From eeaa0db45c3d0ab8a958893e7ce0e3f4e4a0692c Mon Sep 17 00:00:00 2001
From: "Sven M. Hallberg" <pesco@khjk.org>
Date: Tue, 11 Feb 2020 21:46:10 +0100
Subject: [PATCH] handle conflict entries in follow_transition()
fixes issue 91
---
src/backends/lalr.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/src/backends/lalr.c b/src/backends/lalr.c
index 74d37bd2..ba10e0ca 100644
--- a/src/backends/lalr.c
+++ b/src/backends/lalr.c
@@ -31,7 +31,23 @@ static size_t follow_transition(const HLRTable *table, size_t x, HCFChoice *A)
{
HLRAction *action = lrtable_lookup(table, x, A);
assert(action != NULL);
+
+ // we are interested in a transition out of state x, i.e. a shift action.
+ // while there could also be reduce actions associated with A in state x,
+ // those are not what we are here for. so if action is a conflict, search it
+ // for the shift. there will only be one and it will be the bottom element.
+ if(action->type == HLR_CONFLICT) {
+ HSlistNode *x;
+ for(x=action->branches->head; x; x=x->next) {
+ action = x->elem;
+ assert(action->type != HLR_CONFLICT); // no nesting of conflicts
+ if(action->type == HLR_SHIFT)
+ break;
+ }
+ assert(x != NULL && x->next == NULL); // shift found at the bottom
+ }
assert(action->type == HLR_SHIFT);
+
return action->nextstate;
}
--
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