From 234103d8ec691fcd82462badce702e0dfdf52638 Mon Sep 17 00:00:00 2001
From: "Sven M. Hallberg" <pesco@khjk.org>
Date: Mon, 17 Feb 2020 14:05:23 +0100
Subject: [PATCH] remove empty follow set assertion
there is a case where fs can be empty: when reducing by lhs would lead to
certain parse failure, by means of h_nothing_p() for instance.
fixes issue 83.
---
src/backends/lalr.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/src/backends/lalr.c b/src/backends/lalr.c
index 5ba3be58..86e358b7 100644
--- a/src/backends/lalr.c
+++ b/src/backends/lalr.c
@@ -338,7 +338,10 @@ int h_lalr_compile(HAllocator* mm__, HParser* parser, const void* params)
const HStringMap *fs = h_follow(1, eg->grammar, lhs);
assert(fs != NULL);
assert(fs->epsilon_branch == NULL);
- assert(!h_stringmap_empty(fs));
+ // NB: there is a case where fs can be empty: when reducing by lhs
+ // would lead to certain parse failure, by means of h_nothing_p()
+ // for instance. in that case, the below code correctly adds no
+ // reduce action.
// for each lookahead symbol, put action into table cell
if(terminals_put(table->tmap[state], fs, action) < 0)
--
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