From 486fe98a9c7f751998aeb6837dabfea7ac33938d Mon Sep 17 00:00:00 2001
From: Bruce Hill <bruce@bruce-hill.com>
Date: Sat, 2 Oct 2021 12:38:42 -0700
Subject: [PATCH] Fix for left recursion error due to wrong context

---
 match.c   | 11 ++++++-----
 pattern.h |  3 ++-
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/match.c b/match.c
index 17f88bb..461148d 100644
--- a/match.c
+++ b/match.c
@@ -335,10 +335,10 @@ static match_t *match(match_ctx_t *ctx, const char *str, pat_t *pat)
         // point, it can be handled with normal recursion.
         // See: left-recursion.md for more details.
         if (str == pat->args.leftrec.at) {
-            ++pat->args.leftrec.visits;
+            pat->args.leftrec.visited = true;
             return clone_match(pat->args.leftrec.match);
         } else {
-            return match(ctx, str, pat->args.leftrec.fallback);
+            return match(pat->args.leftrec.ctx, str, pat->args.leftrec.fallback);
         }
     }
     case BP_ANYCHAR: {
@@ -631,9 +631,10 @@ static match_t *match(match_ctx_t *ctx, const char *str, pat_t *pat)
             .min_matchlen = 0, .max_matchlen = -1,
             .args.leftrec = {
                 .match = NULL,
-                .visits = 0,
+                .visited = false,
                 .at = str,
-                .fallback = ref,
+                .fallback = pat,
+                .ctx = (void*)ctx,
             },
         };
         match_ctx_t ctx2 = *ctx;
@@ -652,7 +653,7 @@ static match_t *match(match_ctx_t *ctx, const char *str, pat_t *pat)
 
         match_t *m = match(&ctx2, str, ref);
         // If left recursion was involved, keep retrying while forward progress can be made:
-        if (m && rec_op.args.leftrec.visits > 0) {
+        if (m && rec_op.args.leftrec.visited) {
             while (1) {
                 const char *prev = m->end;
                 rec_op.args.leftrec.match = m;
diff --git a/pattern.h b/pattern.h
index a1f7043..dd763d5 100644
--- a/pattern.h
+++ b/pattern.h
@@ -83,9 +83,10 @@ typedef struct pat_s {
         } capture;
         struct {
             struct match_s *match;
-            unsigned int visits;
             const char *at;
             struct pat_s *fallback;
+            void *ctx;
+            bool visited;
         } leftrec;
         struct {
             const char *start, *end, *msg;