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always place at least one element in g->nts

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This commit is contained in:
Sven M. Hallberg 2013-04-28 15:21:48 +02:00
parent 3ff6de5d8a
commit 5edb4b41be
1 changed files with 13 additions and 6 deletions
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19
src/backends/ll.c
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@ -49,12 +49,19 @@ HCFGrammar *h_grammar(HAllocator* mm__, const HParser *parser)
HCFGrammar *g = h_grammar_new(mm__);
// recursively traverse the desugared form and collect all HCFChoices that
// represent a nonterminal.
// represent a nonterminal (type HCF_CHOICE or HCF_CHARSET).
collect_nts(g, desugared);
if(h_hashset_empty(g->nts)) {
// desugared is a single nonterminal. wrap it.
// XXX is this even necessary?
// desugared is a single terminal. wrap it in a singleton HCF_CHOICE.
HCFChoice *nt = h_new(HCFChoice, 1);
nt->type = HCF_CHOICE;
nt->seq = h_new(HCFSequence *, 2);
nt->seq[0] = h_new(HCFSequence, 1);
nt->seq[0]->items = h_new(HCFChoice *, 2);
nt->seq[0]->items[0] = desugared;
nt->seq[0]->items[1] = NULL;
nt->seq[1] = NULL;
h_hashset_put(g->nts, nt);
}
// XXX call collect_geneps here?
@ -91,7 +98,7 @@ static void collect_nts(HCFGrammar *grammar, HCFChoice *symbol)
}
break;
default:
default: // should not be reachable
assert_message(0, "unknown HCFChoice type");
}
}
@ -145,7 +152,7 @@ static void collect_geneps(HCFGrammar *g)
for(hte = &g->nts->contents[i]; hte; hte = hte->next) {
HCFChoice *symbol = hte->key;
// only nonterminals can derive epsilon.
// only "choice" nonterminals can derive epsilon.
if(symbol->type != HCF_CHOICE)
continue;