From 64ed59e9224f79f6929387b8c64e9b61b5e4924f Mon Sep 17 00:00:00 2001
From: "Sven M. Hallberg" <pesco@khjk.org>
Date: Thu, 13 Feb 2020 10:31:00 +0100
Subject: [PATCH] document the resulting HCFGrammar
---
src/t_regression.c | 34 ++++++++++++++++++++++++++++++++--
1 file changed, 32 insertions(+), 2 deletions(-)
diff --git a/src/t_regression.c b/src/t_regression.c
index 7791998..3543e49 100644
--- a/src/t_regression.c
+++ b/src/t_regression.c
@@ -390,16 +390,46 @@ static void test_issue92() {
HParser *str_a = h_indirect();
HParser *str_b = h_choice(h_sequence(b, str_a, NULL), str_a, NULL);
- // h_sequence(h_optional(b), str_a, NULL); // this works
+ //h_sequence(h_optional(b), str_a, NULL); // this works
HParser *str_a_ = h_optional(h_sequence(a, str_b, NULL));
- HParser *str = str_a;//h_sequence(str_a, NULL);
+ HParser *str = str_a;
h_bind_indirect(str_a, str_a_);
+ /*
+ * grammar generated from the above:
+ *
+ * A -> B -- "augmented" with a fresh start symbol
+ * B -> C -- B = str_a
+ * | ""
+ * C -> "a" D -- C = h_sequence(a, str_b)
+ * D -> E -- D = str_b
+ * | B
+ * E -> "b" B -- E = h_sequence(b, str_a)
+ *
+ * transformed to the following "enhanced grammar":
+ *
+ * S -> 0B3
+ * 0B3 -> 0C2
+ * | ""
+ * 1B4 -> 1C2
+ * | ""
+ * 6B8 -> 6C2
+ * | "" (*) here
+ * 0C2 -> "a" 1D7
+ * 1C2 -> "a" 1D7
+ * 6C2 -> "a" 1D7
+ * 1D7 -> 1E5
+ * | 1B4
+ * 1E5 -> "b" 6B8
+ */
/*
* the following call would cause an assertion failure.
*
* assertion "!h_stringmap_empty(fs)" failed: file
* "src/backends/lalr.c", line 341, function "h_lalr_compile"
+ *
+ * the bug happens when trying to compute h_follow() for 6B8 in state 6,
+ * production "" (*).
*/
int r = h_compile(str, PB_LALR, NULL);
g_check_cmp_int(r, ==, 0);
--
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