhandled case in trying to resolve
+ // a conflict where an item's left-hand-side was an HCF_CHARSET.
+ // however, the compile should fail - the conflict cannot be resolved.
- g_check_parse_match(p, be, "A",1, "u0x41");
- g_check_parse_match(p, be, "B",1, "u0x42");
+ if(h_compile(p, be, NULL) == 0) {
+ g_test_message("LALR compile didn't detect ambiguous grammar");
+
+ // it says it compiled it - well, then it should parse it!
+ // (this helps us see what it thinks it should be doing.)
+ g_check_parse_match(p, be, "AA",2, "(u0x41 u0x41)");
+ g_check_parse_match(p, be, "AB",2, "((u0x41 u0x42))");
+
+ g_test_fail();
+ return;
+ }
}
static void test_cfg_many_seq(void) {