From 226fcb4f2a267eb286e792812a2ca497c9d311c0 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Wed, 1 Apr 2020 22:26:56 +0900
Subject: Avoid unnecessary `nextc()` recursion.

---
 mrbgems/mruby-compiler/core/parse.y | 41 ++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 16 deletions(-)

diff --git a/mrbgems/mruby-compiler/core/parse.y b/mrbgems/mruby-compiler/core/parse.y
index 0a5eb2a7b..6a1faf4ed 100644
--- a/mrbgems/mruby-compiler/core/parse.y
+++ b/mrbgems/mruby-compiler/core/parse.y
@@ -3966,6 +3966,27 @@ static void pushback(parser_state *p, int c);
 static mrb_bool peeks(parser_state *p, const char *s);
 static mrb_bool skips(parser_state *p, const char *s);
 
+static inline int
+nextc0(parser_state *p)
+{
+  int c;
+#ifndef MRB_DISABLE_STDIO
+  if (p->f) {
+    if (feof(p->f)) return -1;
+    c = fgetc(p->f);
+    if (c == EOF) return -1;
+  }
+  else
+#endif
+    if (!p->s || p->s >= p->send) {
+      return -1;
+    }
+    else {
+      c = (unsigned char)*p->s++;
+    }
+  return c;
+}
+
 static inline int
 nextc(parser_state *p)
 {
@@ -3980,30 +4001,18 @@ nextc(parser_state *p)
     cons_free(tmp);
   }
   else {
-#ifndef MRB_DISABLE_STDIO
-    if (p->f) {
-      if (feof(p->f)) goto eof;
-      c = fgetc(p->f);
-      if (c == EOF) goto eof;
-    }
-    else
-#endif
-      if (!p->s || p->s >= p->send) {
-        goto eof;
-      }
-      else {
-        c = (unsigned char)*p->s++;
-      }
+    c = nextc0(p);
+    if (c < 0) goto eof;
   }
   if (c >= 0) {
     p->column++;
   }
   if (c == '\r') {
-    const int lf = nextc(p);
+    const int lf = nextc0(p);
     if (lf == '\n') {
       return '\n';
     }
-    pushback(p, lf);
+    if (lf > 0) pushback(p, lf);
   }
   return c;
 
-- 
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